[82]  "Mechanistic Insights into the Electrochemical Oxidation of 5-Hydroxymethylfurfural on a Thin-Film Ni Anode"

A. Prajapati, N. Govindarajan*, W. Sun, J. Huang, H. Bemana, J.  T. Feaster, S. A. Akhade, N. Kornienko*, and Christopher Hahn**

 ACS Catalysis  In Press (2024)

The electrochemical oxidation of alcohols is being explored as a favorable substitute for the oxygen evolution reaction owing to its capability to generate high-value products and lower overpotentials. Herein, we present a systematic investigation into the electrochemical oxidation of 5-hydroxymethylfurfural (HMF), a model biomass platform chemical, on a thin-film nickel catalyst, aiming to investigate the underlying reaction mechanism and shed light on the role of the catalyst’s microenvironment and phase on activity and product selectivity. Utilizing a combined experimental and computational approach, we demonstrate that NiOOH is the active phase for HMF oxidation. Additionally, we find a substantial impact of the electrochemical environment, particularly the electrolyte pH, on the reaction. Under highly alkaline conditions (pH = 13), higher activity for HMF oxidation is observed, accompanied by an increased selectivity toward 2,5-furandicarboxylic acid (FDCA) production. Conversely, a less alkaline environment (pH = 11) results in diminished HMF oxidation activity and a higher preference for the partial oxidation product 2,5-diformylfuran (DFF). Mechanistic insights from DFT studies reveal that geminal diols that are present under highly alkaline conditions undergo hydride transfer via HMFCA, while a shift to an alkoxide route occurs at a lower pH, favoring the DFF pathway. Hydride transfer energetics are also strongly affected by the surface Ni oxidation state. This integrated approach, bridging experimental and computational insights, provides a general framework for investigating the electrochemical oxidation of aldehydes and alcohols, thereby advancing rational design strategies in electrocatalysts for alcohol electro-oxidation reactions.

[81]  "Dimethylphosphite Electrosynthesis from Inorganic Phosphorus Building Blocks via Oxidative Coupling"

J. Li, H. Bemana , N Kornienko*

 RSC Sustainability In Press (2024)

Organophosphorus compounds carry importance in the chemical, medical, and fertilizer industries. Their production often entails the use of white phosphorus or PCl3, which are toxic and energetically costly to produce. In this work we investigate phosphite ester formation through an electrochemical route which has the potential to serve as a greener alternative. In particular, dimethyl phosphite was electrosynthesized through oxidative coupling of an inorganic P source, H3PO2, and methanol as a model building block with high Faradaic efficiencies approaching 100%. The reaction is proposed to proceed through electrooxidative phosphorus radical formation followed by coupling of this reactive species with proximal methanol molecules.

[80]  "Simple and Scalable Synthetic Route for Tunable Compositions of Multimetallic Oxyfluorides as Oxygen Evolution Reaction Catalysts"

A Terry, S Mathiot, A Guiet, E Boivin, Z Gohari-bajestani, V Maisonneuve, A Hémon-Ribaud, R Moury*, N Kornienko*, and J Lhoste

 ACS Applied Energy Materials In Press (2024)

This work suggests a simple and scalable synthetic route to prepare multimetallic oxyfluorides, without requiring high temperature, high pressure, and a specific atmosphere (F2, N2, Ar, vacuum, etc.). For that, tunable compositions of Ni2+–Co2+–Fe3+-based oxyfluorides Co(1–x)/2Nix/2Fe0.5O0.5F1.5 have been prepared by calcination at moderate temperature under ambient air of Co1–xNixFeF5(H2O)7 precursors, prepared beforehand through coprecipitation at room temperature, across the whole range of the solid solution (0 ≤ x ≤ 1). Structural and thermal analyses confirmed the successful substitution for both hydrated fluoride precursors and oxyfluorides. Finally, we evaluated the electrocatalytic performance of the different Ni2+–Co2+–Fe3+ oxyfluorides for oxygen evolution reaction. Among these, the trimetallic Co0.25Ni0.25Fe0.5O0.5F1.5 exhibits the lowest overpotential (290 and 370 mV respectively at 10 and 100 mA cm–2) and the highest specific activity (3.9 A m–2 at 1.53 V vs RHE). These results highlight the need for compositional tunability to maximize performance.

[79]  "Copper nanoclusters: Selective CO2 to methane conversion beyond 1 A/cm²"

M. Salehi, H.Al-Mahayni, A. Farzi, M. McKee, S. Kaviani, E. Pajootan, R. Lin, N. Kornienko, A. Seifitokaldani Applied Catalysis B In Press (2024)

Carbon dioxide offers a unique opportunity as a feedstock for energy production through electrocatalysis. Methane production holds promise for its widespread applications and market demand. However, commercial viability faces challenges of low selectivity, current density, and high applied potential. Efforts to improve methane selectivity while suppressing multi-carbon products, e.g., ethylene, often involve lower alkalinity electrolytes. However, it reduces current density due to increased ohmic resistance without significant gains in the reaction yield. This study utilizes quantum mechanics computations to design a nano-cluster copper catalyst that redirects the reaction pathway from ethylene towards methane, even under alkaline conditions. We achieved a Faradaic efficiency (FE) of 85 %, a current density of 1.5 A/cm2, and stability of over 10 hours solely by controlling particle size in copper catalysts. This work paves the way to overcoming current limitations in electrocatalytic methane production and holds broader implications for advancing sustainable CO2 utilization in energy systems.

[78]  "Enabling epoxidation and oxygen atom transfer via leveraging the water oxidation pathway"

A. Terry, and N. Kornienko*  Chem. Catalysis In Press (2024)

Electrifying energy storage and chemical processes is widely regarded as a potential route to decreasing society’s carbon footprint. While this is not a universal solution and each system must be thoroughly examined on a case-by-case basis, electrochemical routes are attractive in that they can potentially be powered by renewable sources and do not require large infrastructure to attain high temperature and elevated pressure conditions. Often times, the reactants are also abundant building blocks like H2O, N2 and CO2.

To this end, there is a growing focus on electrochemical epoxidation reactions which can use H2O as the O-source. The electrochemical epoxidation of propylene, in particular, can alleviate the need for industrially used corrosive reagents like Cl2 and peroxides. While propylene epoxidation has been previously demonstrated, catalysts used have not shown sufficient reaction rates or selectivity that would be needed in an economically viable electrolysis system. While Pt-oxides were proposed to exhibit high reactivity for propylene epoxidation, stabilizing dispersed Pt in its oxide form is difficult to achieve.

[77]  "Combined Electrochemical and Spectroscopic Investigations of Carbonate-Mediated Water Oxidation to Peroxide"

H. Bemana, and N. Kornienko*  iScience accepted (2024)

The development of electrosynthetic technologies for H2O2 production is appealing from a sustainability perspective. The use of carbon dioxide and/or carbonate species as mediators in water oxidation to peroxide has emerged as a viable route to do so but still many questions remain about the mechanism that must be addressed before practical systems emerge. To this end, this work combines electrochemical and spectroscopic methods to investigate possible reaction pathways and factors influencing the efficiency of this reaction. Our electrochemical results indicate that CO32- is the key species that undergoes electrochemical oxidation, prior to reacting with water away from the catalyst surface en route to H2O2 production. Through spectroelectrochemical infrared and Raman experiments, we noted that CO32- depletion is a key factor that limits the selectivity of the process. In turn, showed how the application of pulsed electrolysis can augment this, with an initial set of optimized parameters increasing the selectivity from 20% to 27%.  In all, this work helps pave the way for future development of practical H2O2 electrosynthetic systems.

[76]  "Carbon dioxide as a building block in heterogeneous electrosynthesis of C-X (X=N, S, P) products"

J. Li, H. Heidarpour, G. Gao, M. McKee, H. Bemana, Y. Zhang, C. T. Dinh*, A. Seifitokaldani*, and N. Kornienko*  Nature Synthesis accepted (2024)

Electrochemical CO2 reduction (CO2R) has garnered interest as a sustainable route for the production of carbon-based fuels. Against this backdrop, this perspective explores how the scope and consequent impact of CO2R can be expanded through coupling with heteroatomic co-reactants. We begin with an evaluation of societal demand for basic C-X (C-N, C-S and C-P) bond containing chemicals and a look into how they are currently synthesized. Established routes for heteroatom coupling are then contrasted with emerging electrosynthetic approaches that use CO2 as a building block, which we classify into three distinct categories. Within each identified class of electrosynthetic coupling, a critical examination pinpoints the key aspects behind the catalyst, reactor, and molecule-specific reactivity that enables the coupling pathway. The perspective is concluded with a forward-looking analysis of what catalytic chemistry needs to be developed in the context of sustainable electrosynthesis and how computational tools may accelerate the progress in a joint effort. We further discuss upcoming challenges in both system design and technoeconomic/life cycle analysis that need to be addressed as this technology matures implementation at scale. 

[75]  "Electrocatalysis with Molecules and Molecular Assemblies within Gas Diffusion Electrodes"

H. Bemana, M. McKee, *N. Kornienko Chemical Science (2023)

Molecular catalysts and their assemblies are important model systems in electrocatalysis. This is largely because their active sites, secondary coordination sphere, and reaction environment can be rationally modulated. Such experiments yield important insights into structure activity relationships that can be used to design improved catalysts or translated over to more technologically mature systems. However, in the context of electrocatalysis, molecular catalysts are often dissolved in an electrolyte or heterogenized on an electrode completely submersed in an electrolyte (e.g. H-cell), reaction setups not used in practical systems that use poorly soluble gaseous reactants like CO2, CO, or O2. This is beginning to change, with a growing emphasis placed on investigating molecular catalysts and catalytic assemblies (e.g. metal/covalent organic frameworks, polymers and more with molecular active sites) in gas-diffusion electrodes (GDEs) that feed the reactant directly from the gas phase to the catalytic sites and enable industrially viable current densities. Against this backdrop, this perspective first details the emerging set of molecular catalyst-embedded GDE-based systems and what the community has learned thus far from these efforts. We next identify gaps in knowledge and performance yet to be closed and offer strategies to explore in this direction. Finally, we conclude with a forward-looking discussion that highlights several new avenues to pursue with molecule-based GDE platforms and how this can accelerate progress in the electrocatalysis field as a whole.

[74]  "Highly Durable Nanoporous Cu2–xS Films for Efficient Hydrogen Evolution Electrocatalysis under Mild pH Conditions"

R.Fernández-Climent, J. Redondo, M.García-Tecedor, M. C. Spadaro, J. Li, D. Chartrand, F. Schiller, J. Pazos, M. F. Hurtado, V. de la Peña O’Shea, N. Kornienko, J. Arbiol, S. Barja*, C. A. Mesa*, and S.  Giménez*, ACS Catalysis (2023)

Copper-based hydrogen evolution electrocatalysts are promising materials to scale-up hydrogen production due to their reported high current densities; however, electrode durability remains a challenge. Here, we report a facile, cost-effective, and scalable synthetic route to produce Cu2–xS electrocatalysts, exhibiting hydrogen evolution rates that increase for ∼1 month of operation. Our Cu2–xS electrodes reach a state-of-the-art performance of ∼400 mA cm–2 at −1 V vs RHE under mild conditions (pH 8.6), with almost 100% Faradaic efficiency for hydrogen evolution. The rise in current density was found to scale with the electrode electrochemically active surface area. The increased performance of our Cu2–xS electrodes correlates with a decrease in the Tafel slope, while analyses by X-ray photoemission spectroscopy, operando X-ray diffraction, and in situ spectroelectrochemistry cooperatively revealed the Cu-centered nature of the catalytically active species. These results allowed us to increase fundamental understanding of heterogeneous electrocatalyst transformation and consequent structure–activity relationship. This facile synthesis of highly durable and efficient Cu2–xS electrocatalysts enables the development of competitive electrodes for hydrogen evolution under mild pH conditions.

