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Catalysts for chemical and electrochemical reactions underpin many aspects of modern technology and industry, from energy storage and conversion to toxic emissions abatement to chemical and materials synthesis. This role necessitates the design of highly active, stable, yet earth-abundant heterogeneous catalysts. In this Review, we present the perovskite oxide family as a basis for developing such catalysts for (electro)chemical conversions spanning carbon, nitrogen, and oxygen chemistries. A framework for rationalizing activity trends and guiding perovskite oxide catalyst design is described, followed by illustrations of how a robust understanding of perovskite electronic structure provides fundamental insights into activity, stability, and mechanism in oxygen electrocatalysis. We conclude by outlining how these insights open experimental and computational opportunities to expand the compositional and chemical reaction space for next-generation perovskite catalysts.

Medium- and high-entropy alloys (M/HEAs) mix several principal elements with near-equiatomic composition and represent a model-shift strategy for designing previously unknown materials in metallurgy, catalysis and other fields. One of the core hypotheses of M/HEAs is lattice distortion, which has been investigated by different numerical and experimental techniques. However, determining the three-dimensional (3D) lattice distortion in M/HEAs remains a challenge. Moreover, the presumed random elemental mixing in M/HEAs has been questioned by X-ray and neutron studies, atomistic simulations, energy dispersive spectroscopy and electron diffraction, which suggest the existence of local chemical order in M/HEAs. However, direct experimental observation of the 3D local chemical order has been difficult because energy dispersive spectroscopy integrates the composition of atomic columns along the zone axes and diffuse electron reflections may originate from planar defects instead of local chemical order. Here, in this work, we determine the 3D atomic positions of M/HEA nanoparticles using atomic electron tomography and quantitatively characterize the local lattice distortion, strain tensor, twin boundaries, dislocation cores and chemical short-range order (CSRO). We find that the high-entropy alloys have larger local lattice distortion and more heterogeneous strain than the medium-entropy alloys and that strain is correlated to CSRO. We also observe CSRO-mediated twinning in the medium-entropy alloys, that is, twinning occurs in energetically unfavoured CSRO regions but not in energetically favoured CSRO ones, which represents, to our knowledge, the first experimental observation of correlating local chemical order with structural defects in any material. We expect that this work will not only expand our fundamental understanding of this important class of materials but also provide the foundation for tailoring M/HEA properties through engineering lattice distortion and local chemical order.

Electro-Fenton processes aim at producing oxidizing radicals with fewer added chemicals and residues but are still unable to completely eliminate both. This study demonstrates that a reagent-free electro-Fenton process that runs solely on oxygen and electricity can be achieved by sequential dual-cathode electrocatalysis. H₂O₂ is produced on an electrodeposited PEDOT on carbon cloth (PEDOT/CC) cathode and subsequently converted to hydroxyl radicals on a stainless-steel–mesh cathode. The dual-cathode system demonstrates efficient decolorization and total organic carbon (TOC) removal toward organic dyes at optimized cathodic potentials of −0.9 V for PEDOT/CC and −0.8 V for the stainless-steel mesh. The sequential dual-cathode process also displays high reusability, no iron leaching, high removal efficiency using air instead of oxygen, and low installation and operation costs. This work demonstrates a preeminent and commercially viable example of pollution control rendered by the “catalysis instead of chemical reagent” philosophy of green chemistry.

The enzyme nitrogenase inspires the development of novel photocatalytic and electrocatalytic systems that can drive nitrogen reduction with water under similar low‐temperature and low‐pressure conditions. While photocatalytic and electrocatalytic N 2 fixation are emerging as hot new areas of fundamental and applied research, serious concerns exist regarding the accuracy of current methods used for ammonia detection and quantification. In most studies, the ammonia yields are low and little consideration is given to the effect of interferants on NH 3 quantification. As a result, NH 3 yields reported in many works may be exaggerated and erroneous. Herein, the advantages and limitations of the various methods commonly used for NH 3 quantification in solution (Nessler's reagent method, indophenol blue method, and ion chromatography method) are systematically explored, placing particular emphasis on the effect of interferants on each quantification method. Based on the data presented, guidelines are suggested for responsible quantification of ammonia in photocatalysis and electrocatalysis.

