Interfacial solvation pre-organizes the transition state of the oxygen evolution reaction.

The sluggish kinetics of the oxygen evolution reaction are an energetic bottleneck for green hydrogen production via water electrolysis. The reaction proceeds over a surface that undergoes (frustrated) phase transitions to accommodate bias-dependent excess charge. Here we perform Arrhenius analysis of common catalysts and correlate the activation energy and pre-exponential factor with the oxide's structural adaptation via operando X-ray absorption spectroscopy and high-energy X-ray diffraction.

Revealing catalyst restructuring and composition during nitrate electroreduction through correlated operando microscopy and spectroscopy.

Electrocatalysts alter their structure and composition during reaction, which can in turn create new active/selective phases. Identifying these changes is crucial for determining how morphology controls catalytic properties but the mechanisms by which operating conditions shape the catalyst's working state are not yet fully understood. In this study, we show using correlated operando microscopy and spectroscopy that as well-defined CuO cubes evolve under electrochemical nitrate reduction reaction conditions, distinct catalyst motifs are formed depending on the applied potential and the chemical environment.

Adsorbate Configurations in Ni Single-Atom Catalysts during CO_{2} Electrocatalytic Reduction Unveiled by Operando XAS, XES, and Machine Learning.

Nickel and nitrogen co-doped carbon (Ni-N-C) catalysts are attracting attention due to their exceptionally high performance in the electrocatalytic reduction of CO_{2}(CO_{2}RR) to CO. However, the direct experimental insight into the working mechanism of these catalysts is missing, hindering our fundamental understanding and their further improvement. This work sheds light on the nature of adsorbates forming under CO_{2}RR at singly dispersed Ni sites.

Reactivity and Stability of Reduced Ir-Weight TiO-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes.

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO-supported Ir@IrO(OH) core-shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO-supported Ir@IrO(OH) core-shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A g at 1.

Reversible metal cluster formation on Nitrogen-doped carbon controlling electrocatalyst particle size with subnanometer accuracy.

Copper and nitrogen co-doped carbon catalysts exhibit a remarkable behavior during the electrocatalytic CO reduction (CORR), namely, the formation of metal nanoparticles from Cu single atoms, and their subsequent reversible redispersion. Here we show that the switchable nature of these species holds the key for the on-demand control over the distribution of CORR products, a lack of which has thus far hindered the wide-spread practical adoption of CORR. By intermitting pulses of a working cathodic potential with pulses of anodic potential, we were able to achieve a controlled fragmentation of the Cu particles and partial regeneration of single atom sites.

Synergizing FeO Nanoparticles on Single Atom Fe-N-C for Nitrate Reduction to Ammonia at Industrial Current Densities.

The electrochemical reduction of nitrates (NO ) enables a pathway for the carbon neutral synthesis of ammonia (NH), via the nitrate reduction reaction (NORR), which has been demonstrated at high selectivity. However, to make NH synthesis cost-competitive with current technologies, high NH partial current densities (j) must be achieved to reduce the levelized cost of NH. Here, the high NORR activity of Fe-based materials is leveraged to synthesize a novel active particle-active support system with FeO nanoparticles supported on atomically dispersed Fe-N-C.

Electrocatalytic Nitrate and Nitrite Reduction toward Ammonia Using CuO Nanocubes: Active Species and Reaction Mechanisms.

The electrochemical reduction of nitrate (NO) and nitrite (NO) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH). Copper-based materials are promising electrocatalysts for NO conversion to NH. However, the underlying reaction mechanisms and the role of different Cu species during the catalytic process are still poorly understood.

Enhanced Methanol Synthesis from CO Hydrogenation Achieved by Tuning the Cu-ZnO Interaction in ZnO/CuO Nanocube Catalysts Supported on ZrO and SiO.

The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation.

Role of Fe decoration on the oxygen evolving state of CoO nanocatalysts.