[73]  "Hydrophobic molecular assembly at the gas-liquid-solid interface drives highly selective CO2 electromethanation"

M. McKee, M. Kutter, D. Lentz, M. Kuehnel, N. Kornienko, ChemRxiv, Nature Chemistry - In Rev. (2023)

The modularity of molecular catalysts enables the tuning of both active site and peripheral units to maximize functionality, thus rendering them as ideal model systems to explore fundamental concepts in catalysis. Hydrophobicity is often regarded as an undesirable aspect that hinders their dissolution in aqueous electrolytes. In contrast, we modified established Co terpyridine catalysts with hydrophobic perfluorinated alkyl side chains and took advantage of their hydrophobic character by utilizing them not as dissolved species in an aqueous electrolyte but at the gas-liquid-solid interfaces on a gas diffusion electrode (GDE) applied towards the electrochemical reduction of CO2. We found that the self-assembly of these perfluorinated units on the GDE surface results in a catalytic system selective for CH4 production, whereas every other Co terpyridine catalyst reported before was only selective for CO or formate. An array of mechanistic and operando spectroscopic investigations suggests a mechanism in which the pyridine units function as proton shuttles that deliver protons to the dynamic hydrophobic pocket in which CO2 reduction takes place. Finally, optimizing the system by integrating fluorinated carbon nanotubes as a hydrophobic conductive scaffold leads to a Faradaic efficiency for CH4 production above 80% at rates above 10 mA/cm2, thus far unprecedented for a molecular electrocatalytic system.

[72]  "Oxy-reductive C-N bond formation via pulsed electrolysis"

Y. Zhang, H. Al-Mahayni, P. Aguiar, D. Chartrand, M. McKee, A.Seifitokaldani, N. Kornienko, ChemRxiv, Nature Chemistry, in. rev. (2023)

Co-electrolysis of CO2 with simple N-species is an appealing route to sustainable fabrication of C-N bond containing products. A prominent challenge in, the area is to promote the C-N coupling step in place of the established CO2 reduction pathways. This can be particularly difficult when relying on solution-based species (e.g., NH3) to intercept intermediates that are continually being reduced on heterogeneous catalyst surfaces. In light of this, we introduce pulsed electrocatalysis as a tool for C-N bond formation. The reaction routes opened through this method involve both partial reduction and partial oxidation of separate reactants on the same catalyst surface in parallel to co-adsorb their activated intermediates proximal to one another. Using the CO2 and NH3 as model reactants, the end result is an enhancement of selectivity and formation rates for C-N bond containing products (urea, formamide, acetamide, methylamine) by factors of 3-20 as compared to static electrolysis in otherwise identical conditions. An array of operando measurements and computational modelling was carried out to pinpoint the key factors behind this performance enhancement. Finally, the oxy-reductive coupling strategy was extended to additional carbon and nitrogen reactants as well as applied to boost electrochemical C-S coupling.

[71]  "Feeling the Weight"

N. Kornienko, Nature Catalysis (2022)

In the context of probing electrocatalytic systems, quartz crystal microbalance measurements, initially developed in 1959, provided the base for measuring mass changes at the electrode–electrolyte interface under reaction conditions.

 [70]  "Reversible transition of an amorphous Cu-Al oxyfluoride into a highly active electrocatalyst for nitrate reduction to ammonia" Chem Catalysis (2023)

A. Guiet, A. Simonin, H. Bemana, H. Al-Mahayni, J. Li, K. Kuruvinashetti, R. Moury, A. Hémon-Ribaud,  D. Chartrand, V. Maisonneuve, J. Lhoste, A. Seifitokaldani, D. Rochefort, N. Kornienko, Chem Catalysis (2023)

The electrochemical conversion of nitrate (NO3-) to ammonia (NH3) is an emerging alternative to valorize this aqueous pollutant to an essential chemical feedstock and potential fuel. Underpinning the maturation of the field and eventual viability of this technology is the discovery of efficient electrocatalysts, coupled with fundamental insights into the reaction mechanism. Until now, fluorinated materials have not yet been explored in this direction. In this work, we present the first fluorinated catalyst used for electrochemical NO3- reduction to NH3. A new copper-based oxyfluoride, Cu3Al2OF10, prepared through a facile coprecipitation and annealing of the corresponding hydrated fluoride r-Cu3Al2F12(H2O)12, was found to be exceptionally active, attaining a NH3 Faradaic Efficiency (FE) of up to 57% for the 8-electron NO3- to NH3 pathway (-0.4 VRHE) with a mass activity of up to 1220 A.g-1 at -0.6 VRHE, the highest yet recorded. Additionally, Cu3Al2OF10 continually produced NH3 for 2.5 days while maintaining a reasonable FE (55%). Finally, electroanalytical and operando spectroscopic investigations revealed a reversible transition to a phase entailing Cu nanoparticles embedded within the amorphous oxyfluoride matrix that was predominantly responsible for the catalyst’s activity. Overall, this work stands to open avenues for transition metal fluoride materials within the field nitrogen-based electrocatalysis. 

[69]  "Electrochemical Formation of C-S Bonds from CO2 and Small Molecule Sulfur Species"

J. Li, H. Al-Mahayani, D. Chartrand, A. Seifitokaldani,  N. Kornienko, Nature Synthesis (2023)

The formation of C-S bonds is an important step in the synthesis of pharmaceutical, biological, and chemical products. A very attractive green route to C-S bond containing species would be one driven through electrocatalysis using abundant small molecule precursors but examples within this context are largely absent from the literature. To this end, this work demonstrates the use of CO2 and SO32- as cheap building blocks that couple on the surface Cu-based heterogeneous catalysts to form hydroxymethanesulfonate, sulfoacetate and methane sulfonate for the first time, with Faradaic efficiencies of up to 9.5%. A combination of operando measurements and computational modelling reveal that *CHOH formed on metallic Cu is a key electrophilic intermediate that is nucleophilically attacked by SO32- in the principal C-S bond forming step. In all, the proof-of-concept for electrocatalytic C-S bond formation and mechanistic insights gained stand to substantially broaden the scope of the emerging field of electrosynthesis.

[68]  "Construction of C–N bonds from small-molecule precursors through heterogeneous electrocatalysis"

J. Li, Y. Zhang, K. Kuruvinashetti  N. Kornienko, Nature Reviews Chemistry (2022)

Energy-intensive thermochemical processes within chemical manufacturing are a major contributor to global CO2 emissions. With the increasing push for sustainability, the scientific community is striving to develop renewable energy-powered electrochemical technologies in lieu of CO2-emitting fossil-fuel-driven methods. However, to fully electrify chemical manufacturing, it is imperative to expand the scope of electrosynthetic technologies, particularly through the innovation of reactions involving nitrogen-based reactants. This Review focuses on a rapidly emerging area, namely the formation of C–N bonds through heterogeneous electrocatalysis. The C–N bond motif is found in many fertilizers (such as urea) as well as commodity and fine chemicals (with functional groups such as amines and amides). The ability to generate C–N bonds from reactants such as CO2, NO3 or N2 would provide sustainable alternatives to the thermochemical routes used at present. We start by examining thermochemical, enzymatic and molecular catalytic systems for C–N bond formation, identifying how concepts from these can be translated to heterogeneous electrocatalysis. Next, we discuss successful heterogeneous electrocatalytic systems and highlight promising research directions. Finally, we discuss the remaining questions and knowledge gaps and thus set the trajectory for future advances in heterogeneous electrocatalytic formation of C–N bonds.

[67]  "Emerging opportunities with metal-organic framework electrosynthetic platforms"

K. Kuruvinashetti, J. Li, Y. Zhang, H. Bemana, M. McKee N. Kornienko, Chemical Physics Reviews (2022)

The development of electrochemical technologies is becoming increasingly important due to their growing part in renewable energy conversion and storage. Within this context, metal organic frameworks (MOFs) are finding an important role as electrocatalysts. Specifically, their molecularly defined structure across several lengths scales endows them functionality not accessible with conventional heterogeneous catalysts. To this end, this perspective will focus on the unique features within MOFs and their analogs that enable them to carry out electrocatalytic reactions in unique ways to synthesize fuels and value-added chemicals from abundant building blocks like CO2 and N2. We start with a brief overview of the initial advent of MOF electrocatalysts prior to moving to overview the forefront of the field of MOF-based electrosynthesis. The main discussion focuses on three principal directions in MOF-based electrosynthesis: multifunctional active sites, electronic modulation, and catalytic microenvironments. To conclude, we identify several challenges in the next stage of MOF electrocatalyst development and offer several key directions to take as the field matures.

[66]  "A Super Basic Strategy"

Y. Zhang, N. Kornienko, Joule (2022)

CO2 reduction in alkaline electrolytes enables selective multi-carbon product formation. However, spontaneous reactions between CO2 and hydroxide to form carbonate species limit energy efficiency and CO2 conversion efficiencies. Recently published in Joule, near-surface organosuperbases confer similar promotion of C2+ production in neutral media, where the carbonate issue is circumvented.

[65]  "Emerging strategies for heterogeneous small-molecule electrosynthesis"

Y. Zhang, J. Li, N. Kornienko, Cell Reports Physical Science (2021)

With an increasing global emphasis on renewable energy, electrosynthetic technologies stand to play a substantial role in generating the fuels and chemicals that power today’s society. While directions such as water electrolysis and CO2 directions have been heavily researched in the last decade, the scope of electrosynthesis can be greatly expanded to cover the full range of chemical targets that serve as building blocks for materials, pharmaceuticals, fertilizers, and more. To this end, the main challenges lie in the discovery of novel reaction routes and innovative catalytic systems that circumvent conventional limitations of electrocatalysis. Against this backdrop, this perspective will focus on the use of emerging methodologies to pioneer new electrosynthetic reaction systems. In this work, strategies of environmental control, phase change materials, reactant-selective membranes, and mediated approaches are discussed, before touching on the innovative spectroscopic approaches used to probe these systems and wrapping up with a forward-thinking outlook.

[64]  "Linker modulated peroxide electrosynthesis using metal-organic nanosheets"

K. Kuruvinashetti, N. Kornienko, ChemElectroChem (2022)

The electrochemical synthesis of hydrogen peroxide (H2O2), a widely used oxidant, is emerging as a green alternative to the conventional anthraquinone method. In this work, Ni-based metal-organic nanosheet (Ni-MONs) catalysts constructed using a variety of linkers were studied as oxygen reduction catalysts. Using a host of analytical techniques, we reveal how modulating the terephthalic acid linker with hydroxy, amine, and fluorine groups impacts the resulting physical and electronic structure of the Ni catalytic sites. These changes further impact the selectivity for H2O2, with the Ni-Amine-MON reaching near 100% Faradaic efficiency at minimal overpotential for the 2e- H2O2 pathway in alkaline electrolyte. Finally, we translate the Ni-Amine-MON catalyst to a gas-diffusion reaction geometry and demonstrate a H2O2 partial current density of 200 mA/cm2 while maintaining 85% Faradaic efficiency. In all, this study puts forth a simple route to catalyst modulation for highly effective H2O2 electrosynthesis.

[63]  "Electrocatalytic Carbon Dioxide Reduction in Acid"

J. Li, N. Kornienko, Chem Catalysis (2021)

The renewable-energy-driven conversion of CO2 is an important means of generating carbon-based fuels and chemicals to power a sustainable society. While most CO2 reduction (CO2R) is carried out in alkaline electrolyte, working in such conditions often leads to spontaneous carbonate formation and, consequently, a low energy balance and CO2 utilization rate. Alternatively, operating in acid alleviates these issues, but achieving selective CO2R in the presence of high proton concentrations has proven to be a challenge over the years. Recently, a host of works have emerged that have demonstrated both a proof of concept and initial design principles for CO2R in acid. As such, this perspective will cover the key initial findings that steer catalysis towards CO2R. After an overview of successful systems, we turn to the future in examining what key questions remain and steps can be taken in this emerging area to bring CO2R in acid toward practical feasibility.

