Active oxygen species mediate the iron-promoting electrocatalysis of oxygen evolution reaction on metal oxyhydroxides

Enhanced catalytic ozonation via FeBi bimetallic catalyst: Unveiling the role of zero-valent Bi as an oxygen vacancy-mediated electron reservoir

A series of bimetallic carbon catalysts (FeM@C, M = Bi, Ce, Co, Ni, Mn) were synthesized via pyrolysis of metal-organic framework (MOF) precursors, among which FeBi@C exhibits exceptional catalytic ozonation performance, achieving 90.73 % oxalic acid removal within 30 min and retaining 84 % of its initial activity over eight consecutive cycles. Advanced characterizations, including EPR, and in-situ Raman spectroscopy, revealed that oxygen vacancies (OV) serve as active sites for ozone adsorption, leading to the formation of reactive oxygen species (ROS) and ≡ Fe-O-O- peroxo intermediates. The post-reaction XPS analysis indicated significant shifts in binding energies and changes in the proportions of oxygen species, revealing the unique Fe-Bi synergy. The Fe2p spectra showed a decrease in Fe2+ content and a negative shift in binding energy, indicating an active Fe2+/Fe3+ redox cycle. The Bi4f spectra confirmed the presence of zero-valent Bi, which acts as an "electron reservoir", continuously donating electrons to enhance Fe2+/Fe3+ redox cycle and promote ozone activation. This unique mechanism, where zero-valent Bi sustains the electron transfer cycle, significantly enhances both the catalytic efficiency and long-term stability of the FeBi@C system, distinguishing it from conventional bimetallic catalysts. This work provides a novel strategy for designing high-performance catalysts for environmental remediation.

Built-In Electric Field in Freestanding Hydroxide/Sulfide Heterostructures for Industrially Relevant Oxygen Evolution

Alkaline water electrolysis (AWE), as a premier technology to massively produce green hydrogen, hinges on outstanding oxygen evolution reaction (OER) electrodes with high activity and robust stability under high current densities. However, it is often challenged by issues such as catalytic layer shedding, ion dissolution, and inefficient bubble desorption. Herein, a scalable corrosion-electrodeposition method is presented to synthesize nickel-iron layered double hydroxide (NiFe-LDH)/Ni3S2 heterostructures on nickel mesh, tailored to meet the stringent requirements of industrial AWE. The study underscores the critical role of the built-in electric field (BEF) in optimizing electronic properties, curtailing Fe leaching, and enhancing mass transfer. The resultant NiFe-LDH/Ni3S2 heterostructure manifests remarkable OER performance, with ultra-low overpotentials of 202 mV at 10 mA cm-2 and 290 mV at 800 mA cm-2 in 1.0 m KOH at 25 °C, alongside superior steady-state stability and resistance to reverse current under fluctuating conditions. Furthermore, the performance is further validated in an alkaline electrolyzer, achieving a large current density of 800 mA cm-2 at a cell voltage of 1.908 V, while maintaining excellent stability. This work offers a blueprint for the design of efficient OER electrodes for industrially relevant AWE applications.

Self-replenishing Ni-rich stainless-steel electrode toward oxygen evolution reaction at ampere-level

In the past few decades, tremendous attention has been devoted to enhancing the activity of oxygen evolution reaction (OER) catalysts for hydrogen production, while the cost and long-term stability of catalysts, which can play an even more important role in industrialization, have been much less emphasized. Herein, we engineered an OER electrode from abundant stainless steel (SS) via facile approaches, and the obtained electrode consists of a Ni-rich oxide surface layer with a Fe-rich metal substrate. An outstanding activity was observed with an overpotential of 316 mV at 100 mA cm-2 in 1 M KOH electrolyte. Additionally, an electrode self-replenishing concept is proposed in which a Ni-rich catalyst layer can be regenerated from a metallic substrate due to the difference in diffusion and dissolution rates of metal oxides/hydroxides, and this regeneration is validated by various characterizations. A recorded degradation rate of 0.012 was observed at 1000 mA cm-2 for 1000 h. The facile engineering of OER electrodes from SS combined with the self-replenishing catalyst can potentially address the cost, activity, and long-term stability barriers.