The production of green hydrogen through alkaline water electrolysis is the key technology for the future carbon-neutral industry. Nanocrystalline CoO catalysts are highly promising electrocatalysts for the oxygen evolution reaction and their activity strongly benefits from Fe surface decoration. However, limited knowledge of decisive catalyst motifs at the atomic level during oxygen evolution prevents their knowledge-driven optimization.

insights into correlating CO coverage and Cu-Au alloying with the selectivity of Au NP-decorated CuO nanocubes during the electrocatalytic CO reduction.

Electrochemical reduction of CO (CORR) is an attractive technology to reintegrate the anthropogenic CO back into the carbon cycle driven by a suitable catalyst. This study employs highly efficient multi-carbon (C) producing CuO nanocubes (NCs) decorated with CO-selective Au nanoparticles (NPs) to investigate the correlation between a high CO surface concentration microenvironment and the catalytic performance. Structure, morphology and near-surface composition are studied X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy, high-energy X-ray diffraction as well as quasi X-ray photoelectron spectroscopy.

Dynamic behaviour of platinum and copper dopants in gold nanoclusters supported on ceria catalysts.

Understanding the behaviour of active catalyst sites at the atomic level is crucial for optimizing catalytic performance. Here, the evolution of Pt and Cu dopants in Au clusters on CeO supports is investigated in the water-gas shift (WGS) reaction, using operando XAFS and DRIFTS. Different behaviour is observed for the Cu and Pt dopants during the pretreatment and reaction.

Reversible Structural Evolution of Metal-Nitrogen-Doped Carbon Catalysts During CO Electroreduction: An Operando X-ray Absorption Spectroscopy Study.

Electrochemical CO reduction (CO RR) is a rising technology, aiming to reduce the energy sector dependence on fossil fuels and to produce carbon-neutral raw materials. Metal-nitrogen-doped carbons (M-N-C) are emerging, cost-effective catalysts for this reaction; however, their long-term stability is a major issue. To overcome this, understanding their structural evolution is crucial, requiring systematic in-depth operando studies.

Spatially and Chemically Resolved Visualization of Fe Incorporation into NiO Octahedra during the Oxygen Evolution Reaction.

The activity of Ni (hydr)oxides for the electrochemical evolution of oxygen (OER), a key component of the overall water splitting reaction, is known to be greatly enhanced by the incorporation of Fe. However, a complete understanding of the role of cationic Fe species and the nature of the catalyst surface under reaction conditions remains unclear. Here, using a combination of electrochemical cell and conventional transmission electron microscopy, we show how the surface of NiO electrocatalysts, with initially well-defined surface facets, restructures under applied potential and forms an active NiFe layered double (oxy)hydroxide (NiFe-LDH) when Fe ions are present in the electrolyte.

Tracking the Evolution of Single-Atom Catalysts for the CO Electrocatalytic Reduction Using Operando X-ray Absorption Spectroscopy and Machine Learning.

Transition metal-nitrogen-doped carbons (TMNCs) are a promising class of catalysts for the CO electrochemical reduction reaction. In particular, high CO-to-CO conversion activities and selectivities were demonstrated for Ni-based TMNCs. Nonetheless, open questions remain about the nature, stability, and evolution of the Ni active sites during the reaction.

Deciphering the Structural and Chemical Transformations of Oxide Catalysts during Oxygen Evolution Reaction Using Quick X-ray Absorption Spectroscopy and Machine Learning.

Bimetallic transition-metal oxides, such as spinel-like CoFeO materials, are known as attractive catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. Nonetheless, unveiling the real active species and active states in these catalysts remains a challenge. The coexistence of metal ions in different chemical states and in different chemical environments, including disordered X-ray amorphous phases that all evolve under reaction conditions, hinders the application of common operando techniques.

Shape-Dependent CO Hydrogenation to Methanol over CuO Nanocubes Supported on ZnO.

The hydrogenation of CO to methanol over Cu/ZnO-based catalysts is highly sensitive to the surface composition and catalyst structure. Thus, its optimization requires a deep understanding of the influence of the pre-catalyst structure on its evolution under realistic reaction conditions, including the formation and stabilization of the most active sites. Here, the role of the pre-catalyst shape (cubic vs spherical) in the activity and selectivity of ZnO-supported Cu nanoparticles was investigated during methanol synthesis.