[62]  "Highly efficient water oxidation via a bimolecular reaction mechanism on rutile structured mixed-metal oxyfluorides"

Z. Gohari-Bajestani, X.Wang, A. Guiet, R. Moury, J.-M. Grenèche, A.Hémon-Ribaud, Y. Zhang, D. Chartrand, V. Maisonneuve, A. Seifitokaldani, N. Kornienko, J. Lhoste Chem Catalysis (2022)

Mixed-metal oxides are generally considered to be the highest-performance catalysts for alkaline water oxidation. Despite significant efforts dedicated to understanding and accelerating their efficiency, most works have been limited investigations of Ni, Co, and Fe oxides, thus overlooking beneficial effects of hetero-anion incorporation. To this end, we report on the development of Co0.5Fe0.5O0.5F1.5 oxyfluoride materials featuring a rutile crystal structure and porous morphology via a scalable and green synthetic route. The catalyst surface, enhanced through electron withdrawing effects imparted by the fluoride ions, give rise to highly effective catalytic sites for electrochemical water oxidation. In particular, their performance across metrics of Tafel slope (27 mV/dec), mass activity (846 A/g at 1.53 V vs. RHE), turnover frequency (21/s at 1.53 V vs. RHE), overpotential (220 mV for 10 mA/cm2), and stability (27 days of continuous operation) largely surpasses most known Co-based catalysts. Mechanistic studies suggest that this performance is driven by a bimolecular, oxygen coupling reaction mechanism through proximal active sites on the catalyst surface, thus enabling a new avenue for achieving accelerated oxygenic electrocatalysis.

[61]  "Adaptive framework CO2 catalysis"N. Kornienko, Chem. (2021) In Press

The development of adaptive catalysts is a long-standing challenge and point of interest in the fields of chemistry, materials, and energy science. Synthetic catalysts are often limited by scaling relations, in which the intermediate-catalyst binding energies scale with respect to one another along a liner relationship. This often caps the catalyst efficiency at a certain level as the optimal point for certain reactions lies off of this line. Enzymes have long been studied as a blueprint for catalyst design, and in contrast to conventional inorganic catalysts, they feature an adaptive catalytic pocket that adapts to stabilize key reaction intermediates through interactions with amino acid residues within its hydrophobic interior. These features are a source for inspiration for the development of CO2 reduction catalysts that aim to use light and/or renewable electricity to generate carbon-based products as alternatives to fossil fuels.3 CO2 can be reduced to a wide array of possible species, and, thus, rationally steering the reaction pathway toward a particular one is key to attaining a selective catalytic system.

[60]  "Pushing the methodological envelope in understanding the photo/electro-synthetic materials-microorganism interface". K. Kuruvinashetti  N. Kornienko, iScience. (2021) In Press

Biohybrid photo/electrosynthetic systems synergize microbial metabolic pathways and inorganic materials to generate the fuels and chemicals to power our society. They aim to combine the strengths of product selectivity from biological cells and efficient charge generation and light absorption of inorganic materials. However crucial mechanistic questions still remain. In this review we address significant knowledge gaps that must be closed and recent efforts to do so to push biohybrid systems closer to applicability. In particular, we focus on significant advances that have recently been made in applying state-of-the-art analytical spectroscopic, electrochemical, and microelectronic techniques to help pinpoint key complexities of the microbe-materials interface. We discuss the basic function of these techniques, how they have been translated over to study biohybrid systems, and which key insights and implications have been extracted. Finally, we delve into the key advances necessary for the design of next generation biohybrid energy conversion systems

[59]  "C-N triple bond cleavage via trans-membrane hydrogenation" Y. Zhang, N. Kornienko, Chem Catalysis (2022)

The renewable energy-driven valorization of excess feedstocks into commodity chemicals and societally useful products constitutes a longstanding push in energy and sustainability research. To this end, this work pushes to expand the scope of green electrosynthesis by innovating a new approach to convert acetonitrile, industrially generated in excess and burned off, to in-demand ammonia and acetaldehyde products. Success here was enabled through the use of a Pd-membrane based reactor which abstracted hydrogen atoms from water, which subsequently diffused through to a separate organic compartment in which they carried out the hydrogenation reaction. In this geometry, the reaction proceeded at 5.2 mA/cm2 partial current density and 60% Faradaic efficiency towards ammonia generation. Further, the transmembrane hydrogenation approach gave rise to an onset potential of 0.2VAg/AgCl, surpassing previous state-of-the-art systems by 0.7V. A customized infrared spectroelectrochemcal setup was built up to probe the mechanism of the reaction, which was shown to proceed through an imine hydrolysis like pathway, with the hydrogenation of the NHx species that remained being the rate-limiting steps in the process. This work establishes a new route in electrochemical nitrile hydrogenation and general opens up promising avenues in green electrosynthesis.  

[58]  "Conductive metal-organic frameworks bearing M-O4 active sites as highly active biomass valorization electrocatalysts " Y. Zhang, N. Kornienko, ChemSusChem. (2021)

The electrochemical oxidation of the biomass platform 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA), is an important reaction in the emerging area of renewable energy-powered biomass valorization. A key limitation in this field is the ill-defined nature of the catalytic sites of the highest-performing materials that limits the fundamental insights that can be extracted. To this end, we report the development of a conductive metal organic framework-based electrocatalytic model system with well-defined M-O 4 active sites for electrochemical HMF oxidation. These materials were found to be highly active towards FDCA generation, with product yields of over 95%. In parallel, infrared spectroscopy was employed to capture a surface-bound aldehyde group as the key intermediate in the catalytic cycle, which forms once M(II/III) oxidation occurs. This work illustrates the advantage of utilizing molecularly defined active sites coupled with operando spectroscopy to provide fundamental insights into a variety of electrosynthetic reactions and thus paves the way for future catalyst design.

[57]  "Electrochemically Driven C-N Bond Formation from CO2 and Ammonia at the Triple-Phase Boundary " J. Li, N. Kornienko, Chem. Sci. (2022)

Electrosynthetic techniques are gaining prominence across the fields of chemistry, engineering and energy science. However, most works within the direction of synthetic heterogeneous electrocatalysis focus on water electrolysis and CO2 reduction. In this work, we moved to expand the scope of this technology by developing a synthetic scheme which couples CO2 and NH3 at a gas-liquid-solid triple-phase boundary to produce species with C-N bonds. Specifically, by bringing in CO2 from the gas phase and NH3 from the liquid phase together over solid copper catalysts, we have succeeded in forming formamide and acetamide products for the first time. In a subsequent complementary step, we have combined electrochemical analysis and a newly developed operando spectroelectrochemical method, capable of probing the aforementioned triple phase boundary, to extract an initial level of mechanistic analysis regarding the reaction pathways of these reactions and the current system’s limitations. We believe that the development and understanding of this set of reaction pathways will play an exceptionally significant role in expanding the community’s understanding of on-surface electrosynthetic reactions as well as push this set of inherently sustainable technologies towards widespread applicability.

[56]  "Probing electrosynthetic reactions with furfural on copper surfaces " J. Li, N. Kornienko, Chem. Commun. In Press (2021)

This work entails the integrated use of electrochemistry and operando Raman spectroscopy to probe the reduction of a biomass platform, furfural, to value-added chemicals on Cu electrodes. The results reveal key strutural differences of the Cu that dictate selectivity for furfuryl alcohol or 2-methylfuran

[55]  "Towards atomic precision in HMF and methane oxidation electrocatalysts " Y. Zhang, J. Li, N. Kornienko, Chem. Commun. In Press (2021)

With an increasing emphasis on transitioning to a sustainable society, electrosynthetic routes to generate fuels and chemical are rapidly gaining traction. While the electrolysis of water and CO2 has been heavily investigated over the last decade, electrocatalysis of other abundant resources such as biomass and methane are now increasingly coming into focus. As this area are relatively less mature, much work remains to be done. In particular, efforts to decipher reaction mechanisms and extract the fundamental insights are necessary to develop economically competitive electrosynthetic routes using biomass and methane. Against this backdrop, this feature article focuses on the recent developments within the community using atomically precise catalysts, both homogeneous and heterogeneous, as model systems to understand these reactions. 

[54]  "Rational incorporation of defects within metal-organic frameworks generates highly active electrocatalytic sites" N. Heidary, D. Chartrand, A. Guiet, N. Kornienko, Chem. Sci.  in press (2021)

The allure of metal-organic frameworks (MOFs) in heterogeneous electrocatalysis is that catalytically active sites may be designed a priori with an unparalleled degree of control. An emerging strategy to generate coordinatively-unsaturated active sites is through the use of organic linkers that lack a functional group that would usually bind with the metal nodes. To execute this strategy, we synthesize a model MOF, Ni-MOF-74 and incorporate a fraction of 2-hydroxyterephthalic acid in place of 2,5-dihydroxyterephthalic acid. The defective MOF, Ni74D, is evaluated vs. the nominally defect-free Ni74 MOF with a host of ex situ and in situ spectroscopic and electroanalytical techniques, using the oxidation of hydroxymethylfurtural (HMF) as a model reaction. The data indicates that Ni74D features a set of 4-coordinate Ni-O4 sites that exhibit unique vibrational signatures, redox potentials, binding motifs to HMF, and consequently superior electrocatalytic activity relative to the original Ni74 MOF, being able to convert HMF to the desired 2,5-furandicarboxylic acid at 95% yield and 80% Faradaic efficiency. Furthermore, having such rationally well-defined catalytic sites coupled with in situ Raman and infrared spectroelectrochemical measurements enabled the deduction of the reaction mechanism in which co-adsorbed *OH functions as a proton acceptor in the alcohol oxidation step and carries implications for catalyst design for heterogeneous electrosynthetic reactions en route to the electrification of the chemical industry. 

[53]  "Amorphous iron-manganese oxyfluorides, promising catalysts for Oxygen Evolution Reaction under acidic media" K. Lemoine, Z. Gohari-Bajestani, R. Moury,  A. Terry; A. Guiet, J.-M. Grenèche, A. Hémon-Ribaud, Annie, N. Heidary, V. Maisonneuve, N. Kornienko, J. Lhoste,  ACS App. Energy Mater. In Press (2021)

The development of earth-abundant catalysts for the oxygen evolution reaction (OER) in acidic media represents a significant challenge in the context of polymer electrolyte membrane (PEM) based electrolysis. In this scope, transition metal oxides constitute an emerging alternative to Ir and Ru oxides. Notably, Mn-oxides are amongst the few that have sufficient stability in acidic electrolytes, but their performance still lacks behind Ir/Ru oxides. To this end, the modification of Mn oxides’ structure, crystallinity (or amorphous structure), and/or composition may work to enhance their catalytic activity. In this report, we focused our attention on the development mixed-metal Mn-Fe based catalysts containing highly electronegative fluorine ions as acid-stable OER catalysts. Alongside of previously established MnFe2F8(H2O)2 and MnFe2F5.8O1.1 oxyfluorides, a hydrated fluoride, MnFeF5(H2O)2, was prepared by microwave-assisted solvothermal synthesis and its subsequent thermal treatment under air yielded the corresponding oxyfluoride MnFeF4.6O0.2. The resultant composition and structure of the materials were determined from powder X-Ray diffraction (XRD), Mössbauer spectrometry, thermal analyses and electronic microscopies. The crystalline hydrated fluorides (MnFeF5(H2O)2 and MnFe2F8(H2O)2) and the corresponding amorphous oxyfluorides (MnFeF4.6O0.2 and MnFe2F5.8O1.1) were subsequently evaluated for the first time as OER electrocatalysts in highly acidic (0.5M H2SO4) media. Notably, the oxyfluorides featured sustained OER activity at 10 mA/cm2 for more than 10 hours and thus, present an important addition to the growing library of earth-abundant alternatives to Ir and Ru oxides. 