Self-Supported NiCo2S4@Ce-NiFe LDH/CeO2 Nanoarrays for Electrochemical Water Splitting

The design of high-performance OER catalysts is crucial for efficient electrochemical water splitting (EWS). Herein, a NiCo2S4@Ce-NiFe LDH/CeO2 heterostructure nanoarray electrocatalyst with abundant oxygen defect sites is reported. The introduction of Ce species activates the lattice oxygen in the oxyhydroxides, inducing the transformation of the catalytic mechanism toward the lattice oxygen oxidation mechanism (LOM) pathway, bypassing the thermodynamic limitation of the adsorbate evolution mechanism (AEM), and strengthening the intrinsic activity of the material. Moreover, the reversible transitions between different oxidation states of Ce species and the high oxygen storage capacity of CeO2 regulate the adsorption behavior of the reaction intermediates, allowing it to be easier for the material to enrich the oxygen-containing intermediates, thereby improving the adsorption kinetics. Accordingly, NiCo2S4@Ce-NiFe LDH/CeO2 exhibits remarkable OER performance (η50 = 226 mV, η100 = 244 mV) and brilliant stability. Additionally, the presence of the CeO2 protective layer inhibits the impact of Cl- and other pollutants in seawater, which enables NiCo2S4@Ce-NiFe LDH/CeO2 to perform satisfactorily in seawater electrolysis, as well. This study offers a fresh perspective on the design of defect-rich OER catalysts.

Enhancing Oxygen Evolution Electrocatalysis in Heazlewoodite: Unveiling the Critical Role of Entropy Levels and Surface Reconstruction

Entropy engineering has proven effective in enhancing catalyst electrochemical properties, particularly for the oxygen evolution reaction (OER). Challenges persist, however, in modulating entropy and understanding the dynamic reconfiguration of high-entropy sulfides during OER. In this study, an innovative in situ corrosion method is introduced to convert low-valent nickel on a nickel foam substrate into high-entropy heazlewoodite (HES/NF), significantly boosting OER performance. By synthesizing a series of low-, medium-, and high-entropy heazlewoodites, the intrinsic factors influence catalyst surface evolution and electrocatalytic activity is systematically explored. Employing a combination of in situ and ex situ characterization techniques, it is observed that HES/NF dynamically transforms into a stable hydroxide oxide (MOOH)-sulfide composite under OER conditions. This transition, coupled with lattice distortion, optimizes the electrostatic potential distribution, ensuring superior catalytic activity and preventing surface sulfide deactivation through the formation of stable HES-MOOH species. This synergy enables HES/NF to achieve remarkably low overpotentials: 172.0 mV at 100.0 mA cm-2 and 229.0 mV at an extreme current density of 300.0 mA cm-2. When paired with a Pt/C cathode, HES/NF exhibits rapid kinetics, outstanding stability, and exceptional water-splitting performance. The scalable, cost-effective approach paves the way for advanced electrocatalyst design, promising breakthroughs in energy storage and conversion technologies.

Fe-Doped Ni-Phytate/Carbon Nanotube Hybrids Integrating Activated Lattice Oxygen Participation and Enhanced Photothermal Effect for Highly Efficient Oxygen Evolution Reaction Electrocatalyst

Developing highly efficient oxygen evolution reaction (OER) electrocatalysts is critical for hydrogen production through electrocatalytic water splitting, yet it remains a significant challenge. In this study, a novel OER electrocatalyst, Fe-doped Ni-phytate supported on carbon nanotubes (NiFe-phy/CNT), which simultaneously follows lattice oxygen mechanism (LOM) and exhibits a photothermal effect, is synthesized through a facile and scalable co-precipitation method. Experimental results combined with theoretical calculations indicate that introducing Fe can facilitate the structural reconstruction of NiFe-phy/CNT to form highly active NiFe oxyhydroxides, switch OER pathway to LOM from the adsorbate evolution mechanism, and reinforce the photothermal effect to counterbalance the enthalpy change during OER process while reducing its activation energy. Therefore, under near-infrared light irradiation, NiFe-phy/CNT demonstrates exceptional OER activity, featuring low overpotentials of 237, 275, and 286 mV at 100, 500, and 1000 mA cm-2, respectively. Moreover, this electrocatalyst demonstrates the capability of large-scale synthesis and can be stored for over 120 days with a negligible decrease in activity. This work presents a novel conceptual approach to integrate lattice oxygen redox chemistry with photothermal effect for designing highly efficient OER electrocatalysts.

Strategies for Enhancing Stability in Electrochemical CO2 Reduction

The electrochemical CO2 reduction reaction (CO2RR) holds significant promise as a sustainable approach to address global energy challenges and reduce carbon emissions. However, achieving long-term stability in terms of catalytic performance remains a critical hurdle for large-scale commercial deployment. This mini-review provides a comprehensive exploration of the key factors influencing CO2RR stability, encompassing catalyst design, electrode architecture, electrolyzer optimization, and operational conditions. We examine how catalyst degradation occurs through mechanisms such as valence changes, elemental dissolution, structural reconfiguration, and active site poisoning and propose targeted strategies for improvement, including doping, alloying, and substrate engineering. Additionally, advancements in electrode design, such as structural modifications and membrane enhancements, are highlighted for their role in improving stability. Operational parameters such as temperature, pressure, and electrolyte composition also play crucial roles in extending the lifespan of the reaction. By addressing these diverse factors, this review aims to offer a deeper understanding of the determinants of long-term stability in the CO2RR, laying the groundwork for the development of robust, scalable technologies for efficient carbon dioxide conversion.