Role of Nanoscale Inhomogeneities in CoFeO Catalysts during the Oxygen Evolution Reaction.

Spinel-type catalysts are promising anode materials for the alkaline oxygen evolution reaction (OER), exhibiting low overpotentials and providing long-term stability. In this study, we compared two structurally equal CoFeO spinels with nominally identical stoichiometry and substantially different OER activities. In particular, one of the samples, characterized by a metastable precatalyst state, was found to quickly achieve its steady-state optimum operation, while the other, which was initially closer to the ideal crystallographic spinel structure, never reached such a state and required 168 mV higher potential to achieve 1 mA/cm.

Tracking heterogeneous structural motifs and the redox behaviour of copper-zinc nanocatalysts for the electrocatalytic CO reduction using operando time resolved spectroscopy and machine learning.

Copper-based catalysts are established catalytic systems for the electrocatalytic CO reduction reaction (CORR), where the greenhouse gas CO is converted into valuable industrial chemicals, such as energy-dense C products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions, is needed to expedite the economic viability of the CORR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for the CORR.

Multi-scale microscopy study of 3D morphology and structure of MoNi/MoO@Ni electrocatalytic systems for fast water dissociation.

The 3D morphology of hierarchically structured electrocatalytic systems is determined based on multi-scale X-ray computed tomography (XCT), and the crystalline structure of electrocatalyst nanoparticles is characterized using transmission electron microscopy (TEM), supported by X-ray diffraction (XRD) and spatially resolved near-edge X-ray absorption fine structure (NEXAFS) studies. The high electrocatalytic efficiency for hydrogen evolution reaction (HER) of a novel transition-metal-based material system - MoNi electrocatalysts anchored on MoO cuboids aligned on Ni foam (MoNi/MoO@Ni) - is based on advantageous crystalline structures and chemical bonding. High-resolution TEM images and selected-area electron diffraction patterns are used to determine the crystalline structures of MoO and MoNi.

Efficient Electrochemical Nitrate Reduction to Ammonia with Copper-Supported Rhodium Cluster and Single-Atom Catalysts.

The electrochemical nitrate reduction reaction (NITRR) provides a promising solution for restoring the imbalance in the global nitrogen cycle while enabling a sustainable and decentralized route to source ammonia. Here, we demonstrate a novel electrocatalyst for NITRR consisting of Rh clusters and single-atoms dispersed onto Cu nanowires (NWs), which delivers a partial current density of 162 mA cm for NH production and a Faradaic efficiency (FE) of 93 % at -0.2 V vs.

Covalent Organic Framework (COF) Derived Ni-N-C Catalysts for Electrochemical CO Reduction: Unraveling Fundamental Kinetic and Structural Parameters of the Active Sites.

Electrochemical CO reduction is a potential approach to convert CO into valuable chemicals using electricity as feedstock. Abundant and affordable catalyst materials are needed to upscale this process in a sustainable manner. Nickel-nitrogen-doped carbon (Ni-N-C) is an efficient catalyst for CO reduction to CO, and the single-site Ni-N motif is believed to be the active site.

Creation of Exclusive Artificial Cluster Defects by Selective Metal Removal in the (Zn, Zr) Mixed-Metal UiO-66.

The differentiation between missing linker defects and missing cluster defects in MOFs is difficult, thereby limiting the ability to correlate materials properties to a specific type of defects. Herein, we present a novel and easy synthesis strategy for the creation of solely "missing cluster defects" by preparing mixed-metal (Zn, Zr)-UiO-66 followed by a gentle acid wash to remove the Zn nodes. The resulting material has the UiO-66 structure, typical for well-defined missing cluster defects.

Selectivity Control of Cu Nanocrystals in a Gas-Fed Flow Cell through CO Pulsed Electroreduction.

In this study, we have taken advantage of a pulsed CO electroreduction reaction (CORR) approach to tune the product distribution at industrially relevant current densities in a gas-fed flow cell. We compared the CORR selectivity of Cu catalysts subjected to either potentiostatic conditions (fixed applied potential of -0.7 V) or pulsed electrolysis conditions (1 s pulses at oxidative potentials ranging from = 0.