[52]  "Operando spectroscopy of nanoscopic metal/covalent organic framework electrocatalysts" N. Kornienko Nanoscale In Press (2020)

Metal and covalent organic frameworks (MOFs and COFs) are increasingly finding exceptional utility in electrocatalytic systems. Their chemically defined porous nature grants them key functions that may enhance their electrocatalytic performance relative to conventional molecular or heterogeneous materials. In order to obtain insights into their function, mechanism, and dynamics under electrocatalytic conditions, operando spectroscopy, that which is performed as the catalyst is functioning, has been increasingly applied. This mini review highlights several key works emerging in recent years that have used various operando spectroscopic techniques, namely UV-vis absorption, Raman, Infrared, and X-ray absorption spectroscopy, to investigate electrocatalytic MOFs and COFs. A brief introduction to each technique and how it was applied to investigate MOF/COF-based electrolytic systems is detailed. The unique set of data obtained, interpretations made, and progress attained all point to the power of operando spectroscopy in truly opening the functionality of MOFs and COFs across many aspects of catalysis.

[51]  "Shell Isolated Nanoparticle Enhanced Raman Spectroscopy for Renewable Energy Electrocatalysis" K. Kuruvinashetti , Y. Zhang , J. Li, N. Kornienko New J. Chem. In Press (2020)

Increasing global demands for energy supply have accelerated fossil fuel consumption, triggering a gradual increase in atmospheric CO2, leading to As electrocatalytic technologies are increasingly found in the forefront of renewable energy and sustainability efforts, innovative methods are key towards extracting mechanistic information en route to understanding and consequently maximizing catalyst performance. Here, operando spectroscopy, that which is performed simultaneously as a catalyst is operating, can elucidate reaction pathways, catalyst dynamics and more. However, widely adopted methods such as surfaceenhanced Raman spectroscopy (SERS) are not compatible with the full array of relevant catalysts. To this end, shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) is emerging as an enabling technique which allows for highly sensitive Raman spectroscopy to be carried out on non-plasmonic substrates. Judicious design of plasmonic core, isolating shell and reaction parameters aided the community in the investigation of important systems such as Pt-catalysed oxygen reduction to understand the interplay of surface-active sites, reaction environment, reaction pathway, and ultimately, performance. The use of SHINERS to extract such structure-activity relationships is the focus of this review. We briefly go over the history of SERS and the advances leading up to SHINERS, provide a critical review of several state-of-the-art SHINERS works, then conclude with a perspective on growing areas in which SHINERS stands to play an important role.

[50]  "Metal-based nanomaterials for efficient CO2 electroreduction: Recent advances in mechanism, material design, and selectivity" V. C. Hoang, V. Gomes, N. Kornienko Nano Res. 78, 105311  (2020)

Increasing global demands for energy supply have accelerated fossil fuel consumption, triggering a gradual increase in atmospheric CO2, leading to adverse environmental effects of global warming, desertification and ocean acidification. Thus, reducing carbon emissions to mitigate climate change is an urgent imperative. Among several feasible strategies, electrochemical reduction of CO2 into value-added feedstocks is a promising one since such processes can be integrated with renewable electricity and powered by intermittent energy sources: wind, solar and hydro among others. The efficiency of CO2 reduction reaction (CO2RR) and its resulting economic feasibility strongly depends on the intrinsic properties of catalyst used. Several approaches have been proposed to attain high electrocatalytic performance of heterogenous electrocatalysts by controlling their size, morphology, surface defects, grain boundaries and crystal facets and by coupling with other synergistic components to synthesize nanocomposites, e.g., metallic alloys or metal/carbon-based nanomaterials. This review presents the latest achievements with metal-based nanomaterials for efficient electrochemical CO2 reduction reaction, their mechanism of action, and promising applications in selective conversions valuable chemicals/fuels, including carbon monoxide, formic acid, hydrocarbons and alcohols.

[49]  "Speeding up Nanoscience and Nanotechnology with Ultrafast Plasmonics ”N. Maccaferri, S. Meuret, N. Kornienko, D. Jariwala Nano Lett. In Press (2020)

The utilisation of inductive effects is emerging as a powerful tool to enhance material properties. Within the context of electrocatalysis, such effects may alter an active site’s electronic Surface plasmons are collective oscillations of free electrons at the interface between a conducting material and the dielectric environment. These excitations support the formation of strongly enhanced and confined electromagnetic fields. As well, they display fast dynamics lasting tens of femtoseconds and can lead to a strong nonlinear optical response at the nanoscale. Thus, they represent the perfect tool to drive and control fast optical processes, such as ultrafast optical switching, single photon emission, as well as strong coupling interactions to explore and tailor photochemical reactions. In this Virtual Issue, we gather several important papers published in Nano Letters in the past decade reporting studies on the ultrafast dynamics of surface plasmons.

[48]  "Mechanochemical synthesis of cobalt/copper fluorophosphate generates a multifunctional electrocatalyst  ”K. Lemoine N. Heidary, . Y. Inaguma, N. Kornienko Chem. Comm. In Press (2020)

The utilisation of inductive effects is emerging as a powerful tool to enhance material properties. Within the context of electrocatalysis, such effects may alter an active site’s electronic structure and consequently, its catalytic activity. To this end, we introduce catalytically active cobalt species within an electron-withdrawing copper fluorophosphate host via a mechanochemical synthetic method. The resulting mixed-metal material features exceptional performance towards electrochemical water oxidation (Ƞ of ~300 mV for 100 mA/cm2) and biomass valorisation (95% selectivity for 5-hydroxymethylfurfural to 2,5Furandicarboxylic acid conversion), thus opening avenues for the rational design of heterogeneous catalysts

[47]  "Electrochemically Triggered Dynamics Within a Hybrid Metal-Organic Electrocatalyst ” N. Heidary, M. Morency, D. Chartrand, K. H. Ly, R. Iftimie, N. Kornienko J. Am. Chem. Soc. In Press (2020)

A wide array of systems, ranging from enzymes to synthetic catalysts, exert adaptive motifs to maximize their functionality. In a related manner, select metal-organic frameworks (MOFs) and related systems exhibit structural modulations under stimuli such as the infiltration of guest species. Probing their responsive behavior in-situ is a challenging but important step towards understanding their function and subsequently building from there. In this report, we investigate the dynamic behavior of an electrocatalytic Mn-porphyrin containing MOF system (Mn-MOF). We discover, using a combination of electrochemistry and in-situ probes of UV-Vis absorption, resonance Raman and infrared spectroscopy, a restructuration of this system via a reversible cleavage of the porphyrin carboxylate ligands under an applied voltage. We further show, by combining experimental data and DFT calculations, as a proof of concept, the capacity to utilize the Mn-MOF for electrochemical CO2 fixation and to spectroscopically capture the reaction intermediates in its catalytic cycle. The findings of this work and methodology developed opens opportunities in the application of MOFs as dynamic, enzyme-inspired electrocatalytic systems.

[46]  "Operando Vibrational Spectroscopy for Electrochemical Biomass Valorization”N. Heidary, N. Kornienko Chem. Commun. In Press (2020)

Electrocatalysis is a promising route to generate fuels and value-added chemicals from abundant feedstocks powered by renewable electricity. The field of electrocatalysis research has made great progress in supplementing electrocatalyst development with operando vibrational spectroscopic techniques, those carried out simultaneously as the reaction is occurring. Such experiments unveil reaction mechanisms, structure-activity relationships and consequently, accelerate the development of next generation electrocatalytic systems. While operando techniques have now been extensively applied to water electrolysis and CO2 reduction, their application to the emerging area of biomass valorization is rather nascent. The electrocatalytic conversion of biomass can provide an alternate, environmentally friendly route to the chemicals which power our society, but this field still requires much growth before the envisioned technologies are economically competetive with thermochemical routes. Within this context, a growing body of work has began to translate the methodology and concepts from water/CO2 electrolysis to biomass valorization elucidate links between catalyst structure, adsorbed surface intermediates, and the resultant catalytic performance. The reactions of interest here include the upgrading of biomass platforms such a 5-hydroxymethylfurfural or glycerol to value-added chemicals. In this feature article we highlight these efforts and provide a critical view on the steps necessary to take to further progress the field. We further show how the knowledge derived from these studies can be translated to a plethora of other organic transformations to forge new avenues in renewable energy electrocatalysis.

[45]  "A One‐Pot Route to Faceted FePt‐Fe3O4 Dumbbells: Probing Morphology–Catalytic Activity Effects in O2 Reduction Catalysis ”K. J. Jenkinson, A. Wagner, N. Kornienko, E. Reisner, A. E. H. Wheatley Adv. Func. Mater. In Press (2020)

The design and synthesis of faceted nanoparticles with a controlled composition is of enormous importance to modern catalyst engineering. Faceted FePt‐Fe3O4 dumbbell nanoparticles are prepared by a simple, one‐pot technique that avoids the need for expensive additives or preformed seeds. The faceted product consists of an FePt octopod and a cubic Fe3O4 lobe, of mean diameter 13.6 and 14.9 nm, respectively. The mass normalized activity for electrocatalytic oxygen reduction shows that this new structure types outperforms related catalysts in alkaline media. This work illustrates the power of morphology control and tailoring crystal facet abundance at the nanoparticle surface for enhancing catalytic performance.

[44]  "Surface Chemistry Modulates CO2 Reduction Reaction Intermediates on Silver Nanoparticle Electrocatalysts ” T.G.A.A. Harris, D. Chartrand, N. Heidary, L. Prado-Perez, K. H. Ly, N. Kornienko ChemRxiv In Press (2020)

Electrocatalytic reduction of carbon dioxide (CO2R) to fuels and chemicals is a pressing scientific and engineering challenge that is, in part, hampered by a lack of understanding of the surface reaction mechanism, even for relatively simple systems. While many efforts have been dedicated to promoting CO2R on catalytic surfaces by tuning composition, morphology, and defects, the role of the reaction environment around the active site, and how this can be leveraged to modulate CO2R, is less clear. To this end, we focused on a model CO2R catalyst, Ag nanoparticles, and carried out a combined electrocatalytic and operando Raman spectroscopic investigation of CO2R on their surfaces. Bare Ag and chemically modified Ag nanoparticles were investigated to understand how the surface reaction environment dictates intermediate binding and catalytic efficiency en route to CO generation. The results revealed that the primary product on Ag is CO, which is formed through a doubly-bound CO­bridge configuration. In contrast, electrografted imidazole and polyvinylpyrrolidone (PVP)-coated Ag feature CO in a singly-bound COatop configuration on their surfaces, whereas porous zeolitic-imidazolate framework-coated Ag was observed to bind both CObridge and COatop. Further, another function of the Ag surface modifications is to dictate the type of Ag surface sites which form Ag-C bonds with CO2R intermediates. Through analysis of the of electrochemical and spectroscopic data, we deduce which key aspects of CO2R on Ag surface render a CO2R system efficient and show how surface chemistry dictates diverging CO2R surface reaction mechanisms. The insights gained here are important as they provide the community with a greater understanding of heterogeneous CO2R and can be further translated to a number of catalytic systems. `

[43]  "Disparity of cytochrome utilization in anodic and cathodic extracellular electron transfer pathways of Geobacter sulfurreducens biofilms” N. Heidary, N. Kornienko. S. Kalathil, X. Fang, K. H. Ly, H. F. Greer, E. Reisner, J. Am. Chem. Soc. In Press (2020)

Extracellular electron transfer (EET) in microorganisms is prevalent in nature and has been utilized in functional bioelectrochemical systems. EET of Geobacter sulfurreducens has been extensively studied and has been revealed to be facilitated through c-type cytochromes, which mediate charge between the electrode and G. sulfurreducens in anodic mode. However, the EET pathway of cathodic conversion of fumarate to succinate is still under debate. Here, we apply a variety of analytical methods, including electrochemistry, UV-Vis absorption and resonance Raman spectroscopy, quartz crystal microbalance with dissipation, and electron microscopy, to understand the involvement of cytochromes and other possible electron mediating species in the switching between anodic and cathodic reaction modes. Switching the applied bias for a G. sulfurreducens biofilm coupled to investigating the quantity and function of cytochromes, as well as the emergence of Fe-containing particles on the cell membrane, we provide evidence of a diminished role of cytochromes in cathodic EET. The work sheds light on the mechanisms of G. sulfurreducens biofilm growth and implies the existence of a non-heme, iron-involving EET process in cathodic mode.

