Single-phase perovskite oxide with super-exchange induced atomic-scale synergistic active centers enables ultrafast hydrogen evolution

Enhancing electrocatalytic performance in the oxygen evolution reaction of zirconium-based amorphous high-entropy oxides via controlled introduction of oxygen vacancies: experimental insights and DFT simulations

The controlled introduction of oxygen vacancies (Ovac) offers a promising strategy for enhancing the catalytic activity of materials. In this study, we effectively modulated the concentration of Ovac in the zirconium-based amorphous high-entropy oxides (HEOs) by optimizing the Zr cation content. This adjustment facilitated precise tuning of the d-band center and chemical activity of Zr active sites, leading to substantial improvements in electrocatalytic performance for the oxygen evolution reaction (OER). Among the prepared zirconium-based materials, the HEO-Zr1.0 specimen demonstrated outstanding OER electrocatalytic performance, achieving an overpotential of 257 mV at 10 mA cm-2 and 299 mV at 100 mA cm-2, a small Tafel slope of 40.3 mV dec-1. At the same time, the HEO-Zr1.0||HEO-Zr1.0 cell demonstrates excellent performance in complete water splitting. These findings underscore the effectiveness of moderate Ovac concentrations in enhancing catalytic activity, as confirmed by both experimental data and density functional theory simulations. This approach of controlled Ovac introduction provides a viable path for optimizing HEO catalytic performance, offering valuable insights for advancing electrocatalytic applications.

Phenol-driven ammonium recovery from coal chemical wastewater in a bioelectrochemical system (BES)

Bioelectrochemical systems (BES) have gained considerable attention in the past decade as a potentially sustainable and cost-effective method for coal chemical wastewater (CCW) treatment. However, a scarcity of studies focusing on the recovery NH4+-N in the recycling treatment of CCW via BES technology. In this study, a BES-ammonium recovery system (BES-ARS) was proposed to remove phenol and NH4+-N simultaneously, while NH4+-N was further recovered in a downstream recovery unit. Through systematic evaluation, we identified optimal condition for both phenol and NH4+-N removal. Specifically, an influent phenol-to-ammonium ratio of 2.0 was found to be ideal for maximizing simultaneous removal efficiency. Additionally, an evaluation of the nitrogen distribution showed that 97.9 % of NH4+-N migrated to the cathode chamber, with 82.5 % of NH4+-N being recovered in the absorbent under optimal condition. Furthermore, the solution not only reduces operational costs by up to 68 % compared to conventional treatments, but also conserves energy. This study presents an efficient and environmentally friendly treatment method for treating CCW, while recovering NH4+-N as a valuable resource.

Machine Learning Tailored Anodes for Efficient Hydrogen Energy Generation in Proton-Conducting Solid Oxide Electrolysis Cells

In the global trend of vigorously developing hydrogen energy, proton-conducting solid oxide electrolysis cells (P-SOECs) have attracted significant attention due to their advantages of high efficiency and not requiring precious metals. However, the application of P-SOECs faces challenges, particularly in developing high-performance anodes possessing both high catalytic activity and ionic conductivity. In this study, La0.9Ba0.1Co0.7Ni0.3O3-δ (LBCN9173) and La0.9Ca0.1Co0.7Ni0.3O3-δ (LCCN9173) oxides are tailored as promising anodes by machine learning model, achieving the synergistic enhancement of water oxidation reaction kinetics and proton conduction, which is confirmed by comprehensively analyzing experiment and density functional theory calculation results. Furthermore, the anodic reaction mechanisms for P-SOECs with these anodes are elucidated by analyzing distribution of relaxation time spectra and Gibbs energy of water oxidation reaction, manifesting that the dissociation of H2O is facilitated on LBCN9173 anode. As a result, P-SOEC with LBCN9173 anode demonstrates a top-rank current density of 2.45 A cm-2 at 1.3 V and an extremely low polarization resistance of 0.05 Ω cm2 at 650 °C. This multi-scale, multi-faceted research approach not only discovered a high-performance anode but also proved the robust framework for the machine learning-assisted design of anodes for P-SOECs.

Monophasic Titanate-Based Photocatalyst with Heteroatom Mixed Iso-Aliovalency Enabling Water Oxidation

Rhodium-doped SrTiO3 perovskite as a monophasic titanate-based catalyst (SrTi1-xRhxO3) showed photocatalytic activity for oxygen evolution reaction (OER) from water under solar light irradiation with an instant induction period, although Rh4+ in SrTiO3 introduces deep trap states thereby diminishing the efficiency of the hydrogen evolution reaction (HER). Despite its potential, the exact crystal structure of Rh:SrTiO3 has not been yet completely investigated. Overcoming these challenges, here, we synthesized a monophasic SrTi0.95Rh0.05O3 (RSTO) perovskite oxide with a precisely determined crystal structure and highlighted an unconsidered pivotal role of the Rh iso-aliovalency reversibility that enables excellent photocatalytic water oxidation. With structural, morphological, optical, and electronic insights from XRD, FE-SEM, HR-TEM, XPS, and advanced XAS measurements in both total electron yield (TEY) and fluorescence yield (TFY), the oxygen evolution reaction (OER) process is attributed to the redox dynamics of Rh4+ ↔ Rh3+ synergistic interplay.

Toward the Ideal Alkaline Hydrogen Evolution Electrocatalyst: a Noble Metal-Free Antiperovskite Optimized with A-Site Tuning

To achieve the ideal non-noble-metal HER electrocatalyst in alkaline media, developing conductive systems with multiple active sites targeting every elementary step in the alkaline HER, is highly desirable but remains a great challenge. Herein, a conductive noble metal-free antiperovskite CdNNi3 is reported with intrinsic metallic characteristics as a highly efficient alkaline HER electrocatalyst, which is designed by the facile A-site tuning strategy with the modulation the electronic structures and interfacial water configurations of antiperovskites. Impressively, the HER performance of CdNNi3 antiperovskite is superior to various state-of-the-art non-noble metal catalysts ever reported, and also outperforms the commercial Raney Ni catalyst when assemble as the cathode in the practical anion exchange membrane water electrolyzer (AEMWE) device. With insights from comprehensive experiments and theoretical calculations, the CdNNi3 can create synergistic dual active sites for catalyzing different elementary steps of the alkaline HER; namely, the Ni site can effectively facilitate the H2O dissociation and OH- desorption, while the unusual Cd-Ni bridge site is active for the optimal H* adsorption and H2 evolution. Such multifunction-site synergy, together with inherent high electrical conductivity, enables the CdNNi3 antiperovskite to fulfill the essential criteria for an ideal non-noble-metal alkaline HER electrocatalyst with excellent performance.

One-Step Molten Salt Constructing Double S-Scheme K0.2WO3/NiO/NiWO4 Heterojunction for Photocatalytic CO2 Reduction

Rapid charge separation and transfer is the key scientific problem in photocatalysis. The construction of S-scheme heterojunction is one of the effective strategies to promote charge separation and maintain the strong redox properties. Herein, the NiO, K0.2WO3, and NiWO4 ternary double S-scheme K0.2WO3/NiO/NiWO4 heterojunction (W/NiO) was created by a one-step molten salt method. Ultraviolet-visible (UV-Vis) diffuse reflectance spectra, photoluminescence (PL) spectra, photoelectrochemistry tests, and other analyses revealed that the double S-scheme heterostructure broadened the spectral response range of NiO and promoted its separation of photocarriers. Compared with pristine NiO, the modified double S-scheme heterojunction enhanced the surface adsorption of water molecules and the accumulation of intermediate product of HCOO-, and optimized the CO2 reduction system, realizing the improved CO yield of 373 μmol·g-1·h-1 in Ru(byp)32+/ethanolamine of CO2 reduction system. This study indicates that double S-scheme heterojunction could facilitate efficient photogenerated charge transfer and separation, thereby achieving high activity and selectivity for CO2 photoreduction. Our work provides a reference for the one-step construction of double S-scheme heterojunction.