Structure–activity relationships built on descriptors of bulk and bulk-terminated surfaces are the basis for the rational design of electrocatalysts. However, electrochemically driven surface transformations complicate the identification of such descriptors. In this work, we demonstrate how the as-prepared surface composition of (001)-terminated LaNiO3 epitaxial thin films dictates the surface transformation and the electrocatalytic activity for the oxygen evolution reaction. Specifically, the Ni termination (in the as-prepared state) is considerably more active than the La termination, with overpotential differences of up to 150 mV. A combined electrochemical, spectroscopic and density-functional theory investigation suggests that this activity trend originates from a thermodynamically stable, disordered NiO2 surface layer that forms during the operation of Ni-terminated surfaces, which is kinetically inaccessible when starting with a La termination. Our work thus demonstrates the tunability of surface transformation pathways by modifying a single atomic layer at the surface and that active surface phases only develop for select as-synthesized surface terminations.

The construction of strong interactions and synergistic effects between small metal clusters and supports offers a great opportunity to achieve high‐performance and cost‐effective heterogeneous catalysis, however, studies on its applications in electrocatalysis are still insufficient. Herein, it is reported that W18O49 nanowires supported sub‐nanometric Ru clusters (denoted as Ru SNC/W18O49 NWs) constitute an efficient bifunctional electrocatalyst for hydrogen evolution/oxidation reactions (HER and HOR) under acidic condition. Microstructural analyses, X‐ray absorption spectroscopy, and density functional theory (DFT) calculations reveal that the Ru SNCs with an average RuRu coordination number of 4.9 are anchored to the W18O49 NWs via RuOW bonds at the interface. The strong metal‐support interaction leads to the electron‐deficient state of Ru SNCs, which enables a modulated RuH strength. Furthermore, the unique proton transport capability of the W18O49 also provides a potential migration channel for the reaction intermediates. These components collectively enable the remarkable performance of Ru SNC/W18O49 NWs for hydrogen electrocatalysis with 2.5 times of exchange current density than that of carbon‐supported Ru nanoparticles, and even rival the state‐of‐the‐art Pt catalyst. This work provides a new prospect for the development of supported sub‐nanometric metal clusters for efficient electrocatalysis. Sub‐nanometric Ru clusters loaded with W18O49 NWs are successfully prepared via a facile one‐pot hydrothermal method. Combined characterizations and theoretical calculations reveal that the strong electronic metal‐support interaction between Ru clusters and W18O49 optimizes the binding strength of hydrogen intermediate at Ru sites, which exhibits attractive performance for hydrogen electrocatalysis that rival the state‐of‐the‐art Pt.

Direct conversion of carbon dioxide to multicarbon products remains as a grand challenge in electrochemical CO₂ reduction. Various forms of oxidized copper have been demonstrated as electrocatalysts that still require large overpotentials. Here, we show that an ensemble of Cu nanoparticles (NPs) enables selective formation of C₂–C₃ products at low overpotentials. Densely packed Cu NP ensembles underwent structural transformation during electrolysis into electrocatalytically active cube-like particles intermixed with smaller nanoparticles. Ethylene, ethanol, and n-propanol are the major C₂–C₃ products with onset potential at −0.53 V (vs. reversible hydrogen electrode, RHE) and C₂–C₃ faradaic efficiency (FE) reaching 50% at only −0.75 V. Thus, the catalyst exhibits selective generation of C₂–C₃ hydrocarbons and oxygenates at considerably lowered overpotentials in neutral pH aqueous media. In addition, this approach suggests new opportunities in realizing multicarbon product formation from CO₂, where the majority of efforts has been to use oxidized copper-based materials. Robust catalytic performance is demonstrated by 10 h of stable operation with C₂–C₃ current density 10 mA/cm² (at −0.75 V), rendering it attractive for solar-to-fuel applications. Tafel analysis suggests reductive CO coupling as a rate determining step for C₂ products, while n-propanol (C₃) production seems to have a discrete pathway.