[42]  "Heterogeneous Electrocatalytic Reduction of CO2 Promoted by Secondary Coordination Sphere Effects ”  J. Li*, Y. Zhang*, N. Kornienko New. J. Chem. In press (2020)

The electrochemical conversion of CO2 to fuels and chemicals is a rapidly growing area of both scientific interest and technological importance. To overcome the challenges of low rates and selectivity on heterogeneous catalysts, efforts are being directed to harness enzyme-mimetic secondary coordination sphere effects to attain a further level of control. These include  hydrogen bonding, electrostatics, complexation,  and sterics to promote CO2 reduction down a desired pathway on the electrocatalyst surface. This focus review is centered on key advances made in recent years in utilizing secondary coordination sphere effects on heterogeneous catalysts. We discuss how the incorporation rationally designed electrolyte additives, grafted surface ligands, and chemically tuneable porous scaffolds  facilitate enhanced reactivity for CO2 reduction and what advances still need to be made in order to  elevate this technology from the lab scale to economic feasibility. 

[41]  "Electrochemical Biomass Valorization on Gold-Metal Oxide Nanoscale Heterojunctions Enables Investigation of both Catalyst and Reaction Dynamics with Operando Surface-Enhanced Raman Spectroscopy ”  N. Heidary, N. Kornienko Chem. Sci.  In Press (2020)

The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging clean technology. However, mechanistic knowledge of this reaction in an electrochemical context is still lacking and operando studies are even more rare. In this work, we utilize core-shell gold-metal oxide nanostructures which enable operando surface-enhanced Raman spectroelectrochemical studies to simultaneously visualize catalyst material transformation and surface reaction intermediates under an applied voltage. As a case study, we show how the transformation of NiOOH from ~1-2 nm amorphous Ni layers facilitates the onset of HMF oxidation to 2,5-furandicarboxylic acid (FDCA), which is attained with 99% Faradaic efficiency in 1M KOH. In contrast to the case in 1M KOH, NiOOH formation is suppressed, and consequently HMF oxidation is sluggish 10 mM KOH, even at high potentials. Operando Raman experiments elucidate how surface adsorption and interaction dictates product selectivity and how the surface intermediates evolve with applied potential. We further extend our methodology to investigate NiFe, Co, Fe, and CoFe catalysts and demonstrate that high water oxidation activity is not necessarily correlated with excellent HMF oxidation performance and highlight catalytic factors important for this reaction such as reactant-surface interactions and catalysts’ physical and electronic structure. 

[40]  "Host-guest Chemistry Meets Electrocatalysis: Cucurbit[6]uril on a Au Surface as Hybrid System in CO2 Reduction”  A.Wagner, K. H. Ly, N. Heidary I. Szabo T. Foeldes, K. I. Assaf , S. J. Barrow,  K. Sokolowski, M. Al-Hada, N. Kornienko, M. F. Kuehnel, E. Rosta, I. Zebgerm W. M. Nau, O. A. Scherman, E. Reisner ACS Catal. In Press (2019)

The rational control of forming and stabilizing reaction intermediates to guide specific reaction pathways remains a major challenge in electrocatalysis. In this work, we report a surface active site engineering approach for modulating electrocatalytic CO2 reduction using the macrocycle cucurbit[6]uril (CB[6]). A pristine gold surface functionalized with CB[6] nanocavities was studied as a hybrid organic-inorganic model system that utilizes host-guest chemistry to influence the heterogeneous electrocatalytic reaction. The combination of surface-enhanced infrared absorption (SEIRA) spectroscopy and electrocatalytic experiments in conjunction with theoretical calculations support capture and reduction of CO2 inside the hydrophobic cavity of CB[6] on the gold surface in aqueous KHCO3 at negative potentials. SEIRA spectroscopic experiments show that the decoration of gold with the supramolecular host CB[6] leads to an increased local CO2 concentration close to the gold interface. Electrocatalytic CO2 reduction on a CB[6]-coated gold electrode indicates differences in the specific interactions between CO2 reduction intermediates within and outside the CB[6] molecular cavity, illustrated by a decrease in CO current density, but almost invariant H2 production compared to unfunctionalized Au. The presented methodology and mechanistic insight will guide future design of molecularly engineered catalytic environments through interfacial host-guest chemistry. 

[39]  2020 roadmap on two-dimensional nanomaterials for environmental catalysis ”  Y. Yang, M. Wu, X. Zhu, H. Xu, Si Ma, Y. Zhi, H. Xia, X. Liu, J. Pan, J.-Y. Tang, S.-P. Chai, L. Palmisano, F.  Parrino, K. Liu, J. Ma, Z.-L. Wang, L. Tan, Y.-F. Zhao, Y.-F. Song, P. Singh, P. Raizada, D. Jiang, Di Li, RA Geioushy, J.Ma, K. Zhang, S. Hu, R. Feng, G. Liu, M. Liu, Z. Li, M. Shao, N. Li, J. Peng, W.-J. Ong, N. Kornienko, Z. Xing, X. Fan, J. Ma  .  In Press (2019)

Environmental catalysis has drawn a great deal of attention due to its clean ways to produce useful chemicals or carry out some chemical processes. Photocatalysis and electrocatalysis play important roles in these fields. They can decompose and remove organic pollutants from the aqueous environment, and prepare some fine chemicals. Moreover, they also can carry out some important reactions, such as O2 reduction reaction (ORR), O2 evolution reaction (OER), H2 evolution reaction (HER), CO2 reduction reaction (CO2RR), and N2 fixation (NRR). For catalytic reactions, it is the key to develop high-performance catalysts to meet the demand for targeted reactions. In recent years, two-dimensional (2D) materials have attracted great interest in environmental catalysis due to their unique layered structures, which offer us to make use of their electronic and structural characteristics. Great progress has been made so far, including graphene, black phosphorus, oxides, layered double hydroxides (LDHs), chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks (MOFs), covalent organic frameworks (COFs), and others. This content drives us to invite many famous groups in these fields to write the roadmap on two-dimensional nanomaterials for environmental catalysis. We hope that this roadmap can give the useful guidance to researchers in future researches, and provide the research directions.

[38]  “Investigation of mixed-metal (oxy)fluorides as a new class of water oxidation electrocatalysts ” K. Lemoine, J. Lhoste, A. Ribaud, N. Heidary, V. Maisonneuve, A. Guiet, N. Kornienko Chem. Sci.  In Press (2019)

The development of electrocatalysts for the oxygen evolution reaction (OER) is one of the principal challenges in the area of renewable energy research. Within this context, mixed-metal oxides have recently emerged as the highest performing OER catalysts. Their structural and compositional modification to further boost their activity is crucial to the wide-spread use of electrolysis technologies. In this work, we investigated a series of mixed-metal F-containing materials as OER catalysts to probe possible benefits of the high electronegativity of fluoride ions. We found that crystalline hydrated fluorides, CoFe2F8(H2O)2, NiFe2F8(H2O)2, and amorphous oxyfluorides, NiFe2F4.4O1.8 and CoFe2F6.6O0.7, feature excellent activity and stability for the OER in alkaline electrolyte. Subsequent electroanalytical and spectroscopic characterization hinted that the electronic structure modulation conferred by the fluoride ions aided their reactivity. Finally, the best catalyst of the set, NiFe2F4.4O1.8, was applied as anode in an electrolyzer comprised solely of earth-abundant materials.

[37]  “Operando Raman probing of electrocatalytic biomass oxidation on gold nanoparticle surfaces ” N. Heidary, N. Kornienko Chem. Commun. In Press (2019)

Electrocatalytic conversion of biomass-derived intermediates is a green route to value-added chemicals. However, this technology is just emerging and the mechanisms of this process are not fully resolved. Here, we present the first operando Raman spectroscopic investigation of 5-hydroxymethylfurfural oxidation on gold nanoparticle sufaces, opening up avenues for understanding such reactivity and for rational systems design.

[36]  “Probing CO2 conversion chemistry on nanostructured surfaces with operando vibrational spectroscopy ” N. Heidary, K. H. Ly, N. Kornienko Nano Lett. In Press (2019)

With the rising emphasis on of renewable energy research, the field of CO2 electrocatalytic conversion to fuels has grown tremendously in recent years. Advances in nanomaterial synthesis and characterization have enabled researchers to screen effects of elemental composition, size, surface chemistry on catalyst performance. However, direct links from structure, active state to catalytic function are difficult to establish. To this end, operando spectroscopic techniques can provide key complementary information by investigating electrocatalysis under operating conditions. In particular, Raman and infrared spectroscopy have potential to reveal the identity of surface-bound intermediates, catalyst active state, and possible reaction sites to supplement the insights extracted from conventional electrochemistry. Such research aims to work in tandem synthetic and catalytic efforts to guide the development of next-generation CO2 electrocatalytic systems through rational design. In this mini-review, we examine the latest developments in operando probing of electrochemical CO2 reduction on nanostructured electrocatalysts and detail how this research accelerates the advancement of this field. 

[35]  “Advancing Techniques for Investigating the Enzyme-Electrode Interface ” N. Kornienko, K. H. Ly, W. E. Robinson, N. Heidary, J. Z. Zhang, E. Reisner Acc. Chem. Res. In Press (2019)

Complementing standard electrochemical experiments with an orthogonal set of techniques has recently allowed to provide a more complete picture of enzyme-electrode systems. Within this framework, we first discuss a brief history of achievements and challenges in enzyme electrochemistry. We subsequently describe how the aforementioned challenges can be overcome by applying advanced electrochemical techniques, quartz-crystal microbalance measurements, and spectroscopic, namely resonance Raman and infrared, analysis. For example, rotating ring disk electrochemistry allows for the simultaneous determination of reaction kinetics as well as quantification of generated products. In addition, recording changes in frequency and dissipation in a quartz crystal microbalance allows to shed light into enzyme loading, relative orientation, clustering, and denaturation at the electrode surface. Resonance Raman spectroscopy yields information on ligation and redox state of enzyme cofactors, whereas infrared spectroscopy enhances our knowledge on active site states and protein secondary and tertiary structure. The development of these emerging methods for the analysis of the enzyme-electrode interface is the primary focus of this Account. We also take a critical look at the remaining gaps in our understanding and challenges lying ahead towards attaining a complete mechanistic picture of the enzyme-electrode interface.

[34]  “Bio-inspired synthesis of reduced graphene oxide wrapped Geobacter sulfurreducens as a novel hybrid electrocatalyst for efficient oxygen evolution reaction ” S. Kalathil, K. Katuri, A. Alzami, P. Pedireddy, N. Kornienko, P. Costa, P. Saikally Chem. Mater. Accepted  (2019)

Doping of graphene or reduced graphene oxide (rGO) with heteroatoms provides a promising route for the development of electrocatalysts useful in many technologies, including water splitting. However, current doping approaches are complicated, not eco-friendly and not cost-effective. Herein, we report the synthesis of doped rGO for oxygen evolution reaction (OER) using a simple approach that is cost-effective, sustainable and easy to scale up. The OER catalyst was derived from the reduction of GO by an exo-electron transferring bacterium, Geobacter sulfurreducens. Various analytical tools indicate that OER active elements such as Fe, Cu, N, P, and S dope/decorate the rGO flakes. The hybrid catalyst (i.e., Geobacter/rGO) produces a geometric current density of 10 mA cm−2 at an overpotential of 270 mV vs. the reversible hydrogen electrode with a Tafel slope of 43 mV dec−1, and possesses high durability, evidenced through 10 hours of stability testing. Electrochemical analyses suggest the importance of Fe and its possible role as active site for OER. Overall, this work represents a simple approach towards the development of earth abundant, eco-friendly and highly active OER electrocatalyst for various applications such as solar cells, rechargeable metal-air batteries, and microbial electrosynthesis. 

