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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.

Electrocatalytic formation of C–N bonds was achieved through the electrolysis of CO2 and NH3 over Cu catalysts. A combined analytical and spectroscopic approach gave insights into the reaction mechanism leading to formamide and acetamide products.

Summary 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.

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.

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.

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.

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.

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.

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.

Doping/decorating of graphene or reduced graphene oxide (rGO) with heteroatoms provides a promising route for the development of electrocatalysts which will be 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/decorated 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 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 versus the reversible hydrogen electrode with a Tafel slope of 43 mV dec–1 and possesses high durability, as evidenced through 10 h of stability testing. Electrochemical analyses suggest the importance of Fe and its possible role as an active site for OER. Overall, this work represents a simple approach toward the development of an earth-abundant, eco-friendly, and highly active OER electrocatalyst for various applications such as solar fuel production, rechargeable metal–air batteries, and microbial electrosynthesis.

Electrochemical conversion of abundant feedstocks to fuels and value-added chemicals is rapidly gaining significance as a promising method to harness renewable electricity. To this end, research group develops heterogeneous catalysts (e.g. nanomaterials, MOFs) geared for the reduction of CO2 and oxidation of biomass platforms to fuels and value-added chemicals. Further, we establish strategies in emergent areas of electrocatalysis such as electrochemically forming and cleaving C-N bonds. Because the design of new catalytic systems is inherently linked to a precise understanding of how these reactions proceed on heterogeneous surfaces, we put considerable efforts in developing methodology for operando probing of these systems with vibrational spectroscopy. In all, I show how using these experiments provides key mechanistic information on surface reaction mechanisms that enhance our understanding of functional interfaces and how the research provides avenues for future materials design within the context of renewable energy electrocatalysis.

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.

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, Ni-MOF-74D, is evaluated vs. the nominally defect-free Ni-MOF-74 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 Ni-MOF-74D 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 Ni-MOF-74 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., 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.

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.

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 furfural alcohol or 2-methylfuran.

Enzymes use adaptive catalytic pocket to accelerate catalysis. Recently published in Nature Catalysis, Zhong and coworkers have translated this functionality into a MOF with a Cu-Ni active site in which the Cu-Ni distance changes to stabilize intermediates along the CO2 to CH4 pathway and give rise to exceptional catalytic selectivity.

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 node. 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. The strategy put forth to rationally design coordinatively-unsaturated electrocatalytic sites and the methodology put forth in investigating their behavior stand to bolster the understanding and growth of the field.

International audience; 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.

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase (FDH) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO 2 reduction and report an in-depth study of the resulting enzyme–material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal-oxide electrodes and reveals the reversible and selective reduction of CO 2 to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR-IR) spectroscopy confirm a high binding affinity for FDH to the TiO 2 surface. Adsorption of FDH on dye-sensitized TiO 2 allows for visible-light-driven CO 2 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 the selective photoreduction of aqueous CO 2 to formate. authorsversion published

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 begun to translate the methodology and concepts from water/CO2 electrolysis to biomass valorization to 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.

Electrocatalytic reduction of carbon dioxide (CO2R) to fuels and chemicals is a pressing scientificand engineering challenge that is, in part, hampered by a lack of understanding of the surface reactionmechanism, even for relatively simple systems. While many efforts have been dedicated to promoting CO2Ron catalytic surfaces by tuning composition, morphology, and defects, the role of the reaction environmentaround the active site, and how this can be leveraged to modulate CO2R, is less clear. To this end, wefocused on a model CO2R catalyst, Ag nanoparticles, and carried out a combined electrocatalytic andoperando Raman spectroscopic investigation of CO2R on their surfaces. Bare Ag and chemically modifiedAg nanoparticles were investigated to understand how the surface reaction environment dictatesintermediate binding and catalytic efficiency en route to CO generation. The results revealed that theprimary 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 COatopconfiguration on their surfaces, whereas porous zeolitic-imidazolate framework-coated Ag was observedto bind both CObridge and COatop. Further, another function of the Ag surface modifications is to dictate thetype of Ag surface sites which form Ag-C bonds with CO2R intermediates. Through analysis of the ofelectrochemical and spectroscopic data, we deduce which key aspects of CO2R on Ag surface render aCO2R system efficient and show how surface chemistry dictates diverging CO2R surface reactionmechanisms. The insights gained here are important as they provide the community with a greaterunderstanding of heterogeneous CO2R and can be further translated to a number of catalytic systems.

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. By 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. This work sheds light on the mechanisms of G. sulfurreducens biofilm growth and suggests the possible existence of a nonheme, iron-involving EET process in cathodic mode.

Natural photosynthesis stores sunlight in chemical energy carriers, but it has not evolved for the efficient synthesis of fuels, such as H2. Semi-artificial photosynthesis combines the strengths of natural photosynthesis with synthetic chemistry and materials science to develop model systems that overcome nature’s limitations, such as low-yielding metabolic pathways and non-complementary light absorption by photosystems I and II. Here, we report a bias-free semi-artificial tandem platform that wires photosystem II to hydrogenase for overall water splitting. This photoelectrochemical cell integrated the red and blue light-absorber photosystem II with a green light-absorbing diketopyrrolopyrrole dye-sensitized TiO2 photoanode, and so enabled complementary panchromatic solar light absorption. Effective electronic communication at the enzyme–material interface was engineered using an osmium-complex-modified redox polymer on a hierarchically structured TiO2. This system provides a design protocol for bias-free semi-artificial Z schemes in vitro and provides an extended toolbox of biotic and abiotic components to re-engineer photosynthetic pathways.