Reductive Supramolecular In Situ Construction of Nano-Platinum Effectively Couples Cathodic Hydrogen Evolution and Anodic Alcohol Oxidation

The deployment of high-performance catalysts and the acceleration of anodic reaction kinetics are key measures to achieve maximum energy efficiency in overall water electrolysis hydrogen production systems. Here, an innovative strategy is developed by directly constructing a supramolecular framework embedded with boron clusters and cucurbituril as reducing agent. This approach enabled the in situ conversion of Pt⁴⁺ into highly dispersed, small-sized nano-platinum, which are subsequently distributed on a boron-carbon-nitrogen (BCN) matrix. The resulting Pt/BNHCSs catalyst demonstrates the ability to facilitate electrocatalytic water splitting for hydrogen production across multiple scenarios while simultaneously accelerating the anodic methanol oxidation kinetics, significantly outperforming commercial Pt/C catalyst in various aspects. The cathodic hydrogen evolution-anodic methanol oxidation coupling system constructed using the Pt/BNHCSs greatly reduces the overall energy consumption of the electrolysis system. In situ attenuated total reflection Fourier transform infrared and online differential electrochemical mass spectrometry reveals that the catalyst interface enhances H₂O adsorption and promotes the CH₃OH→CO conversion process, and density functional theory calculations indicated that the BCN support facilitated the evolution of H₂O to H₂ and CH₃OH to CO, elucidating the mechanism by which Pt/BNHCSs simultaneously promoted hydrogen production and methanol oxidation.

TiO2/LaFeO3 Composites for the Efficient Degradation of Benzoic Acid and Hydrogen Production

LaFeO3/TiO2 composites were prepared in the range 0-12.2 wt% of LaFeO3, characterized, and tested for both benzoic acid (BA) and 4-methoxycinnamic acid (MCA) degradation in aqueous solution, and hydrogen evolution. The preparation method was via ball-milling without thermal treatment. The composite materials presented agglomerates of LaFeO3 with an average size from 1 to 5 μm, and the TiO2 powder was well dispersed onto the surface of each sample. They showed varying activities for BA degradation depending on composition and light wavelength. The 6.2 wt% and 12.2 wt%-LaFeO3/TiO2 composites exhibited the highest activity under 380-800 nm light and could degrade BA in 300 min at BA concentration 13.4 mg L-1 and catalyst 0.12 g L-1. Using a 450 nm LED light source, all composites degraded less than 10% of BA, but in the presence of H2O2 (1 mM) the photocatalytic activity was as high as 96% in <120 min, 6.2 wt%-LaFeO3/TiO2 composite being the most efficient sample. It was found that in the presence of H2O2, BA degradation followed first order kinetic with a reaction rate constant of 4.8 × 10-4 s-1. The hydrogen production rate followed a classical volcano-like behavior, with the highest reactivity (1600 μmol h-1g-1 at 60 °C) in the presence of 3.86%wt- LaFeO3/TiO2. It was also found that LaFeO3/TiO2 exhibited high stability in four recycled tests without losing activity for hydrogen production. Furthermore, a discussion on photogenerated charge-carrier transfer mechanism is briefly provided, focusing on lacking significant photocatalytic activity under 450 nm light, so p-n heterojunction formation is unlikely.

Perovskite Type ABO3 Oxides in Photocatalysis, Electrocatalysis, and Solid Oxide Fuel Cells: State of the Art and Future Prospects

Since photocatalytic and electrocatalytic technologies are crucial for tackling the energy and environmental challenges, significant efforts have been put into exploring advanced catalysts. Among them, perovskite type ABO3 oxides show great promising catalytic activities because of their flexible physical and chemical properties. In this review, the fundamentals and recent progress in the synthesis of perovskite type ABO3 oxides are considered. We describe the mechanisms for electrocatalytic oxygen evolution reactions (OER), oxygen reduction reactions (ORR), hydrogen evolution reactions (HER), nitrogen reduction reactions (NRR), carbon dioxide reduction reactions (CO2RR), and metal-air batteries in details. Furthermore, the photocatalytic water splitting, CO2 conversion, pollutant degradation, and nitrogen fixation are reviewed as well. We also stress the applications of perovskite type ABO3 oxides in solid oxide fuel cells (SOFs). Finally, the optimization of perovskite type ABO3 oxides for applications in various fields and an outlook on the current and future challenges are depicted. The aim of this review is to present a broad overview of the recent advancements in the development of perovskite type ABO3 oxides-based catalysts and their applications in energy conversion and environmental remediation, as well as to present a roadmap for future development in these hot research areas.

Boosting Alkaline Hydrogen Evolution by Creating Atomic-Scale Pair Cocatalytic Sites in Single-Phase Single-Atom-Ruthenium-Incorporated Cobalt Oxide

Compared with acidic environments, promoting the water dissociation process is crucial for speeding up hydrogen evolution reaction (HER) kinetics in alkaline electrolyte. Although the construction of heterostructured electrocatalysts by hybridizing noble metals with metal (hydr)oxides has been reported as a feasible approach to achieve high performance, the high cost, complicated fabrication process, and unsatisfactory mass activity limit their large-scale applications. Herein, we report a single-phase HER electrocatalyst composed of single-atom ruthenium (Ru) incorporated into a cobalt oxide spine structure (denoted as Ru SA/Co3O4), which possesses exceptional HER performance in alkaline media via unusual atomic-scale Ru-Co pair sites. In particular, Ru SA/Co3O4 exhibits a very low overpotential of 44 mV at 10 mA cm-2 and an outstanding mass activity of 4700 mA mg-1 at 50 mV overpotential, superior to those of commercial Pt/C, Ru nanoparticles supported on Co3O4 (denoted as Ru NP/Co3O4) and other reported Ru-based electrocatalysts. With insights from theoretical calculations, the synergistic interactions between Ru and Co pair active sites in Ru SA/Co3O4 are revealed to catalyze diverse fundamental steps of the alkaline HER; i.e., the Ru sites can effectively accelerate water adsorption/dissociation and OH- desorption, whereas the Co sites are favorable for H* adsorption and H2 evolution.

Realizing the Synergy of Interface and Dual-Defect Engineering for Molybdenum Disulfide Enables Efficient Sodium-Ion Storage

Engineering-rich electrocatalyst defects play a critical role in greatly promoting the charge storage/transfer capability of an energy storage/conversion system. Here, an ingenious and effective two-step strategy was used to synthesize a bimetallic sulfide/oxide composite with a coaxial carbon coating, starting from mixing well-dispersed MoO3 nanobelts and Co-PAA compound, followed by a selective etching process. The simultaneous formation of dual defects of interlayer defect and sulfur-rich vacancies as well as MoO2/MoS2-x/CoS heterojunctions noticeably enhances both electron transfer and ion diffusion kinetics. The ultrathin carbon protective layer on the surface of the composite ensures its high conductivity and excellent structural stability. The composite electrode shows a high reversible capacity (158.3 mAh g-1 at 10 A g-1 after 4000 cycles) and outstanding long-cycle stability (0.04% per cycle over 2100 cycles at 20 A g-1). A full cell based on MoO2/MoS2-x/CoS@N, S-C anode, and Na3V2(PO4)3 cathode can maintain a reversible capacity of 128.1 mAh g-1 after 600 cycles at 1 A g-1, surpassing that based on MoO2/MoS2 and is very comparable in performance with the state-of-the-art Na-ion full cells. Moreover, density functional theory (DFT) calculations, electrochemical kinetics analysis, and in situ Raman and ex-situ X-ray diffraction characterization were carried out to elucidate the involved scientific mechanisms of sodium storage.

