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.

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.

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.

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.

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.

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.

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.

Operando Investigation of Ag-Decorated Cu O Nanocube Catalysts with Enhanced CO Electroreduction toward Liquid Products.

Direct conversion of carbon dioxide into multicarbon liquid fuels by the CO electrochemical reduction reaction (CO RR) can contribute to the decarbonization of the global economy. Here, well-defined Cu O nanocubes (NCs, 35 nm) uniformly covered with Ag nanoparticles (5 nm) were synthesized. When compared to bare Cu O NCs, the catalyst with 5 at % Ag on Cu O NCs displayed a two-fold increase in the Faradaic efficiency for C liquid products (30 % at -1.

Linking the evolution of catalytic properties and structural changes in copper-zinc nanocatalysts using EXAFS and neural-networks.

Understanding the evolution of unique structural motifs in bimetallic catalysts under reaction conditions, and linking them to the observed catalytic properties is necessary for the rational design of the next generation of catalytic materials. Extended X-ray absorption fine structure (EXAFS) spectroscopy is a premier experimental method to address this issue, providing the possibility to track the changes in the structure of working catalysts. Unfortunately, the intrinsic heterogeneity and enhanced disorder characteristic of catalytic materials experiencing structural transformations under reaction conditions, as well as the low signal-to-noise ratio that is common for EXAFS spectra hinder the application of conventional data analysis approaches.

Operando Insight into the Correlation between the Structure and Composition of CuZn Nanoparticles and Their Selectivity for the Electrochemical CO Reduction.

Bimetallic CuZn catalysts have been recently proposed as alternatives in order to achieve selectivity control during the electrochemical reduction of CO (CORR). However, fundamental understanding of the underlying reaction mechanism and parameters determining the CORR performance is still missing. In this study, we have employed size-controlled (∼5 nm) CuZn nanoparticles (NPs) supported on carbon to investigate the correlation between their structure and composition and catalytic performance.

Electrochemical Real-Time Mass Spectrometry (EC-RTMS): Monitoring Electrochemical Reaction Products in Real Time.

Methods that provide real-time information are essential to resolve transients occurring at dynamic interfaces. Now a powerful method is presented that enables the time- and potential-resolved characterization of liquid and gaseous products of electrochemical reactions shortly after their formation. To demonstrate its extraordinary potential, the electrochemical real time mass spectrometry (EC-RTMS) approach is used to determine the products of the CO reduction reaction (CO RR) during potential step or sweep experiments on pristine and in situ anodized copper.