[33]  “Interfacing formate dehydrogenase with metal oxides for reversible electrocatalysis or solar-driven reduction of carbon dioxide” M. Miller, W. E. Robinson, A. R. Oliveira, N. Heidary, N. Kornienko, J. Warnan, I. A. C. Pereira, E. Reisner Angew. Chemie. Int. Ed.  141, 4659 (2019)

The integration of enzymes with synthetic materials allows efficient electrocatalysis and solar fuels production. Here, we couple formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO2 reduction and report an in-depth study of the resulting enzyme-material interface. Protein film voltammetry (PFV) demonstrates stable binding of FDH in an electroactive configuration on metal oxide electrodes and reveals reversible and selective reduction of CO2 to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR IR) spectroscopy confirm a high binding affinity for FDH to the TiO2 surface. Adsorption of FDH on dye-sensitized TiO2 allows for visible-light driven CO2 reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11 ± 1 s−1. The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in selective photoreduction of aqueous CO2 to formate.

[32]  “Artificial Photosynthesis with Metal and Covalent Organic Frameworks (MOFs and COFs): Challenges and Prospects in Fuel-Forming Electrocatalysis” N. Heidary, T. G.A.A Harris. K.H. Ly, N. Kornienko  Phys. Plant. (2019)

Mimicking photosynthesis in generating chemical fuels from sunlight is a promising strategy to alleviate society’s demand for fossil fuels. However, this approach involves a number of challenges that must be overcome before this concept can emerge as a viable solution to society’s energy demand. Particularly in artificial photosynthesis, the catalytic chemistry that converts energy in the form of electricity into carbon-based fuels and chemicals has yet to be developed. Here, we describe the foundational work and future prospects of an emerging and promising class of materials: metal- and covalent-organic frameworks (MOFs and COFs). Within this context, these porous and tuneable framework materials have achieved initial success in converting abundant feedstocks (H2O and CO2) into chemicals and fuels. In this review, we first highlight key achievements in this direction. We then follow with a perspective on precisely how MOFs and COFs can perform in ways not possible with conventional molecular or heterogeneous catalysts. We conclude with a view on how spectroscopically probing MOF and COF catalysis can be used to elucidate reaction mechanisms and material dynamics throughout the course of reaction. 

[31]  “Oxygenic Photoreactivity in Photosystem II Studied by Rotating Ring Disk Electrochemistry”  N. Kornienko, J. Z. Zhang, K. Ly, K. P. Sokol, A. Fantuzzi, R. van Grondelle, A. W. Rutherford, E. Reisner J. Am. Chem. Soc. 140 (51), pp 17923–17931 (2018)

Protein film photoelectrochemistry has previously been used to monitor the activity of photosystem II, the water-plastoquinone photooxidoreductase, but the mechanistic information attainable from a three-electrode setup has remained limited. Here we introduce the four-electrode rotating ring disk electrode technique for quantifying light-driven reaction kinetics and mechanistic pathways in real time at the enzyme–electrode interface. This setup allows us to study photochemical H2O oxidation in photosystem II and to gain an in-depth understanding of pathways that generate reactive oxygen species. The results show that photosystem II reacts with O2 through two main pathways that both involve a superoxide intermediate to produce H2O2. The first pathway involves the established chlorophyll triplet-mediated formation of singlet oxygen, which is followed by its reduction to superoxide at the electrode surface. The second pathway is specific for the enzyme/electrode interface: an exposed antenna chlorophyll is sufficiently close to the electrode for rapid injection of an electron to form a highly reducing chlorophyll anion, which reacts with O2in solution to produce O2•–. Incomplete H2O oxidation does not significantly contribute to reactive oxygen formation in our conditions. The rotating ring disk electrode technique allows the chemical reactivity of photosystem II to be studied electrochemically and opens several avenues for future investigation.

[30]  “Bias-free  photoelectrochemical  water  splitting  with  photosystem II on  a  dye-sensitised  photoanode  wired  to  hydrogenase” K. P. Sokol, W. E. Robinson, J. Warnan, N. Kornienko, J. Zhang, A. Ruff. E. Reisner, Nature Energy 3, 944–951 (2018)

Semi-artificial photosynthetic systems aim to overcome the limitations of natural and artificial photosynthesis while providing an opportunity to investigate their respective functionality. The progress and studies of these hybrid systems is the focus of this forward-looking perspective. In this Review, we discuss how enzymes have been interfaced with synthetic materials and employed for semi-artificial fuel production. In parallel, we examine how more complex living cellular systems can be recruited for in vivo fuel and chemical production in an approach where inorganic nanostructures are hybridized with photosynthetic and non-photosynthetic microorganisms. Side-by-side comparisons reveal strengths and limitations of enzyme- and microorganism-based hybrid systems, and how lessons extracted from studying enzyme hybrids can be applied to investigations of microorganism-hybrid devices. We conclude by putting semi-artificial photosynthesis in the context of its own ambitions and discuss how it can help address the grand challenges facing artificial systems for the efficient generation of solar fuels and chemicals.

[29]  "Semi-artificial photosynthesis: interfacing nature’s catalytic machinery with synthetic materials" Nikolay Kornienko, Jenny Zhang, Kelsey K. Sakimoto, Peidong Yang, Erwin Reisner Nature Nanotechnology 13, 890–899 (2018)

Semi-artificial photosynthetic systems aim to overcome the limitations of natural and artificial photosynthesis while providing an opportunity to investigate their respective functionality. The progress and studies of these hybrid systems is the focus of this forward-looking perspective. In this Review, we discuss how enzymes have been interfaced with synthetic materials and employed for semi-artificial fuel production. In parallel, we examine how more complex living cellular systems can be recruited for in vivo fuel and chemical production in an approach where inorganic nanostructures are hybridized with photosynthetic and non-photosynthetic microorganisms. Side-by-side comparisons reveal strengths and limitations of enzyme- and microorganism-based hybrid systems, and how lessons extracted from studying enzyme hybrids can be applied to investigations of microorganism-hybrid devices. We conclude by putting semi-artificial photosynthesis in the context of its own ambitions and discuss how it can help address the grand challenges facing artificial systems for the efficient generation of solar fuels and chemicals.

[28] "Catalysis by design: development of a bifunctional water splitting catalyst through an operando measurement directed optimization cycle"  Nikolay Kornienko, Nina Heidary, Giannantonio Cibin, Erwin Reisner, Chemical Science, 2018, 9, 5322

A critical challenge in energy research is the development of earth abundant and cost-effective materials that catalyze the electrochemical splitting of water into hydrogen and oxygen at high rates and low overpotentials. Key to addressing this issue lies not only in the synthesis of new materials, but also in the elucidation of their active sites, their structure under operating conditions and ultimately, extraction of the structure–function relationships used to spearhead the next generation of catalyst development. In this work, we present a complete cycle of synthesis, operando characterization, and redesign of an amorphous cobalt phosphide (CoPx) bifunctional catalyst. The research was driven by integrated electrochemical analysis, Raman spectroscopy and gravimetric measurements utilizing a novel quartz crystal microbalance spectroelectrochemical cell to uncover the catalytically active species of amorphous CoPx and subsequently modify the material to enhance the activity of the elucidated catalytic phases. Illustrating the power of our approach, the second generation cobalt–iron phosphide (CoFePx) catalyst, developed through an iteration of the operando measurement directed optimization cycle, is superior in both hydrogen and oxygen evolution reactivity over the previous material and is capable of overall water electrolysis at a current density of 10 mA cm−2 with 1.5 V applied bias in 1 M KOH electrolyte solution.

[27] "Aerobic conditions enhance the photocatalytic stability of CdS/CdOx quantum dots"  David Wakerley, Khoa Ly, Nikolay Kornienko, Katherine Orchard, Moritz Kuehnel, Erwin Reisner, Chemistry: A European Journal, 24, 1-5 (2018) 

Photocatalytic H2 production through water splitting represents an attractive route to generate a renewable fuel. These systems are typically limited to anaerobic conditions due to the inhibiting effects of O2. Here, we report that sacrificial H2 evolution with CdS quantum dots does not suffer from O2 inhibition and can even be stabilised under aerobic conditions. The introduction of O2 prevents a key inactivation pathway of CdS (over‐accumulation of metallic Cd and particle agglomeration) and thereby affords particles with higher stability. These findings represent a route to exploit the O2 reduction reaction to inhibit deactivation, rather than catalysis, offering a strategy to stabilize photocatalysts that suffer from similar degradation reactions.

[26] "Solar Water Splitting with a Hydrogenase Integrated in Photoelectrochemical Tandem Cells"  Dong Heon Nam , Jenny Z. Zhang,  Virgil Andrei,  Nikolay Kornienko, Nina Heidary, Andreas Wagner,  Kenichi Nakanishi,  Katarzyna P. Sokol, Barnaby Slater, Ingo Zebger, Stephan Hofmann, Juan C. Fontecilla‐Camps, Chan Beum Park , Erwin Reisner, Angewandte Chemie, 57, 10595–10599 (2018)

Hydrogenases (H2ases) are benchmark electrocatalysts in H2 production, both in biology and (photo) catalysis in vitro. We report the tailoring of ap‐type Si photocathode for optimal loading and wiring of H2ase by the introduction of a hierarchical inverse opal (IO) TiO2 interlayer. This proton reducing Si| IO‐TiO2| H2ase photocathode is capable of driving overall water splitting in combination with a complementary photoanode. We demonstrate unassisted (bias‐free) water‐splitting by wiring Si| IO‐TiO2| H2ase to a modified BiVO4 photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si| IO‐TiO2| H2ase to a photosystem II (PSII) photoanode provides proof‐of‐concept for an engineered Z‐scheme that replaces the non‐complementary, natural light absorber photosystem I with a complementary abiotic silicon photocathode.

[25] "Efficient hydrogen peroxide generation using reduced graphene oxide-based oxygen reduction electrocatalysts"  Hyo Won Kim, Michael B Ross, Nikolay Kornienko, Liang Zhang, Jinghua Guo, Peidong Yang, Bryan D McCloskey, Nature Catalysis, 2018. 1

Electrochemical oxygen reduction has garnered attention as an emerging alternative to the traditional anthraquinone oxidation process to enable the distributed production of hydrogen peroxide. Here, we demonstrate a selective and efficient non-precious electrocatalyst, prepared through an easily scalable mild thermal reduction of graphene oxide, to form hydrogen peroxide from oxygen. During oxygen reduction, certain variants of the mildly reduced graphene oxide electrocatalyst exhibit highly selective and stable peroxide formation activity at low overpotentials (<10 mV) under basic conditions, exceeding the performance of current state-of-the-art alkaline catalysts. Spectroscopic structural characterization and in situ Raman spectroelectrochemistry provide strong evidence that sp2-hybridized carbon near-ring ether defects along sheet edges are the most active sites for peroxide production, providing new insight into the electrocatalytic design of carbon-based materials for effective peroxide production.

[24] "Enhancing Catalysis through Substitute-Driven Redox Tuning"  Nikolay Kornienko Joule 2018 2 (2), 207-209

The shift to a renewable energy powered society will ultimately be driven by the development of effective methods of energy conversion and storage. Energy is most efficiently stored in chemical bonds, and consequently, energy harvesting and storage often requires bond cleavage and formation. Catalysts speed up these reactions to minimize energy losses and voltage requirements in electrochemical processes. To this end, the discovery of efficient and cost-effective catalysts underpins the growth of technologies ranging from fuel cells and electrolyzers to metal-air batteries.

[23] "Physical Biology of the Materials–Microorganism Interface" Kelsey K Sakimoto, Nikolay Kornienko, Stefano Cestellos-Blanco, Jongwoo Lim, Chong Liu, Peidong Yang  J. Am. Chem. Soc., 2018, 140 (6), pp 1978–1985

Future solar-to-chemical production will rely upon a deep understanding of the material–microorganism interface. Hybrid technologies, which combine inorganic semiconductor light harvesters with biological catalysis to transform light, air, and water into chemicals, already demonstrate a wide product scope and energy efficiencies surpassing that of natural photosynthesis. But optimization to economic competitiveness and fundamental curiosity beg for answers to two basic questions: (1) how do materials transfer energy and charge to microorganisms, and (2) how do we design for bio- and chemocompatibility between these seemingly unnatural partners? This Perspective highlights the state-of-the-art and outlines future research paths to inform the cadre of spectroscopists, electrochemists, bioinorganic chemists, material scientists, and biologists who will ultimately solve these mysteries.