Microwave-Assisted Doping Engineering Construction of Spinel-Structured Nonstoichiometric Manganese Cobaltite with Mixed 1D/2D Morphology for Supercapacitor Application

High-performance electrode materials are fundamental to improving supercapacitor performance, serving as key factors in developing devices with high energy density, high power density, and excellent cyclic stability. Non-stoichiometric spinels with phase deficiencies can achieve electrochemical performance that surpasses that of stoichiometric materials, owing to their unique structural characteristics. In this study, we used a microwave-assisted method to synthesize a high-performance non-stoichiometric spinel material with phase deficiencies, Mn0.5Co2.5O4, which displayed a wide potential window (1.13 V in a traditional aqueous three-electrode system) and high specific capacitance (716.9 F g-1 at 1 A g-1). More critically, through microwave-assisted doping engineering, nickel was successfully doped into the phase-deficient Mn0.5Co2.5O4, resulting in a spinel material, Ni-Mn0.5Co2.5O4, with significant lattice defects and a mixed 1D/2D morphology. The doping of nickel effectively promoted the high-state conversion of manganese valence states within the manganese cobaltite material, substantially increasing the quantity of highly active Co3+ ions. These changes led to an increase in the density of reactive sites, effectively promoting synergistic interactions, thereby significantly enhancing the material's conductivity and energy storage performance. The specific capacitance of Ni-Mn0.5Co2.5O4 reached 1180.6 F g-1 at 1 A g-1, a 64.7% improvement over the original Mn0.5Co2.5O4; at a high current density of 10 A g-1, the capacitance increased by 14.3%. Notably, the charge transfer resistance was reduced by a factor of 41.6. After 5000 cycles of testing, the capacity retention stood at 79.2%. This work reveals the effectiveness of microwave-assisted doping engineering in constructing high-performance non-stoichiometric spinel-type bimetallic oxide materials, offering advanced strategies for the development of high-performance electrode materials.

A Study of Redox Properties of Ceria and Fe-Ceria Solid Materials Through Small Molecules Catalytic Oxidation

This work presents a study of the redox properties of CeO2 particles with (FeCeHS) and without (CeHS) Fe2O3 impregnation, as possible innovative catalysts for oxidation and combustion reactions as well as CO2 activation. The topic, therefore, is part of a broader analysis of environmental catalysis, which aims to reduce the emissions of polluting substances and improve the exploitation of energy resources, with consequent progress in the eco-friendly field. Different laboratory techniques (Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Ultraviolet-Visible (UV-Vis), and Fourier Transform-Infrared (FT-IR) spectroscopies) point out that iron oxide is deposited on the surface of ceria, which maintains its lattice structure, although the particle morphology is slightly changed. Methanol and ethanol adsorption and conversion were evaluated on these catalysts by Temperature Programmed Surface Reaction (TPSR) and by in situ FT-IR spectroscopy of the probe redox properties, evidencing the formation of surface oxidized intermediates and combustion products. The FeCeHS catalyst demonstrates, in our reaction conditions, a good combustion activity in total oxidation of oxygenated molecules, hindering the formation of formaldehyde from methanol and reducing the quantity of CO produced by the partial oxidation reaction. A cooperative effect is suggested by the mixture of these two metals in the oxidation process.

Synthesis of Electrocatalytic Tungsten Carbide Nanoparticles by High-Pressure and High-Temperature Treatment of Organotungsten Compounds

Metal-organic framework (MOF)-derived carbon, which contains metal nanoparticles embedded in a carbon matrix, is becoming an important group of catalysts. We report the synthesis of tungsten carbide-carbon nanocomposites using a similar concept, i.e., by pyrolysis of organotungsten compounds under high-temperature and high-pressure conditions. We characterized the product using various analytical techniques and examined its electrocatalytic activity. Two precursors, Bis(cyclopentadienyl)tungsten (IV) dichloride (Cp2WCl2) and Bis(cyclopentadienyl)tungsten (IV) dihydride (Cp2WH2) were pyrolyzed at 4.5 GPa and 600 °C. Tungsten carbide (β-WC1-x) crystals with a size of 2 nm embedded in graphitic carbon were formed from Cp2WH2-derived samples. Electrochemical measurements showed that all samples were active in the oxygen reduction reaction (ORR), with the Cp2WH2-derived sample having the best catalytic performance.

Beyond conventional structures: emerging complex metal oxides for efficient oxygen and hydrogen electrocatalysis

The core of clean energy technologies such as fuel cells, water electrolyzers, and metal-air batteries depends on a series of oxygen and hydrogen-based electrocatalysis reactions, including the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), which necessitate cost-effective electrocatalysts to improve their energy efficiency. In the recent decade, complex metal oxides (beyond simple transition metal oxides, spinel oxides and ABO3 perovskite oxides) have emerged as promising candidate materials with unexpected electrocatalytic activities for oxygen and hydrogen electrocatalysis owing to their special crystal structures and unique physicochemical properties. In this review, the current progress in complex metal oxides for ORR, OER, and HER electrocatalysis is comprehensively presented. Initially, we present a brief description of some fundamental concepts of the ORR, OER, and HER and a detailed description of complex metal oxides, including their physicochemical characteristics, synthesis methods, and structural characterization. Subsequently, we present a thorough overview of various complex metal oxides reported for ORR, OER, and HER electrocatalysis thus far, such as double/triple/quadruple perovskites, perovskite hydroxides, brownmillerites, Ruddlesden-Popper oxides, Aurivillius oxides, lithium/sodium transition metal oxides, pyrochlores, metal phosphates, polyoxometalates and other specially structured oxides, with emphasis on the designed strategies for promoting their performance and structure-property-performance relationships. Moreover, the practical device applications of complex metal oxides in fuel cells, water electrolyzers, and metal-air batteries are discussed. Finally, some concluding remarks summarizing the challenges, perspectives, and research trends of this topic are presented. We hope that this review provides a clear overview of the current status of this emerging field and stimulate future efforts to design more advanced electrocatalysts.

Electrochemical Degradation of Sulfamethoxazole Enhanced by Bio-Inspired Iron-Nickel Encapsulated Biochar Particle Electrode

In the electrocatalytic (EC) degradation process, challenges such as inefficient mass transfer, suboptimal mineralization rates, and limited current efficiency have restricted its broader application. To overcome these obstacles, this study synthesized spherical particle electrodes (FeNi@BC) with superior electrocatalytic performance using a bio-inspired preparation method. A three-dimensional electrocatalytic oxidation system based on FeNi@BC electrode, EC/FeNi@BC, showed excellent degradation efficiency of sulfamethoxazole (SMX), reaching 0.0456 min-1. Quenching experiments and electron paramagnetic resonance experiments showed that the excellent SMX degradation efficiency in the EC/FeNi@BC system was attributed to the synergistic effect of multiple reactive oxygen species (ROS) and revealed their evolution path. Characterization results showed that FeNi3 generated in the FeNi@BC electrode was a key bimetallic active site for improving electrocatalytic activity and repolarization ability. More importantly, the degradation pathway and reaction mechanism of SMX in the EC/FeNi@BC system were proposed. In addition, the influencing factors of the reaction system (voltage, pH, initial SMX concentration, electrode dosage, and sodium sulfate concentration, etc.) and the stability of the catalyst (maintained more than 81% after 5 cycles) were systematically evaluated. This study may provide help for the construction of environmentally friendly catalytic and efficient degradation of organic pollutants.

A Complex Oxide Containing Inherent Peroxide Ions for Catalyzing Oxygen Evolution Reactions in Acid

Proton exchange membrane water electrolyzers powered by sustainable energy represent a cutting-edge technology for renewable hydrogen generation, while slow anodic oxygen evolution reaction (OER) kinetics still remains a formidable obstacle that necessitates basic comprehension for facilitating electrocatalysts' design. Here, we report a low-iridium complex oxide La1.2Sr2.7IrO7.33 with a unique hexagonal structure consisting of isolated Ir(V)O6 octahedra and true peroxide O22- groups as a highly active and stable OER electrocatalyst under acidic conditions. Remarkably, La1.2Sr2.7IrO7.33, containing 59 wt % less iridium relative to the benchmark IrO2, shows about an order of magnitude higher mass activity, 6-folds higher intrinsic activity than the latter, and also surpasses the state-of-the-art Ir-based oxides ever reported. Combined electrochemical, spectroscopic, and density functional theory investigations reveal that La1.2Sr2.7IrO7.33 follows the peroxide-ion participation mechanism under the OER condition, where the inherent peroxide ions with accessible nonbonded oxygen states are responsible for the high OER activity. This discovery offers an innovative strategy for designing advanced catalysts for various catalytic applications.