© 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. Hydrogenases (H2ases) are benchmark electrocatalysts for H2 production, both in biology and (photo)catalysis in vitro. We report the tailoring of a p-type Si photocathode for optimal loading and wiring of H2ase through 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 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.

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 necessarily 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 possibility to exploit the O2 reduction reaction to inhibit deactivation, rather than catalysis, offering a strategy to stabilise photocatalysts that suffer from similar degradation reactions.

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 (

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 photovoltaic devices.

Photosynthetic biohybrid systems (PBSs) combine the strengths of inorganic materials and biological catalysts by 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 sustainable living here on earth and beyond.

The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging clean energy technology., The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging clean energy 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 1 M KOH. In contrast to the case in 1 M KOH, NiOOH formation is suppressed, and consequently HMF oxidation is sluggish in 10 mM KOH, even at highly oxidizing 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 the catalysts' physical and electronic structure. The insights extracted are expected to pave the way for a deepened understanding of a wide array of electrochemical systems such as for organic transformations and CO2 fixation.

The paper analyses the history of missionary work of Russian Orthodox church in Mongolia. The research is centered around the public work of Milij Chefranov, senior priest of Urgin church. The author briefly outlines all the major elements of his work that lead to the low Russian Orthodox mission efficiency in the neighbor country.

The electrochemical oxidation of biomass platforms such as 5-hydroxymethylfurfural (HMF) to value-added chemicals is an emerging clean energy 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 1 M KOH. In contrast to the case in 1 M KOH, NiOOH formation is suppressed, and consequently HMF oxidation is sluggish in 10 mM KOH, even at highly oxidizing 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 the catalysts' physical and electronic structure. The insights extracted are expected to pave the way for a deepened understanding of a wide array of electrochemical systems such as for organic transformations and CO2 fixation.

The development of electrocatalysts for the oxygen evolution reaction (OER) is one of the principal challenges in the area of renewable energy research., 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 and NiFe2F8(H2O)2, and amorphous oxyfluorides, NiFe2F4.4O1.8 and CoFe2F6.6O0.7, feature excellent activity (overpotential for 10 mA cm–2 as low as 270 mV) and stability (extended performance for >250 hours with ∼40 mV activity loss) 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, which carried out overall water splitting at 1.65 V at 10 mA cm–2.

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.

[Image: see text] Enzymes are the essential catalytic components of biology and adsorbing redox-active enzymes on electrode surfaces enables the direct probing of their function. Through standard electrochemical measurements, catalytic activity, reversibility and stability, potentials of redox-active cofactors, and interfacial electron transfer rates can be readily measured. Mechanistic investigations on the high electrocatalytic rates and selectivity of enzymes may yield inspiration for the design of synthetic molecular and heterogeneous electrocatalysts. Electrochemical investigations of enzymes also aid in our understanding of their activity within their biological environment and why they evolved in their present structure and function. However, the conventional array of electrochemical techniques (e.g., voltammetry and chronoamperometry) alone offers a limited picture of the enzyme–electrode interface. How many enzymes are loaded onto an electrode? In which orientation(s) are they bound? What fraction is active, and are single or multilayers formed? Does this static picture change over time, applied voltage, or chemical environment? How does charge transfer through various intraprotein cofactors contribute to the overall performance and catalytic bias? What is the distribution of individual enzyme activities within an ensemble of active protein films? These are central questions for the understanding of the enzyme–electrode interface, and a multidisciplinary approach is required to deliver insightful answers. 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 permits the simultaneous determination of reaction kinetics and 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 provides insights into active site states and the 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 toward attaining a complete mechanistic picture of the enzyme–electrode interface.

Electrochemical conversion of abundant feedstocks to fuels and value-added chemicals is rapidly gaining significance as a promising method to harness renewable electricity. Specific reactions within this context that my research group is focused on are the reduction of CO2 and oxidation of waste biomass. Because the design of new catalytic systems is inherently linked to a precise understanding of how these reactions proceed on heterogeneous surfaces, we put considerable efforts in developing methodology for opernado probing with Raman spectroscopy CO2 reduction and biomass valorization. This talk will detail our efforts in the design, electrochemical characterization, and spectroscopic investigation of 1) Composite systems of metallic nanoparticles decorated with functional organic ligands with steer CO2 reduction reactions down a select pathway on their surface 2) Tandem CO2 catalysis at the material-Metal Organic Framework (MOF) interface 3) Electrochemical oxidationof 5-hydroxymethylfurfural (HMF) on gold and transition metal oxide surface In all, I show how using opernado Raman spectroscopy provides the mechanistic information on surface reaction mechanisms that enhance our understanding of functional hybrid interfaces and provides avenues for future materials design within the context of electrosynthesis of fuels and chemicals. Figure 1

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〉 and 〈200〉 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.

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/cm(2)) 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%.

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.

Electrocatalysts enable many energy conversion and storage technologies. Tuning the electronic structure of electrocatalytic transition metal oxides and complexes by introducing substitute metals—which possess a different electronegativity than the parent metals—presents a rational strategy for enhancing performance. Kuznetsov et al. show a unifying concept regarding how the inductive effects of substitute metals alter the molecular orbital structure of transition metal oxides and complexes. Such tuning leads to increased battery capacity and higher catalytic activity.