[22] Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping" T. J Jacobsson , S. Svanström, V. Andrei, J. P. H. Rivett, N. Kornienko, B. Philippe, U. B. Cappel, H. Rensmo, F. Deschler, and G. Boschloo. J. Phys. Chem. C, Article ASAP

A trend in high performing lead halide perovskite solar cell devices has been increasing compositional complexity by successively introducing more elements, dopants, and additives into the structure; and some of the latest top efficiencies have been achieved with a quadruple cation mixed halide perovskite CsxFAyMAzRb1-x-y-zPbBrqI3-q. This paper continues this trend by exploring doping of mixed lead halide perovskites, FA0.83MA0.17PbBr0.51I2.49, with an extended set of alkali cations, i.e., Cs+, Rb+, K+, and Na+, as well as combinations of them. The doped perovskites were investigated with X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, hard X-ray photoelectron spectroscopy, UV–vis, steady state fluorescence, and ultrafast transient absorption spectroscopy. Solar cell devices were made as well. Cs+ can replace the organic cations in the perovskite structure, but Rb+, K+, and Na+ do not appear to do that. Despite this, samples doped with K and Na have substantially longer fluorescence lifetimes, which potentially could be beneficial for device performance.

[21] “Reticular Electronic Tuning of Porphyrin Active Sites in Covalent Organic Frameworks for Electrocatalytic Carbon Dioxide Reduction" C. Dierks*, S. Lin*,  N. Kornienko, E. Kapustin, E. Nichols, C. Zhu, Y. Zhao, C. Chang, and O. M. Yaghi  J. Am. Chem. Soc.. 2017, 140 (3), 1116-1122

The electronic character of porphyrin active sites for electrocatalytic reduction of CO2 to CO in a two-dimensional covalent organic framework (COF) was tuned by modification of the reticular structure. Efficient charge transport along the COF backbone promotes electronic connectivity between remote functional groups and the active sites and enables the modulation of the catalytic properties of the system. A series of oriented thin films of these COFs was found to reduce CO2 to CO at low overpotential (550 mV) with high selectivity (faradaic efficiency of 87%) and at high current densities (65 mA/mg) ― a performance well beyond related molecular catalysts in regard to selectivity and efficiency. The catalysts are stable for over 12 hours without any loss in reactivity. X-ray absorption measurements on the cobalt L-edge for the modified COFs enable correlations between the inductive effects of the appended functionality and the electronic character of the reticulated molecular active sites.

[20] “Critical Role of Methylammonium Librational Motion in Methylammonium Lead Iodide (CH3NH3PbI3) Perovskite Photochemistry" M. Park*, N. Kornienko*, S. E. Reyes-Lillo, M. Lai, J. B. Neaton, P. Yang, and R. A. Mathies Nano Lett. 2017, 17 (7), pp 4151–4157

Raman and photoluminescence (PL) spectroscopy are used to investigate dynamic structure-function relationships in methylammonium lead iodide (MAPbI3) perovskite. The intensity of the 150 cm-1 methylammonium (MA) librational Raman mode is found to be correlated with PL intensities in microstructures of MAPbI3. Because of the strong hydrogen-bond between hydrogens in MA and iodine in the PbI6 perovskite octahedra, the Raman activity of MA is very sensitive to structural distortions of the inorganic framework. The structural distortions directly influence PL intensities, which in turn, have been correlated with microstructure quality. Our measurements, supported with first principles calculations, indicate how excited-state MA librational displacements mechanistically control PL efficiency and lifetime in MAPbI3 - material parameters that are likely important for efficient PV devices.

[19] “Cyborgian Material Design for Solar Fuel Production: The Emerging Photosynthetic Biohybrid Systems” K. Sakimoto, N. Kornienko, P. Yang Acc. Chem. Res.. 2017 50 (3), 476-481

Photosynthetic Biohybrid Systems (PBSs),combine the strengths of inorganic materials and biological catalysts:exploiting semiconductor broadband light absorption to capture solar energy and subsequently transform it into valuable CO2-derived chemicals by taking advantage of the metabolic pathways in living organisms. 

In this work, we first traverse through a brief history of recent PBSs, demonstrating the modularity and diversity of possible architectures to rival and, in many cases, surpass the performance of chemistry or biology alone before envisioning the future of these hybrid systems, opportunities for improvement, and its role in a sustainable living here on earth, and beyond.

[18] “Spectroscopic elucidation of energy transfer in hybrid inorganic–biological organisms for solar-to-chemical production” N. Kornienko*, K. Sakimoto*, D. Herlihy, S. Nguyen, A. P. Alivisatos, C. B. Harris, A. Schwartzberg, P. Yang Proc. Natl. Acad. Sci. 113, 42 (2016)

Solar-powered chemical production from CO2 promises to alleviate petrochemical consumption. Hybrid systems of an inorganic semiconductor light harvester and a microbial catalyst offer a viable way forward. Whereas a number of such systems have been described, the semiconductor-to-bacterium electron transfer mechanism remains largely unknown, limiting rational approaches to improving their performance. In this work, we look at how a semiconductor nanoparticle-sensitized bacterium transforms CO2 and sunlight into acetic acid, a known precursor for fuels, food, pharmaceuticals, and polymers. Using time-resolved spectroscopy and biochemical analysis, we conclude that multiple pathways facilitate electron and light energy transfer from semiconductor to bacterium. This foundational study enables future investigation, understanding, and improvement of complex biotic–abiotic hybrid systems.

In the News: LBL Highlight

[17] “Atomic Resolution Imaging of Halide Perovskites” Y. Yu, D. Zhang, C. Kisielowski, L. Dou, N. Kornienko, Y. Bekenstein, A. P. Alivisatos, P. Yang, Nano Lett. 16, 7530 (2016)

The radiation-sensitive nature of halide perovskites has hindered structural studies at the atomic scale. We overcome this obstacle by applying low dose-rate in-line holography, which combines aberration-corrected high-resolution transmission electron microscopy with exit-wave reconstruction. This technique successfully yields the genuine atomic structure of ultrathin two-dimensional CsPbBr3 halide perovskites, and a quantitative structure determination was achieved atom column by atom column using the phase information of the reconstructed exit-wave function without causing electron beam-induced sample alterations. An extraordinarily high image quality enables an unambiguous structural analysis of coexisting high temperature and low temperature phases of CsPbBr3 in single particles. On a broader level, our approach offers unprecedented opportunities to better understand halide perovskites at the atomic level as well as other radiationsensitive materials. 

In the News: LBL Highlight

[16] “Synthesis and Composition Tunable Cesium Lead Halide Nanowires through Anion-Exchange Reactions” D. Zhang, Y. Yang, Y. Yu, N. Gibson, A. Wong, S. Eaton, N. Kornienko, Q. Kong, M. Lai, Y. Bekenstein, A. P. Alivisatos, S. R. Leone, P. Yang, J. Am. Chem. Soc. 138, 7326 (2016)

Here, we demonstrate the successful synthesis of brightly emitting colloidal cesium lead halide (CsPbX3, X = Cl, Br, I) nanowires (NWs) with uniform diameters and tunable compositions. By using highly monodisperse CsPbBr3 NWs as templates, the NW composition can be independently controlled through anion-exchange reactions. CsPbX3 alloy NWs with a wide range of alloy compositions can be achieved with well-preserved morphology and crystal structure. The NWs are highly luminescent with photoluminescence quantum yields (PLQY) ranging from 20% to 80%. The bright photoluminescence can be tuned over nearly the entire visible spectrum. The high PLQYs together with charge transport measurements exemplify the efficient alloying of the anionic sublattice in a one-dimensional CsPbX3 system. The wires increased functionality in the form of fast photoresponse rates and the low defect density suggest CsPbX3 NWs as prospective materials for optoelectronic applications.

In the News: LBL Highlight

[15] “Anisotropic Phase Segregation and Migration of Pt in Nanocrystals En Route to Nanoframe Catalysts” Z. Niu, B. Becknell, Y. Yu, D. Kim, C. Chen, N. Kornienko, G. Somorjai, P. Yang, Nature Materials 15, 1188 (2016) 

Compositional heterogeneity in shaped, bimetallic nanocrystals offers additional variables to manoeuvre the functionality of the nanocrystal. However, understanding how to manipulate anisotropic elemental distributions in a nanocrystal is a great challenge in reaching higher tiers of nanocatalyst design. Here, we present the evolutionary trajectory of phase segregation in Pt–Ni rhombic dodecahedra. The anisotropic growth of a Pt-rich phase along the 111 directions at the initial growth stage results in Pt segregation to the 14 axes of a rhombic dodecahedron, forming a highly branched, Pt-rich tetradecapod structure embedded in a Ni-rich shell. With longer growth time, the Pt-rich phase selectively migrates outwards through the 14 axes to the 24 edges such that the rhombic dodecahedron becomes a Pt-rich frame enclosing a Ni-rich interior phase. The revealed anisotropic phase segregation and migration mechanism offers a radically different approach to fabrication of nanocatalysts with desired compositional distributions and performance.

In the News: LBL Highlight, Nature Energy Highlight

[14] “Growth and Photoelectrochemical Energy Conversion of Wurtzite Indium Phosphide Nanowire Arrays” N. Kornienko, N. Gibson, H. Zhang, S. W. Eaton, S. Aloni, S. Leone, P. Yang, ACS Nano, 10, 5526 (2016)

Photoelectrochemical (PEC) water splitting into hydrogen and oxygen is a promising strategy to absorb solar energy and directly convert it into a dense storage medium in the form of chemical bonds. The continual development and improvement of individual components of PEC systems is critical toward increasing the solar to fuel efficiency of prototype devices. Within this context, we describe a study on the growth of wurtzite indium phosphide (InP) nanowire (NW) arrays on silicon substrates and their subsequent implementation as light-absorbing photocathodes in PEC cells. The high onset potential (0.6 V vs the reversible hydrogen electrode) and photocurrent (18 mA/cm2) of the InP photocathodes render them as promising building blocks for high performance PEC cells. As a proof of concept for overall system integration, InP photocathodes were combined with a nanoporous bismuth vanadate (BiVO4) photoanode to generate an unassisted solar water splitting efficiency of 0.5%.

In the News: LBL Highlight

[13] “Single Nanowire Photoelectrochemistry” Y. Su, C. Liu, S. Brittman, J. Tang, A. Fu, N. Kornienko, Q. Kong, P. Yang, Nature Nanotechnology 11, 609 (2016)

Photoelectrochemistry is one of several promising approaches for the realization of efficient solar-to-fuel conversion. Recent work has shown that photoelectrodes made of semiconductor nano-/microwire arrays can have better photoelectrochemical performance than their planar counterparts because of their unique properties, such as high surface area. Although considerable research effort has focused on studying wire arrays, the inhomogeneity in the geometry, doping, defects and catalyst loading present in such arrays can obscure the link between these properties and the photoelectrochemical performance of the wires, and correlating performance with the specific properties of individual wires is difficult because of ensemble averaging. Here, we show that a single-nanowire-based photoelectrode platform can be used to reliably probe the current–voltage (I–V) characteristics of individual nanowires. We find that the photovoltage output of ensemble array samples can be limited by poorly performing individual wires, which highlights the importance of improving nanowire homogeneity within an array. Furthermore, the platform allows the flux of photogenerated electrons to be quantified as a function of the lengths and diameters of individual nanowires, and we find that the flux over the entire nanowire surface (7–30 electrons nm–2 s–1) is significantly reduced as compared with that of a planar analogue (∼1,200 electrons nm–2 s–1). Such characterization of the photogenerated carrier flux at the semiconductor/electrolyte interface is essential for designing nanowire photoelectrodes that match the activity of their loaded electrocatalysts.

In the News: LBL Highlight, Nanotech.web

[12] “TiO2/BiVO4 Heterostructure Photoanodes Based on Type II Band Allignment” J. Resarco, H. Zhang, N. Kornienko, N. Becknell, H. Lee, J. Guo, A. Briseno, P. Yang, ACS Cent. Sci. 2, 80 (2016)

Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE.