Bimetallic NiCo Nanoparticles Embedded in Organic Group Functionalized Mesoporous Silica for Efficient Hydrogen Production from Ammonia Borane Hydrolysis

In this study, bimetallic NiCo nanoparticles (NPs) were encapsulated within the mesopores of carboxylic acid functionalized mesoporous silica (CMS) through the chemical reduction approach. Both NaBH4 and NH3BH3 were used as reducing agents to reduce the metal ions simultaneously. The resulting composite was used as a catalyst for hydrolysis of ammonia borane (NH3BH3, AB) to produce H2. The bimetallic NiCo NPs supported on carboxylic group functionalized mesoporous silica, referred to as NixCo100-x@CMS, exhibited significantly higher catalytic activity for AB hydrolysis compared to their monometallic counterparts. The remarkable activity of NixCo100-x@CMS could be ascribed to the synergistic contributions of Ni and Co, redox reaction during the hydrolysis, and the fine-tuned electronic structure. The catalytic performance of the NixCo100-x@CMS nanocatalyst was observed to be dependent on the composition of Ni and Co. Among all the compositions investigated, Ni40Co60@CMS demonstrated the highest catalytic activity, with a turn over frequency (TOF) of 18.95 molH2min-1molcatalyst-1 and H2 production rate of 8.0 L min-1g-1. The activity of Ni40Co60@CMS was approximately three times greater than that of Ni@CMS and about two times that of Co@CMS. The superior activity of Ni40Co60@CMS was attributed to its finely-tuned electronic structure, resulting from the electron transfer of Ni to Co. Furthermore, the nanocatalyst exhibited excellent durability, as the carboxylate group in the support provided a strong metal-support interaction, securely anchoring the NPs within the mesopores, preventing both agglomeration and leakage.

Super-exchange interaction enables Fe2-xMnxO3 perovskite with excellent catalytic oxidation activity toward hexabromocyclododecane under humidity

Although enhancing the catalytic oxidation activity is a hotspot in thermal-driven catalytic disposal of persistent organic pollutants, few studies have managed to improve catalysts' water-resistance properties. Herein, we developed Fe2-xMnxO3 perovskite to boost the catalytic oxidation of hexabromocyclododecane under humidity by modulating its super-exchange interaction (SEI, Fe3+ + Mn3+ → Fe2+ + Mn4+). Fe0.4Mn1.6O3, with the strongest SEI, exhibits the biggest oxidation rate-constant, which is 3 times higher than that of commonly used Fe2O3 without SEI. Notably, unlike Fe2O3 which deactivates at a relative humidity of 5 %. Fe0.4Mn1.6O3 maintains its activity and is even boosted by 22 % compared to dry conditions. Mechanistic insights reveal that SEI between Fe and Mn enhances the reactivity of Mn4+- linked Olatt by lowering the reductive temperature from Mn4+ to Mn3+. Meanwhile, SEI promotes the adsorption of the associatively adsorbed H2O (HOH-type water) by reducing adsorption energy, thereby facilitating the formation of hydroxyl species, which are crucial for the oxidation process under humidity.

Ni Nanoparticles Supported on Graphene-Based Materials as Highly Stable Catalysts for the Cathode of Alkaline Membrane Fuel Cells

Ni nanoparticles supported on graphene-based materials were tested as catalysts for the oxygen reduction reaction (ORR) to be used in anion exchange membrane fuel cells (AEMFCs). The introduction of N into the graphene structure produced an enhancement of electrocatalytic activity by improving electron transfer and creating additional active sites for the ORR. Materials containing both N and S demonstrated the highest stability, showing only a 3% performance loss after a 10 h stability test and therefore achieving the best overall performance. This long-term durability is attributed to the synergetic effect of Ni nanoparticles and bi-doped (S/N)-reduced graphene oxide. The findings suggest that the strategic incorporation of both nitrogen and sulphur into the graphene structure plays a crucial role in optimising the electrocatalytic properties of Ni-based catalysts.

Deep Reconstruction of Ruthenate Perovskite Oxide Enables Efficient pH-Universal Hydrogen Evolution Reaction

Designing highly efficient, stable, and pH-universal perovskites for hydrogen evolution reaction (HER) is urgently needed yet remains a grand challenge. Herein, a titanium-containing strontium ruthenate (SrTi0.5Ru0.5O3, STRO) is developed as an excellent HER electrocatalyst in a wide pH range. The introduction of Ti into SrRuO3 significantly reduces the size of STRO, endowing with a high reactivity that facilitates a deep surface-reconstruction during HER. Furthermore, Sr2+ leaching triggered reconstruction leads to STRO breaking into tiny nanoparticles accompanied by high-valence ruthenium (Ru) species reducing to metallic Ru. The generated active species, increased accessible sites, and improved electrical conductivity greatly boost HER. The reconstructed STRO displays remarkable HER activities with exceptional low overpotentials of 18, 24, and 55 mV at 10 mA cm-2 in 1 m KOH, 0.5 m H2SO4, and 1 m PBS, respectively, surpassing most perovskites reported previously and comparable to or even outperforming that of commercial Pt/C. Moreover, the STRO exhibits excellent stabilities over 200 h in alkaline and acidic media, superior to that of Pt/C. This work not only provides insights into structure reconstruction of perovskites during HER, but also opens new perspectives for developing high-efficiency and pH-universal electrocatalysts for future energy applications.

In Situ Transformed CoOOH@Co3S4 Heterostructured Catalyst for Highly Efficient Catalytic OER Application

The deprived electrochemical kinetics of the oxygen evolution reaction (OER) catalyst is the prime bottleneck and remains the major obstacle in the water electrolysis processes. Herein, a facile hydrothermal technique was implemented to form a freestanding polyhedron-like Co3O4 on the microporous architecture of Ni foam, its reaction kinetics enhanced through sulfide counterpart transformation in the presence of Na2S, and their catalytic OER performances comparatively investigated in 1 M KOH medium. The formed Co3S4 catalyst shows outstanding catalytic OER activity at a current density of 100 mA cm-2 by achieving a relatively low overpotential of 292 mV compared to the pure Co3O4 catalyst and the commercial IrO2 catalyst. This enhancement results from the improved active centers and conductivity, which boost the intrinsic reaction kinetics. Further, the optimized Co3S4 catalyst exhibits admirable prolonged durability up to 72 h at varied current rates with insignificant selectivity decay. The energy dispersive X-ray spectroscopy (EDX) and Raman spectra measured after the prolonged OER stability test reveal a partial transformation of the active catalyst into an oxyhydroxide phase (i.e., CoOOH@Co3S4), which acts as an active catalyst phase during the electrolysis process.

Enhanced Photoelectrochemical Water Splitting of In2S3 Photoanodes by Surface Modulation with 2D MoS2 Nanosheets

Photoanodes with ample visible-light absorption and efficient photogenerated charge carrier dynamics expedite the actualization of high-efficiency photoelectrochemical water splitting (PEC-WS). Herein, we fabricated the heterojunction nanostructures of In2S3/MoS2 on indium-doped tin oxide glass substrates by indium sputtering and sulfurization, followed by the metal-organic chemical vapor deposition of 2D MoS2 nanosheets (NSs). The photocurrent density of In2S3/MoS2 was substantially enhanced and higher than those of pristine In2S3 and MoS2 NSs. This improvement is due to the MoS2 NSs extending the visible-light absorption range and the type-II heterojunction enhancing the separation and transfer of photogenerated electron-hole pairs. This work offers a promising avenue toward the development of an efficient photoanode for solar-driven PEC-WS.

Enhanced Photocatalytic Paracetamol Degradation by NiCu-Modified TiO2 Nanotubes: Mechanistic Insights and Performance Evaluation

Anodic TiO2 nanotube arrays decorated with Ni, Cu, and NiCu alloy thin films were investigated for the first time for the photocatalytic degradation of paracetamol in water solution under UV irradiation. Metallic co-catalysts were deposited on TiO2 nanotubes using magnetron sputtering. The influence of the metal layer composition and thickness on the photocatalytic activity was systematically studied. Photocatalytic experiments showed that only Cu-rich co-catalysts provide enhanced paracetamol degradation rates, whereas Ni-modified photocatalysts exhibit no improvement compared with unmodified TiO2. The best-performing material was obtained by sputtering a 20 nm thick film of 1:1 atomic ratio NiCu alloy: this material exhibits a reaction rate more than doubled compared with pristine TiO2, enabling the complete degradation of 10 mg L-1 of paracetamol in 8 h. The superior performance of NiCu-modified systems over pure Cu-based ones is ascribed to a Ni and Cu synergistic effect. Kinetic tests using selective holes and radical scavengers unveiled, unlike prior findings in the literature, that paracetamol undergoes direct oxidation at the photocatalyst surface via valence band holes. Finally, Chemical Oxygen Demand (COD) tests and High-Resolution Mass Spectrometry (HR-MS) analysis were conducted to assess the degree of mineralization and identify intermediates. In contrast with the existing literature, we demonstrated that the mechanistic pathway involves direct oxidation by valence band holes.