An imidazo-pyridin derivative as fluorescent probe for the peroxynitrite detection in pulmonary permissive hypercapnia

The physiological and pathological processes in lungs indicated that ONOO- acted as an informative indicator for pulmonary functioning status with the corresponding dynamics, especially in permissive hypercapnia. Herein, for the peroxynitrite (ONOO-) detection and imaging in living lung cells, an imidazo-pyridin derived fluorescent probe IDPD-ONOO was developed. IDPD-ONOO recognized ONOO- to exhibit a corresponding fluorescence response at 490 nm with the excitation wavelength at 355 nm. The advantages of the developed probe included practical linear range (0-100 μM), high sensitivity (Limit of Detection 0.005 μM), rapid response (within 15 min), pH tolerance (7.0-9.0), high selectivity, and low cyto-toxicity. Furthermore, IDPD-ONOO achieved the pulmonary intracellular imaging of both the exogenous and endogenous ONOO- level, which was meaningful for the research on the pulmonary physiological and pathological mechanism with optimized optical implements.

Machine learning assisted Co3O4/NiO popsicle sticks-infused electrospun nanofibers for efficient oxygen evolution reaction

Wide range of noble metal free bimetallic and trimetallic based electrocatalysts have been synthesized to develop efficient oxygen evolution reaction (OER) systems to-date, however, to determine which metal part of bimetallic and trimetallic electrocatalysts plays a significant role in controlling OER efficacy remains very challenging. To address this issue, herein we have employed machine learning (ML) for the first time to determine OER efficacy controlling metal element, thus leading to the development of an optimized bimetallic electrocatalyst. Briefly, we have designed a novel, simple ML optimized sustainable OER electrocatalyst based on Co3O4/NiO popsicle sticks (CNPS) infused polyaniline/cellulose acetate (a biopolymer) (PNCA) electrospun nanofibers supported on nickel foam (NF). ML optimized CNPS infused PNCA (CNPS@PNCA) electrode offers maximum and homogenous exposition of active sites and shows high OER activity by exhibiting low onset potential (1.41 V vs. RHE), overpotential (237 mV at 10 mA cm-2) and Tafel slope of 62.1 mV dec-1. Additionally, it shows a better stability of more than 100 h and is consistent with the reported literature.

Tailoring Octahedron-Tetrahedron Synergism in Spinel Catalysts for Acidic Water Electrolysis

The instability issues of oxide-based electrocatalysts during the oxygen evolution reaction (OER) under acidic conditions, caused by the oxidation and dissolution of the catalysts along with the current-capacitance effect, constrain their application in proton exchange membrane water electrolysis (PEMWE). To address these challenges, we tailored the spinel structure of Co3O4 and exploited the synergism between the tetrahedron and octahedron sites by partially substituting Co with Ni and Ru (denoted as NiRuCoOx), respectively. Such a catalyst design creates a Ru-O-Ni electronic coupling effect, facilitating a direct dioxygen radical-coupled OER pathway. Density-functional theory (DFT) calculations and in situ Raman spectroscopy results confirm that Ru is the active site in the diatomic oxygen mechanism while Ni stabilizes lattice oxygen and the Ru-O bonding. The designed NiRuCoOx catalyst exhibits an exceptionally low overpotential of 166 mV to achieve a current density of 10 mA cm-2. Moreover, when serving as the anode in PEMWE, the NiRuCoOx requires 1.72 V to reach a current density of 3A cm-2, meeting the 2026 target set by the U.S. Department of Energy (DOE: 1.8 V@3A cm-2). The PEMWE device can operate stably for more than 1500 h with a significantly reduced performance decay rate of 0.025 mV h-1 compared to commercial RuO2 (2.13 mV h-1). This work provides an efficient method for tailoring the octahedron-tetrahedron sites of spinel Co3O4, which significantly improves the activity and stability of PEMWE.