In the News: Wissehschaft, Science Daily, Popular Mechanics, IEEE

[11] “Low-Temperature Solution-Phase Growth of Silicon and Silicon Containing Alloys” J. Sun, F. Cui, C. Kiseilowski, Y. Yu, N. Kornienko, P. Yang, J. Phys. Chem. C. In Press - 2016 DOI: 10.1021/acs.jpcc.5b08289

Low-temperature synthesis of crystalline silicon and silicon-containing nanowires remains a challenge in synthetic chemistry due to the lack of sufficiently reactive Si precursors. We report that colloidal Si nanowires can be grown using tris(trimethylsilyl)silane or trisilane as the Si precursor by a Ga-mediated solution–liquid–solid (SLS) approach at temperatures of about 200 °C, which is more than 200 °C lower than that reported in the previous literature. We further demonstrate that the new Si chemistry can be adopted to incorporate Si atoms into III–V semiconductor lattices, which holds promise to produce a new Si-containing alloy semiconductor nanowire. This development represents an important step toward low-temperature fabrication of Si nanowire-based devices for broad applications.

[10] “Atomic Level Structure of P3Ni Nanoframe Electrocatalysts by In-Situ X-Ray Absorption Spectroscopy” N. Becknell, Y. Kang, C. Chen, J. Resasco, N. Kornienko, J. Guo, N. Markovic, G. Somorjai, V. Stamenkovic, P. Yang, J. Am. Chem. Soc. 37, 15817 (2015)

Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt3Ni nanoframe particles which have been proven to be an excellent electrocatalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt–Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstrates that the high ORR activity of the Pt3Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure.

[9] “Atomically Thin Two-Dimensional Organic-Inorganic Hybrid Perovskites” L. Duo, A. Wong, Y. Yu, M. Lai, N. Kornienko, S. Eaton, A. Fu, C. Bishak, J. Ma, T. Ding, N. Ginsberg, L. Wang, A. Alivisatos, P. Yang, Science, 349, 6255 (2015)

Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.

In the News: Nature Highlight, Kurzweil, Cleantechnica, EE Times, Nanowerk, LBL, AZOM, R&D Magazine, Health Medicine Network, Nanotechnology Now, e Science News, ECN Magazine, Newswise, Materials Today, CE Magazine, Science Newsline,, Science Daily, Eureka Alert, Chemistry World

[8] “Metal-Organic Frameworks for Electrocatalytic Reduction of Carbon Dioxide” N. Kornienko*, Y. Zhao*, C. Kley, C. Zhu, D. Kim, S. Lin, C. Chang, O. Yaghi, P. Yang,J. Am. Chem. Soc., 137, 14129 (2015)

A key challenge in the field of electrochemical carbon dioxide reduction is the design of catalytic materials featuring high product selectivity, stability, and a composition of earth-abundant elements. In this work, we introduce thin films of nanosized metal–organic frameworks (MOFs) as atomically defined and nanoscopic materials that function as catalysts for the efficient and selective reduction of carbon dioxide to carbon monoxide in aqueous electrolytes. Detailed examination of a cobalt–porphyrin MOF, Al2(OH)2TCPP-Co (TCPP-H2 = 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzoate) revealed a selectivity for CO production in excess of 76% and stability over 7 h with a per-site turnover number (TON) of 1400. In situ spectroelectrochemical measurements provided insights into the cobalt oxidation state during the course of reaction and showed that the majority of catalytic centers in this MOF are redox-accessible where Co(II) is reduced to Co(I) during catalysis.

In the News: ALS Highlight

[7] “Covalent Organic Frameworks Comprising Cobalt Porphyrins for Catalytic CO2 Reduction in Water” S. Lin*, C. Dierks*, Y. Zhang*, N. Kornienko, E. Nichols, Y. Zhao, A. Paris, D. Kim, P. Yang, O. Yaghi, C. Chang, Science, 349, 1208 (2015)

Conversion of carbon dioxide (CO2) to carbon monoxide (CO) and other value-added carbon products is an important challenge for clean energy research. Here we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000, with initial turnover frequency of 9400 hour−1) at pH 7 with an overpotential of –0.55 volts, equivalent to a 26-fold improvement in activity compared with the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.

In the News: LBL Highlight, Kurzweil, Newswise, Materials Today, Smithsonian Magazine, e Science News, Eureka Alert,, Conservation Magazine,, Innovations Reports, ECN Magazine, Nanowerk, Lab Manager

[6] “Operando Spectroscopic Analysis of an Amorphous Cobalt Sulfide Electrocatalyst” N. Kornienko, J. Resasco, N. Becknell, C. Jiang, Y. Liu, K. Nie, X. Sun, J. Guo, S. Leone, P. Yang, J. Am. Chem. Soc., 137, 7448 (2015)

The generation of chemical fuel in the form of molecular H2 via the electrolysis of water is regarded to be a promising approach to convert incident solar power into an energy storage medium. Highly efficient and cost-effective catalysts are required to make such an approach practical on a large scale. Recently, a number of amorphous hydrogen evolution reaction (HER) catalysts have emerged that show promise in terms of scalability and reactivity, yet remain poorly understood. In this work, we utilize Raman spectroscopy and X-ray absorption spectroscopy (XAS) as a tool to elucidate the structure and function of an amorphous cobalt sulfide (CoSx) catalyst. Ex situ measurements reveal that the as-deposited CoSx catalyst is composed of small clusters in which the cobalt is surrounded by both sulfur and oxygen. Operando experiments, performed while the CoSx is catalyzing the HER, yield a molecular model in which cobalt is in an octahedral CoS2-like state where the cobalt center is predominantly surrounded by a first shell of sulfur atoms, which, in turn, are preferentially exposed to electrolyte relative to bulk CoS2. We surmise that these CoS2-like clusters form under cathodic polarization and expose a high density of catalytically active sulfur sites for the HER.

[5] “Solution Phase Synthesis of Indium Gallium Phosphide Alloy Nanowires” N. Kornienko, D. Whitmore, Y. Yu, S. Leone and P. Yang, ACS Nano, 9, 3951 (2015)

The tunable physical and electronic structure of III–V semiconductor alloys renders them uniquely useful for a variety of applications, including biological imaging, transistors, and solar energy conversion. However, their fabrication typically requires complex gas phase instrumentation or growth from high-temperature melts, which consequently limits their prospects for widespread implementation. Furthermore, the need for lattice matched growth substrates in many cases confines the composition of the materials to a narrow range that can be epitaxially grown. In this work, we present a solution phase synthesis for indium gallium phosphide (InxGa1–xP) alloy nanowires, whose indium/gallium ratio, and consequently, physical and electronic structure, can be tuned across the entire x = 0 to x = 1 composition range. We demonstrate the evolution of structural and optical properties of the nanowires, notably the direct to indirect band gap transition, as the composition is varied from InP to GaP. Our scalable, low-temperature synthesis affords compositional, structural, and electronic tunability and can provide a route for realization of broader InxGa1–xP applications.

[4] “Mesoscopic Constructs of Ordered and Oriented Metal-Organic Frameworks on Plasmonic Silver Nanocrystals” Y. Zhao*, N. Kornienko*, Z. Liu,C. Zhu, S. Asahina,  T. Kuo, W. Bao, C. Xie, O. Terasaki, P. Yang, O. Yaghi, J. Am. Chem. Soc., 137, 2199, 2015

We enclose octahedral silver nanocrystals (Ag NCs) in metal–organic frameworks (MOFs) to make mesoscopic constructs Oh-nano-Ag⊂MOF in which the interface between the Ag and the MOF is pristine and the MOF is ordered (crystalline) and oriented on the Ag NCs. This is achieved by atomic layer deposition of aluminum oxide on Ag NCs and addition of a tetra-topic porphyrin-based linker, 4,4′,4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrabenzoic acid (H4TCPP), to react with alumina and make MOF [Al2(OH)2TCPP] enclosures around Ag NCs. Alumina thickness is precisely controlled from 0.1 to 3 nm, thus allowing control of the MOF thickness from 10 to 50 nm. Electron microscopy and grazing angle X-ray diffraction confirm the order and orientation of the MOF by virtue of the porphyrin units being perpendicular to the planes of the Ag. We use surface-enhanced Raman spectroscopy to directly track the metalation process on the porphyrin and map the distribution of the metalated and unmetalated linkers on a single-nanoparticle level.

[3]"Visible Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene Isoquinoline Complex”, V Thoi*, N. Kornienko*, C Margarit, P. Yang and C. Chang, J. Am. Chem. Soc., 135, 14413 (2013).

The solar-driven reduction of carbon dioxide to value-added chemical fuels is a longstanding challenge in the fields of catalysis, energy science, and green chemistry. In order to develop effective CO2 fixation, several key considerations must be balanced, including (1) catalyst selectivity for promoting CO2 reduction over competing hydrogen generation from proton reduction, (2) visible-light harvesting that matches the solar spectrum, and (3) the use of cheap and earth-abundant catalytic components. In this report, we present the synthesis and characterization of a new family of earth-abundant nickel complexes supported by N-heterocyclic carbene–amine ligands that exhibit high selectivity and activity for the electrocatalytic and photocatalytic conversion of CO2 to CO. Systematic changes in the carbene and amine donors of the ligand have been surveyed, and [Ni(Prbimiq1)]2+ (1c, where Prbimiq1 = bis(3-(imidazolyl)isoquinolinyl)propane) emerges as a catalyst for electrochemical reduction of CO2 with the lowest cathodic onset potential (Ecat = −1.2 V vs SCE). Using this earth-abundant catalyst with Ir(ppy)3 (where ppy = 2-phenylpyridine) and an electron donor, we have developed a visible-light photoredox system for the catalytic conversion of CO2 to CO that proceeds with high selectivity and activity and achieves turnover numbers and turnover frequencies reaching 98,000 and 3.9 s–1, respectively. Further studies reveal that the overall efficiency of this solar-to-fuel cycle may be limited by the formation of the active Ni catalyst and/or the chemical reduction of CO2 to CO at the reduced nickel center and provide a starting point for improved photoredox systems for sustainable carbon-neutral energy conversion.

[2] "Reflectivity Enhanced Two-Dimensional Dielectric Particle Array Monolayer Diffraction", A. Tikhonov, N. Kornienko, J. Zhang, L. Wang and S.A. Asher, J. Nanophoton., 6, 063509 (2012).

Very high diffraction efficiencies (>80%>80%) were observed from two-dimensional (2-D) photonic crystals made of monolayers of ∼490 nm∼490 nm diameter dielectric polystyrene spheres arranged in a 2-D hexagonal lattice on top of a liquid mercury surface. These almost close packed 2-D polystyrene particle arrays were prepared by a self-assembly spreading method that utilizes solvent evaporation from the mercury surface. Two-dimensional arrays transferred onto a dielectric glass substrate placed on top of metal mirrors show diffraction efficiencies of over 30%, which is 6- to 8-fold larger than those of the same 2-D monolayers in the absence of mirrors. A simple single particle scattering model with refraction explains the high diffraction efficiencies in terms of reflection of the high intensity forward diffraction.

[1] "2-D Array Photonic Crystal Sensing Motif”, J. Zhang, L. Wang, J. Luo, A. Tikhonov, N. Kornienko, and S.A. Asher, J. Am. Chem. Soc., 133, 9152 (2011).

We have developed the first high-diffraction-efficiency two-dimensional (2-D) photonic crystals for molecular recognition and chemical sensing applications. We prepared close-packed 2-D polystyrene particle arrays by self-assembly of spreading particle monolayers on mercury surfaces. The 2-D particle arrays amazingly diffract 80% of the incident light. When a 2-D array was transferred onto a hydrogel thin film showing a hydrogel volume change in response to a specific analyte, the array spacing was altered, shifting the 2-D array diffraction wavelength. These 2-D array photonic crystals exhibit ultrahigh diffraction efficiencies that enable them to be used for visual determination of analyte concentrations.