Structural evolution and catalytic mechanisms of perovskite oxides in electrocatalysis

Electrocatalysis plays a pivotal role in driving the progress of modern technologies and industrial processes such as energy conversion and emission reduction. Perovskite oxides, an important family of electrocatalysts, have garnered substantial attention in diverse catalytic reactions because of their highly tunable composition and structure, as well as their considerable activity and stability. This review delves into the mechanisms of electrocatalytic reactions that use perovskite oxides as electrocatalysts, while also providing a comprehensive summary of the potential key factors that influence catalytic activity across various reactions. Furthermore, this review offers an overview of advanced characterizations used for studying catalytic mechanisms and proposes approaches to designing highly efficient perovskite oxide electrocatalysts.

Spin-dependent electrocatalysis

The shift towards sustainable energy requires efficient electrochemical conversion technologies, emphasizing the crucial need for robust electrocatalyst design. Recent findings reveal that the efficiency of some electrocatalytic reactions is spin-dependent, with spin configuration dictating performance. Consequently, understanding the spin's role and controlling it in electrocatalysts is important. This review succinctly outlines recent investigations into spin-dependent electrocatalysis, stressing its importance in energy conversion. It begins with an introduction to spin-related features, discusses characterization techniques for identifying spin configurations, and explores strategies for fine-tuning them. At the end, the article provides insights into future research directions, aiming to reveal more unknown fundamentals of spin-dependent electrocatalysis and encourage further exploration in spin-related research and applications.

Activating Inert Perovskite Oxides for CO2 Electroreduction via Slight Cu2+ Doping in B-Sites

Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x = 0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x = 0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.

Lattice Strain with Stabilized Oxygen Vacancies Boosts Ceria for Robust Alkaline Hydrogen Evolution Outperforming Benchmark Pt

Earth-abundant metal oxides are usually considered as stable but catalytically inert toward hydrogen evolution reaction (HER) due to their unfavorable hydrogen intermediate adsorption performance. Herein, a heavy rare earth (Y) and transition metal (Co) dual-doping induced lattice strain and oxygen vacancy stabilization strategy is proposed to boost CeO2 toward robust alkaline HER. The induced lattice compression and increased oxygen vacancy (Ov) concentration in CeO2 synergistically improve the water dissociation on Ov sites and sequential hydrogen adsorption at activated Ov-neighboring sites, leading to significantly enhanced HER kinetics. Meanwhile, Y doping offers stabilization effect on Ov by its stronger Y─O bonding over Ce─O, which endows the catalyst with excellent stability. The Y,Co-CeO2 electrocatalyst exhibits an ultra-low HER overpotential (27 mV at 10 mA cm-2) and Tafel slope (48 mV dec-1), outperforming the benchmark Pt electrocatalyst. Moreover, the anion exchange membrane water electrolyzer incorporated with Y,Co-CeO2 achieves excellent stability of 500 h under 600 mA cm-2. This synergistic lattice strain and oxygen vacancy stabilization strategy sheds new light on the rational development of efficient and stable oxide-based HER electrocatalysts.

Promoting CO2 Electroreduction Over Nano-Socketed Cu/Perovskite Heterostructures via A-Site-Valence-Controlled Oxygen Vacancies

Despite the intriguing potential, nano-socketed Cu/perovskite heterostructures for CO2 electroreduction (CO2RR) are still in their infancy and rational optimization of their CO2RR properties is lacking. Here, an effective strategy is reported to promote CO2-to-C2+ conversion over nano-socketed Cu/perovskite heterostructures by A-site-valence-controlled oxygen vacancies. For the proof-of-concept catalysts of Cu/La0.3-xSr0.6+xTiO3-δ (x from 0 to 0.3), their oxygen vacancy concentrations increase controllably with the decreased A-site valences (or the increased x values). In flow cells, their activity and selectivity for C2+ present positive correlations with the oxygen vacancy concentrations. Among them, the Cu/Sr0.9TiO3-δ with most oxygen vacancies shows the optimal activity and selectivity for C2+. And relative to the Cu/La0.3Sr0.6TiO3-δ with minimum oxygen vacancies, the Cu/Sr0.9TiO3-δ exhibits marked improvements (up to 2.4 folds) in activity and selectivity for C2+. The experiments and theoretical calculations suggest that the optimized performance can be attributed to the merits provided by oxygen vacancies, including the accelerated charge transfer, enhanced adsorption/activation of reaction species, and reduced energy barrier for C─C coupling. Moreover, when explored in a membrane-electrode assembly electrolyzer, the Cu/Sr0.9TiO3-δ catalyst shows excellent activity, selectivity (43.9%), and stability for C2H4 at industrial current densities, being the most effective perovskite-based catalyst for CO2-to-C2H4 conversion.

Efficient reduction-oxidation coupling degradation of nitroaromatic compounds in continuous flow processes

Nitroaromatic compounds (NACs) with electron-withdrawing nitro (-NO2) groups are typical refractory pollutants. Despite advanced oxidation processes (AOPs) being appealing degradation technologies, inefficient ring-opening oxidation of NACs and practical large-scale applications remain challenges. Here we tackle these challenges by designing a reduction-oxidation coupling (ROC) degradation process in LaFe0.95Cu0.05O3@carbon fiber cloth (LFCO@CFC)/PMS/Vis continuous flow system. Cu doping enhances the photoelectron transfer, thus triggering the -NO2 photoreduction and breaking the barriers in the ring opening. Also, it modulates surface electronic configuration to generate radicals and non-radicals for subsequent oxidation of reduction products. Based on this, the ROC process can effectively remove and mineralize NACs under the environmental background. More importantly, the LFCO catalyst outperformed most of the recently reported catalysts with lower cost (13.72 CNY/ton) and higher processing capacity (3600 t/month). Furthermore, the high scalability, material durability, and catalytic activity of LFCO@CFC under various realistic environmental conditions prove the potential ability for large-scale applications.

P-Incorporation Induced Enhancement of Lattice Oxygen Participation in Double Perovskite Oxides to Boost Water Oxidation

Activating the lattice oxygen in the catalysts to participate in the oxygen evolution reaction (OER), which can break the scaling relation-induced overpotential limitation (> 0.37 V) of the adsorbate evolution mechanism, has emerged as a new and highly effective guide to accelerate the OER. However, how to increase the lattice oxygen participation of catalysts during OER remains a major challenge. Herein, P-incorporation induced enhancement of lattice oxygen participation in double perovskite LaNi0.58Fe0.38P0.07O3-σ (PLNFO) is studied. P-incorporation is found to be crucial for enhancing the OER activity. The current density reaches 1.35 mA cmECSA -2 at 1.63 V (vs RHE), achieving a sixfold increase in intrinsic activity. Experimental evidences confirm the dominant lattice oxygen participation mechanism (LOM) for OER pathway on PLNFO. Further electronic structures reveal that P-incorporation shifts the O p-band center by 0.7 eV toward the Fermi level, making the states near the Fermi level more O p character, thus facilitating LOM and fast OER kinetics. This work offers a possible method to develop high-performance double perovskite OER catalysts for electrochemical water splitting.