HighlightsSynthesis protocols, design engineering, theoretical calculations, and energy applications for metal–organic frameworks (MOFs)-derived electrocatalysts are systematically analyzed.Synthesizing methods of MOF-derived catalysts and their oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction electrocatalysis are discussed.The current status, ongoing challenges, and potential future outlooks of MOFs-derived electrocatalysts are highlighted.The core reactions for fuel cells, rechargeable metal–air batteries, and hydrogen fuel production are the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), which are heavily dependent on the efficiency of electrocatalysts. Enormous attempts have previously been devoted in non-noble electrocatalysts born out of metal–organic frameworks (MOFs) for ORR, OER, and HER applications, due to the following advantageous reasons: (i) The significant porosity eases the electrolyte diffusion; (ii) the supreme catalyst–electrolyte contact area enhances the diffusion efficiency; and (iii) the electronic conductivity can be extensively increased owing to the unique construction block subunits for MOFs-derived electrocatalysis. Herein, the recent progress of MOFs-derived electrocatalysts including synthesis protocols, design engineering, DFT calculations roles, and energy applications is discussed and reviewed. It can be concluded that the elevated ORR, OER, and HER performances are attributed to an advantageously well-designed high-porosity structure, significant surface area, and plentiful active centers. Furthermore, the perspectives of MOF-derived electrocatalysts for the ORR, OER, and HER are presented.

Explore green catalytic reactions with this reference from a renowned leader in the field Green reactions-like photo-, photoelectro-, and electro-catalytic reactions-offer viable technologies to solve difficult problems without significant damage to the environment. In particular, some gas-involved reactions are especially useful in the creation of liquid fuels and cost-effective products. In Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction, award-winning researcher Jianmin Ma delivers a comprehensive overview of photo-, electro-, and photoelectron-catalysts in a variety of processes, including O2 reduction, CO2 reduction, N2 reduction, H2 production, water oxidation, oxygen evolution, and hydrogen evolution. The book offers detailed information on the underlying mechanisms, costs, and synthetic methods of catalysts. Filled with authoritative and critical information on green catalytic processes that promise to answer many of our most pressing energy and environmental questions, this book also includes: Thorough introductions to electrocatalytic oxygen reduction and evolution reactions, as well as electrocatalytic hydrogen evolution reactions Comprehensive explorations of electrocatalytic water splitting, CO2 reduction, and N2 reduction Practical discussions of photoelectrocatalytic H2 production, water splitting, and CO2 reduction In-depth examinations of photoelectrochemical oxygen evolution and nitrogen reductionPerfect for catalytic chemists and photochemists, Photo- and Electro-Catalytic Processes: Water Splitting, N2 Fixing, CO2 Reduction also belongs in the libraries of materials scientists and inorganic chemists seeking a one-stop resource on the novel aspects of photo-, electro-, and photoelectro-catalytic reactions.

Gas-involving electrochemical reactions, like oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), are critical processes for energy-saving, environment-friendly energy conversion and storage technologies which gain increasing attention. The development of according electrocatalysts is key to boost their electrocatalytic performances. Dramatic efforts have been put into the development of advanced electrocatalysts to overcome sluggish kinetics. On the other hand, the electrode interfaces-architecture construction plays an equally important role for practical applications because these imperative electrode reactions generally proceed at triple-phase interfaces of gas, liquid electrolyte, and solid electrocatalyst. A desirable architecture should facilitate the complicate reactions occur at the triple-phase interfaces, which including mass diffusion, surface reaction and electron transfer. In this review, we will summarize some design principles and synthetic strategies for optimizing triple-phase interfaces of gas-involving electrocatalysis systematically, based on the electrode reaction process at the three-phase interfaces. It can be divided into three main optimization directions: exposure of active sites, promotion of mass diffusion and acceleration of electron transfer. Furthermore, we especially highlight several remarkable works with comprehensive optimization about specific energy conversion devices, including metal-air batteries, fuel cells, and water-splitting devices are demonstrated with superb efficiency. In the last section, the perspectives and challenges in the future are proposed.