Graphdiyne Enabled Nitrogen Vacancy Formation in Copper Nitride for Efficient Ammonia Synthesis

The electrocatalytic reduction of nitrate is promising for sustainable ammonia synthesis but suffers from slow reduction kinetics and multiple competing reactions. Here, we report a catalyst featuring copper nitride (Cu3N) anchored on a novel graphdiyne support (termed Cu3N/GDY), which is used for electrocatalytic reduction of nitrate to produce ammonia. The GDY absorbed hydrogen and enabled nitrogen (N) vacancy formation in Cu3N for the fast nitrate reduction reaction (NO3RR). Further, the distinct absorption sites formed by GDY and N vacancy enabled the excellent selectivity and stability of NO3RR. Notably, the Cu3N/GDY catalyst achieved a high ammonia yield (YNH3) up to 35280 μg h-1 mgcat.-1 and a high Faradaic efficiency (FE) of 98.1% using 0.1 M NO3- at -0.9 V versus a reversible hydrogen electrode (RHE). Using electron paramagnetic resonance (EPR) technology and in situ X-ray absorption fine structure (XAFS) spectroscopy measurement, we visualized the N vacancy formation in Cu3N and electrocatalytic NO3RR enabled by GDY. These findings show the promise of GDY in sustainable ammonia synthesis and highlight the efficacy of Cu3N/GDY as a catalyst.

Cobalt Single-Atom Reverse Hydrogen Spillover for Efficient Electrochemical Water Dissociation and Dechlorination

Efficient water dissociation to atomic hydrogen (H*) with restrained recombination of H* is crucial for improving the H* utilization for electrochemical dechlorination, but is currently limited by the lack of feasible electrodes. Herein, we developed a monolithic single-atom electrode with Co single atoms anchored on the inherent oxide layer of titanium foam (Co1-TiOx/Ti), which can efficiently dissociate water into H* and simultaneously inhibit the recombination of H*, by taking advantage of the single-atom reverse hydrogen spillover effect. Experimental and theoretical calculations demonstrated that H* could be rapidly generated on the oxide layer of titanium foam, and then overflowed to the adjacent Co single atom for the reductive dechlorination. Using chloramphenicol as a proof-of-concept verification, the resulting Co1-TiOx/Ti monolithic electrode exhibited an unprecedented performance with almost 100 % dechlorination at -1.0 V, far superior to that of traditional indirect reduction-driven commercial Pd/C (52 %) and direct reduction-driven Co1-N-C (44 %). Moreover, its dechlorination rate constant of 1.64 h-1 was 4.3 and 8.6 times more active than those of Pd/C (0.38 h-1) and Co1-N-C (0.19 h-1), respectively. Our research sheds light on the rational design of hydrogen spillover-related electrocatalysts to simultaneously improve the H* generation, transfer, and utilization for environmental and energy applications.

Linearly Interlinked Fe-Nx-Fe Single Atoms Catalyze High-Rate Sodium-Sulfur Batteries

Linearly interlinked single atoms offer unprecedented physiochemical properties, but their synthesis for practical applications still poses significant challenges. Herein, linearly interlinked iron single-atom catalysts that are loaded onto interconnected carbon channels as cathodic sulfur hosts for room-temperature sodium-sulfur batteries are presented. The interlinked iron single-atom exhibits unique metallic iron bonds that facilitate the transfer of electrons to the sulfur cathode, thereby accelerating the reaction kinetics. Additionally, the columnated and interlinked carbon channels ensure rapid Na+ diffusion kinetics to support high-rate battery reactions. By combining the iron atomic chains and the topological carbon channels, the resulting sulfur cathodes demonstrate effective high-rate conversion performance while maintaining excellent stability. Remarkably, even after 5000 cycles at a current density of 10 A g-1, the Na-S battery retains a capacity of 325 mAh g-1. This work can open a new avenue in the design of catalysts and carbon ionic channels, paving the way to achieve sustainable and high-performance energy devices.

Oxygen-deficient tungsten oxide inducing electron and proton transfer: Activating ruthenium sites for hydrogen evolution in wide pH and alkaline seawater

The design of electrocatalysts for the hydrogen evolution reaction (HER) that perform effectively across a broad pH spectrum is paramount. The efficiency of hydrogen evolution at ruthenium (Ru) active sites, often hindered by the kinetics of water dissociation in alkaline or neutral conditions, requires further enhancement. Metal oxides, due to superior electron dynamics facilitated by oxygen vacancies (OVS) and shifts in the Fermi level, surpass carbon-based materials. In particular, tungsten oxide (WO3) promotes the directed migration of electrons and protons which significantly activates the Ru sites. Ru/WO3-OV is prepared through a simple hydrothermal and low-temperature annealing process. The prepared catalyst achieves 10 mA cm-2 at overpotentials of 23 mV (1 M KOH), 36 mV (0.5 M H2SO4), 62 mV (1 M PBS), and 38 mV (1 M KOH + seawater). At an overpotential corresponding to 10 mA cm-2 in 1 M KOH and 1 M KOH + seawater, the mass activity of Ru/WO3-OV is about 7.7 and 7.86 times that of 20 wt% Pt/C. The improvement in activity and stability arises from electronic modifications attributed to metal-support interaction. This work offers novel insights for modulating the HER activity of Ru sites across a wide pH range.

Constructing regulable supports via non-stoichiometric engineering to stabilize ruthenium nanoparticles for enhanced pH-universal water splitting

Establishing appropriate metal-support interactions is imperative for acquiring efficient and corrosion-resistant catalysts for water splitting. Herein, the interaction mechanism between Ru nanoparticles and a series of titanium oxides, including TiO, Ti4O7 and TiO2, designed via facile non-stoichiometric engineering is systematically studied. Ti4O7, with the unique band structure, high conductivity and chemical stability, endows with ingenious metal-support interaction through interfacial Ti-O-Ru units, which stabilizes Ru species during OER and triggers hydrogen spillover to accelerate HER kinetics. As expected, Ru/Ti4O7 displays ultralow overpotentials of 8 mV and 150 mV for HER and OER with a long operation of 500 h at 10 mA cm-2 in acidic media, which is expanded in pH-universal environments. Benefitting from the excellent bifunctional performance, the proton exchange membrane and anion exchange membrane electrolyzer assembled with Ru/Ti4O7 achieves superior performance and robust operation. The work paves the way for efficient energy conversion devices.

Engineering the Coordination Environment of Ir Single Atoms with Surface Titanium Oxide Amorphization for Superior Chlorine Evolution Reaction

The chlorine evolution reaction (CER) is essential for industrial Cl2 production but strongly relies on the use of dimensionally stable anode (DSA) with high-amount precious Ru/Ir oxide on a Ti substrate. For the purpose of sustainable development, precious metal decrement and performance improvement are highly desirable for the development of CER anodes. Herein, we demonstrate that surface titanium oxide amorphization is crucial to regulate the coordination environment of stabilized Ir single atoms for efficient and durable chlorine evolution of Ti monolithic anodes. Experimental and theoretical results revealed the formation of four-coordinated Ir1O4 and six-coordinated Ir1O6 sites on amorphous and crystalline titanium oxides, respectively. Interestingly, the Ir1O4 sites exhibited a superior CER performance, with a mass activity about 10 and 500 times those of the Ir1O6 counterpart and DSA, respectively. Moreover, the Ir1O4 anode displayed excellent durability for 200 h, far longer than that of its Ir1O6 counterpart (2 h). Mechanism studies showed that the unsaturated Ir in Ir1O4 was the active center for chlorine evolution, which was changed to the top-coordinated O in Ir1O6. This change of active sites greatly affected the adsorption energy of Cl species, thus accounting for their different CER activity. More importantly, the amorphous structure and restrained water dissociation of Ir1O4 synergistically prevent oxygen permeation across the Ti substrate, contributing to its long-term CER stability. This study sheds light on the importance of single-atom coordination structures in the reactivity of catalysts and offers a facile strategy to prepare highly active single-atom CER anodes via surface titanium oxide amorphization.

Superexchange-stabilized long-distance Cu sites in rock-salt-ordered double perovskite oxides for CO2 electromethanation

Cu-oxide-based catalysts are promising for CO2 electroreduction (CO2RR) to CH4, but suffer from inevitable reduction (to metallic Cu) and uncontrollable structural collapse. Here we report Cu-based rock-salt-ordered double perovskite oxides with superexchange-stabilized long-distance Cu sites for efficient and stable CO2-to-CH4 conversion. For the proof-of-concept catalyst of Sr2CuWO6, its corner-linked CuO6 and WO6 octahedral motifs alternate in all three crystallographic dimensions, creating sufficiently long Cu-Cu distances (at least 5.4 Å) and introducing marked superexchange interaction mainly manifested by O-anion-mediated electron transfer (from Cu to W sites). In CO2RR, the Sr2CuWO6 exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH4, together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO3. Moreover, the Sr2CuWO6 is the most effective Cu-based-perovskite catalyst for CO2 methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm-2 for CH4. Our experiments and theoretical calculations highlight the long Cu-Cu distances promoting *CO hydrogenation and the superexchange interaction stabilizing Cu sites as responsible for the superb performance.

Spin Polarization: A New Frontier in Efficient Photocatalysis for Environmental Purification and Energy Conversion

As a promising strategy to improve photocatalytic efficiency, spin polarization has attracted enormous attention in recent years, which could be involved in various steps of photoreaction. The Pauli repulsion principle and the spin selection rule dictate that the behavior of two electrons in a spatial eigenstate is based on their spin states, and this fact opens up a new avenue for manipulating photocatalytic efficiency. In this review, recent advances in modulating the photocatalytic activity with spin polarization are systematically summarized. Fundamental insights into the influence of spin-polarization effects on photon absorption, carrier separation, and migration, and the behaviors of reaction-related substances from the photon uptake to reactant desorption are highlighted and discussed in detail, and various photocatalytic applications for environmental purification and energy conversion are presented. This review is expected to deliver a timely overview of the recent developments in spin-polarization-modulated photocatalysis for environmental purification and energy conversion in terms of their practical applications.

A motif for B/O-site modulation in LaFeO3 towards boosted oxygen evolution

Here, a series of transition metal (Ni) doped iron-based perovskite oxides LaFe1-xNixO3-δ (x = 0, 0.25, 0.5, 0.75, 1) were prepared, and then the perovskite oxide with the optimized nickel-iron ratio was doped with non-metallic elements (N). Experimental and theoretical investigations reveal that the co-doping breaks the traditional linear constraint relationship (GOOH - GOH = 3.2 eV) and the theoretical overvoltage is reduced from 0.64 V (LaFeO3-δ) to 0.44 V (LaFe0.5Ni0.5O3-δ/N). Specifically, Ni-doping can accelerate electron transfer and improve the conductivity. Moreover, N-doping can reduce the adsorption energy of *OH/*O and enhance the adsorption energy of *OOH. We demonstrated that the optimized cation and anion co-doped LaFe0.5Ni0.5O3-δ/N perovskite oxide exhibits an excellent OER performance, with a low overpotential of 270.6 mV at 10 mA cm-2 and a small Tafel slope of 65 mV dec-1 in 1 M KOH solution, markedly exceeding that of the parent perovskite oxide LaFeO3-δ (300.9 mV) and commercial IrO2 (289.1 mV). It also delivers decent durability with no significant degradation after a 35 h stability test. This work reveals the internal mechanism of perovskite oxide by doping cation and anion for water oxidation, which broadens the idea for the rational design of new perovskite-based sustainable energy catalysts.

Improving the electrocatalytic hydrogen evolution reaction through a magnetic field and hydrogen peroxide production co-assisted Ni/Fe3O4@poly(3,4-ethylene-dioxythiophene)/Ni electrode

The production of high-purity hydrogen using surplus electrical energy and abundant water resources has immense potential in mitigating the fossil energy crisis, as hydrogen fuel holds clean, pollution-free, and high-energy characteristics. However, the practical application of large-scale hydrogen production from water faces challenges such as high overpotentials, sluggish dynamics, and limited electrocatalytic lifetime associated with the hydrogen evolution reaction (HER). Here, we fabricated the sandwich structure of a Ni/Fe3O4@poly(3,4-ethylene-dioxythiophene)/Ni (Ni/Fe3O4@PEDOT/Ni) electrode and employed a strong magnet to obtain a magnetic electrode capable of achieving high-activity and durability for HER. Electrochemical analysis reveals that the activated magnetic electrode displays a significantly reduced overpotential and an extended electrocatalytic lifetime of 10 days. Notably, its stability is higher than that of non-magnetic Ni/Fe3O4/Ni and Ni/Fe3O4@PEDOT/Ni electrodes, primarily due to the support from magnetic force and the protective PEDOT layer. Moreover, the minute atomized droplets can form the H2O2 species in a moist environment, facilitating the formation of the NiO layer on the Ni surface, which plays a vital role in boosting catalytic activity. In conclusion, our magnetic electrode strategy, combined with the emergence of the NiO layer, offers valuable insights for the development of advanced HER electrodes.

Large electronegativity differences between adjacent atomic sites activate and stabilize ZnIn2S4 for efficient photocatalytic overall water splitting

Photocatalytic overall water splitting into hydrogen and oxygen is desirable for long-term renewable, sustainable and clean fuel production on earth. Metal sulfides are considered as ideal hydrogen-evolved photocatalysts, but their component homogeneity and typical sulfur instability cause an inert oxygen production, which remains a huge obstacle to overall water-splitting. Here, a distortion-evoked cation-site oxygen doping of ZnIn2S4 (D-O-ZIS) creates significant electronegativity differences between adjacent atomic sites, with S1 sites being electron-rich and S2 sites being electron-deficient in the local structure of S1-S2-O sites. The strong charge redistribution character activates stable oxygen reactions at S2 sites and avoids the common issue of sulfur instability in metal sulfide photocatalysis, while S1 sites favor the adsorption/desorption of hydrogen. Consequently, an overall water-splitting reaction has been realized in D-O-ZIS with a remarkable solar-to-hydrogen conversion efficiency of 0.57%, accompanying a ~ 91% retention rate after 120 h photocatalytic test. In this work, we inspire an universal design from electronegativity differences perspective to activate and stabilize metal sulfide photocatalysts for efficient overall water-splitting.

Spin polarized Fe1-Ti pairs for highly efficient electroreduction nitrate to ammonia

Electrochemical nitrate reduction to ammonia offers an attractive solution to environmental sustainability and clean energy production but suffers from the sluggish *NO hydrogenation with the spin-state transitions. Herein, we report that the manipulation of oxygen vacancies can contrive spin-polarized Fe1-Ti pairs on monolithic titanium electrode that exhibits an attractive NH3 yield rate of 272,000 μg h-1 mgFe-1 and a high NH3 Faradic efficiency of 95.2% at -0.4 V vs. RHE, far superior to the counterpart with spin-depressed Fe1-Ti pairs (51000 μg h-1 mgFe-1) and the mostly reported electrocatalysts. The unpaired spin electrons of Fe and Ti atoms can effectively interact with the key intermediates, facilitating the *NO hydrogenation. Coupling a flow-through electrolyzer with a membrane-based NH3 recovery unit, the simultaneous nitrate reduction and NH3 recovery was realized. This work offers a pioneering strategy for manipulating spin polarization of electrocatalysts within pair sites for nitrate wastewater treatment.

Orderly Nanodendritic Nickel Substitute for Raney Nickel Catalyst Improving Alkali Water Electrolyzer

The development of nonprecious metal catalysts to meet the activity-stability balance at industrial-grade large current densities remains a challenge toward practical alkali-water electrolysis. Here, this work develops an orderly nanodendritic nickel (ND-Ni) catalyst that consists of ultrafine nanograins in chain-like conformation, which shows both excellent activity and robust stability for large current density hydrogen evolution reaction (HER) in alkaline media, superior to currently applied Raney nickel (R-Ni) catalyst in commercial alkali-water electrolyzer (AWE). The ND-Ni catalyst featured by a three-dimensional (3D) interconnecting microporous structure endows with high specific surface area and excellent conductivity and hydrophilicity, which together afford superior charge/mass transport favorable to HER kinetics at high current densities. An actual AWE with ND-Ni catalyst demonstrates durable water splitting with 1.0 A cm-2 at 1.71 V under industrial conditions and renders a record-low power consumption of 3.95 kW h Nm-3 with an energy efficiency close to 90%. The hydrogen price per gallon of gasoline equivalent (GGE) is calculated to be ≈$0.95, which is less than the target of $2.0 per GGE by 2026 from the U.S. Department of Energy. The results suggest the feasibility of ND-Ni substitute for R-Ni catalyst in commercial AWE.

Strategies for improving the stability of perovskite for photocatalysis: A review of recent progress

Photocatalysis is currently a hot research field, which provides promising processes to produce green energy sources and other useful products, thus eventually benefiting carbon emission reduction and leading to a low-carbon future. The development and application of stable and efficient photocatalytic materials is one of the main technical bottlenecks in the field of photocatalysis. Perovskite has excellent performance in the fields of photocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO2RR), organic synthesis and pollutant degradation due to its unique structure, flexibility and resulting excellent photoelectric and catalytic properties. The stability problems caused by perovskite's susceptibility to environmental influences hinder its further application in the field of photocatalysis. Therefore, this paper innovatively summarizes and analyzes the existing methods and strategies to improve the stability of perovskite in the field of photocatalysis. Specifically, (i) component engineering, (ii) morphological control, (iii) hybridization and encapsulation are thought to improve the stability of perovskites while improving photocatalytic efficiency. Finally, the challenges and prospects of perovskite photocatalysts are discussed, which provides constructive thinking for the potential application of perovskite photocatalysts.

Cation-Radius-Controlled Sn-O Bond Length Boosting CO2 Electroreduction over Sn-Based Perovskite Oxides

Despite the intriguing potential shown by Sn-based perovskite oxides in CO2 electroreduction (CO2 RR), the rational optimization of their CO2 RR properties is still lacking. Here we report an effective strategy to promote CO2 -to-HCOOH conversion of Sn-based perovskite oxides by A-site-radius-controlled Sn-O bond lengths. For the proof-of-concept examples of Ba1-x Srx SnO3 , as the A-site cation average radii decrease from 1.61 to 1.44 Å, their Sn-O bonds are precisely shortened from 2.06 to 2.02 Å. Our CO2 RR measurements show that the activity and selectivity of these samples for HCOOH production exhibit volcano-type trends with the Sn-O bond lengths. Among these samples, the Ba0.5 Sr0.5 SnO3 features the optimal activity (753.6 mA ⋅ cm-2 ) and selectivity (90.9 %) for HCOOH, better than those of the reported Sn-based oxides. Such optimized CO2 RR properties could be attributed to favorable merits conferred by the precisely controlled Sn-O bond lengths, e.g., the regulated band center, modulated adsorption/activation of intermediates, and reduced energy barrier for *OCHO formation. This work brings a new avenue for rational design of advanced Sn-based perovskite oxides toward CO2 RR.

Cation Substitution Strategy for Developing Perovskite Oxide with Rich Oxygen Vacancy-Mediated Charge Redistribution Enables Highly Efficient Nitrate Electroreduction to Ammonia

The electrocatalytic nitrate (NO3-) reduction reaction (eNITRR) is a promising method for ammonia synthesis. However, its efficacy is currently limited due to poor selectivity, largely caused by the inherent complexity of the multiple-electron processes involved. To address these issues, oxygen-vacancy-rich LaFe0.9M0.1O3-δ (M = Co, Ni, and Cu) perovskite submicrofibers have been designed from the starting material LaFeO3-δ (LF) by a B-site substitution strategy and used as the eNITRR electrocatalyst. Consequently, the LaFe0.9Cu0.1O3-δ (LF0.9Cu0.1) submicrofibers with a stronger Fe-O hybridization, more oxygen vacancies, and more positive surface potential exhibit a higher ammonia yield rate of 349 ± 15 μg h-1 mg-1cat. and a Faradaic efficiency of 48 ± 2% than LF submicrofibers. The COMSOL Multiphysics simulations demonstrate that the more positive surface of LF0.9Cu0.1 submicrofibers can induce NO3- enrichment and suppress the competing hydrogen evolution reaction. By combining a variety of in situ characterizations and density functional theory calculations, the eNITRR mechanism is revealed, where the first proton-electron coupling step (*NO3 + H+ + e- → *HNO3) is the rate-determining step with a reduced energy barrier of 1.83 eV. This work highlights the positive effect of cation substitution in promoting eNITRR properties of perovskites and provides new insights into the studies of perovskite-type electrocatalytic ammonia synthesis catalysts.

Symmetry or asymmetry: which one is the platform of nitrogen vacancies for alkaline hydrogen evolution

Conventional nitrogen vacancies with a symmetric coordination of metal cations (i.e., M1-Nv-M1) play a crucial role in tuning the local environment of the metal sites in metal nitrides and improving their electrochemical activity in the hydrogen evolution reaction (HER). However, the symmetric Nv sites, which feature a uniform charge distribution on adjacent metal sites, suffer from sluggish water dissociation kinetics and a poor capability for hydrogen desorption. Here, we fabricated Cr-doped and Nv-rich Co4N nanorods grown on a Ni foam (Cr-Co4N-Nv/NF) with asymmetric Cr-Nv-Co sites to effectively catalyze hydrogen evolution under alkaline conditions, with a low overpotential of 33 mV at a current density of 10 mA cm-2 and a small Tafel slope of 37 mV dec-1. The experimental characterizations and theoretical simulations collectively reveal that the construction of asymmetric Cr-Nv-Co sites gives rise to the upshift of the d-band center, thus promoting water adsorption and activation. Moreover, asymmetric Nv sites allow a balance between hydrogen adsorption and desorption, which avoids the limited desorption process over the symmetric Co-Nv-Co sites.

Effective Hydrogen Production from Alkaline and Natural Seawater using WO3-x@CdS1-x Nanocomposite-Based Electrocatalysts

Offshore hydrogen production through water electrolysis presents significant technical and economic challenges. Achieving an efficient hydrogen evolution reaction (HER) in alkaline and natural seawater environments remains daunting due to the sluggish kinetics of water dissociation. To address this issue, we synthesized electrocatalytic WO3-x@CdS1-x nanocomposites (WCSNCs) using ultrasonic-assisted laser irradiation. The synthesized WCSNCs with varying CdS contents were thoroughly characterized to investigate their structural, morphological, and electrochemical properties. Among the samples tested, the WCSNCs with 20 wt % CdS1-x in WO3-x (Wx@Sx-20%) exhibited superior electrocatalytic performance for hydrogen evolution in a 1 M KOH solution. Specifically, the Wx@Sx-20% catalyst demonstrated an overpotential of 0.191 V at a current density of -10 mA/cm2 and a Tafel slope of 61.9 mV/dec. The Wx@Sx-20% catalysts demonstrated outstanding stability and durability, maintaining their performance after 24 h and up to 1000 CV cycles. Notably, when subjected to natural seawater electrolysis, the Wx@Sx-20% catalysts outperformed in terms of electrocatalytic HER activity and stability. The remarkable performance enhancement of the prepared electrocatalyst can be attributed to the combined effect of sulfur vacancies in CdS1-x and oxygen vacancies in WO3-x. These vacancies promote the electrochemically active surface area, enhance the rate of charge separation and transfer, increase the number of electrocatalytic active sites, and accelerate the HER process in alkaline and natural seawater environments.

Dynamic active-site induced by host-guest interactions boost the Fenton-like reaction for organic wastewater treatment

In heterogeneous catalysis, uncovering the dynamic evolution of active sites in the working conditions is crucial to realizing increased activity and enhanced stability of catalyst in Fenton-like activation. Herein, we capture the dynamic changes in the unit cell of Co/La-SrTiO₃ catalyst during the exemplary peroxymonosulfate activation process using X-ray absorption spectroscopy and in situ Raman spectroscopy, revealing the substrate tuned its structural evolution, which is the reversible stretching vibration of O-Sr-O and Co/Ti-O bonds in different orientations. This process effectively promotes the generation of key SO₅* intermediates, which is beneficial to the formation of ¹O₂ and SO₄^•- from persulfate on the Co active site. Density functional theory and X-ray absorption spectroscopy show that the optimized structural distortion enhanced the metal-oxygen bond strength by tuning the e_g orbitals and increased the number of transferred electrons to peroxymonosulfate by about 3-fold, achieving excellent efficiency and stability in removing organic pollutants.