A 17.73 % Solar-To-Hydrogen Efficiency with Durably Active Catalyst in Stable Photovoltaic-Electrolysis Seawater System

Developing durably active catalysts to tackle harsh voltage polarization and seawater corrosion is pivotal for efficient solar-to-hydrogen (STH) conversion, yet remains a challenge. We report a durably active catalyst of NiCr-layered double hydroxide (RuldsNiCr-LDH) with highly exposed Ni-O-Ru units, in which low-loading Ru (0.32 wt %) is locked precisely at defect lattice site (Rulds) by Ni and Cr. The Cr site electron equilibrium reservoir and Cl- repulsion by intercalated CO3 2- ensure the highly durable activity of Ni-O-Ru units. The RuldsNiCr-LDH‖RuldsNiCr-LDH electrolyzer based on anion exchange membrane water electrolysis (AEM-WE) shows ultrastable seawater electrolysis at 1000 mA cm-2. Employing RuldsNiCr-LDH both as anode and cathode, a photovoltaic-electrolysis seawater system achieves a 17.73 % STH efficiency, corresponding photovoltaic-to-hydrogen (PVTH) efficiency is 72.37 %. Further, we elucidate the dynamic evolutionary mechanism involving the interfacial water dissociation-oxidation, establishing the correlation between the dynamic behavior of interfacial water with the kinetics, activity of RuldsNiCr-LDH catalytic water electrolysis. Our work is a breakthrough step for achieving economically scalable production of green hydrogen.

Leveraging Iron in the Electrolyte to Improve Oxygen Evolution Reaction Performance: Fundamentals, Strategies, and Perspectives

Electrochemical water splitting is a pivotal technology for storing intermittent electricity from renewable sources into hydrogen fuel. However, its overall energy efficiency is impeded by the sluggish oxygen evolution reaction (OER) at the anode. In the quest to design high-performance anode catalysts for driving the OER under non-acidic conditions, iron (Fe) has emerged as a crucial element. Although the profound impact of adventitious electrolyte Fen+ species on OER catalysis had been reported forty years ago, recent interest in tailoring the electrode-electrolyte interface has spurred studies on the controlled introduction of Fe ions into the electrolyte to improve OER performance. During the catalytic process, scenarios where the rate of Fen+ deposition on a specific host material outruns that of dissolution pave the way for establishing highly efficient and dynamically stable electrochemical interfaces for long-term steady operation. This review systematically summarizes recent endeavors devoted to elucidating the behaviors of in situ Fe(aq.) incorporation, the role of incorporated Fe sites in the OER, and critical factors influencing the interplay between the electrode surface and Fe ions in the electrolyte environment. Finally, unexplored issues related to comprehensively understanding and leveraging the dynamic exchange of Fen+ at the interface for improved OER catalysis are summarized.

Modulating the Oxygen Evolution Reaction of Single-Crystal Cobalt Carbonate Hydroxide via Surface Fe Doping and Facet Dependence

The oxygen evolution reaction (OER) is a critical half-reaction in water splitting and metal-air cells. The sensitivity of the OER to the composition and structure of the electrocatalyst presents a significant challenge in elucidating the structure-property relationship. In this study, highly stable single-crystal cobalt carbonate hydroxide [Co2(OH)2CO3, CoCH] was used as a model to investigate the correlations among structure, composition, and reactivity. Single-crystal CoCH nanowires (denoted as CoCH NWs) and Fe-doped CoCH nanowires (denoted as Fe-CoCH NWs) with an exposed (210) facet and Fe-doped CoCH nanosheets (denoted as Fe-CoCH NSs) with an exposed (2-13) facet were synthesized using electrochemical and one-step hydrothermal strategies, respectively. Their OER activity decreased in the following order: Fe-CoCH NWs > Fe-CoCH NSs > CoCH NWs. Theoretical investigation suggested that the doped Fe sites serve as active sites, and the crystal-facet dependence can finely adjust the 3d configuration of Fe sites, resulting in the optimal adsorption strengths and energy barriers for potential-determining steps on the (210) facet of CoCH. This renders the as-prepared Fe-CoCH NWs as some of the most promising Co-based OER catalysts.

Synergistic Atomic Environment Optimization of Nickel-Iron Dual Sites by Co Doping and Cr Vacancy for Electrocatalytic Oxygen Evolution

The dual-site synergistic catalytic mechanism on NiFeOOH suggests weak adsorption of Ni sites and strong adsorption of Fe sites limited its activity toward alkaline oxygen evolution reaction (OER). Large-scale density functional theory (DFT) calculations confirm that Co doping can increase Ni adsorption, while the metal vacancy can reduce Fe adsorption. The combined two factors can further modulate the atomic environment and optimize the free energy toward oxygen-containing intermediates, thus enhancing the OER activity. Accordingly, we used Co doping and Cr vacancies to fabricate an amorphous catalyst of VCr,Co-NiFeOOH. It provides an OER overpotential of 239 mV at 100 mA cm-2 and high stability over 500 h at 500 mA cm-2 with a ∼98% potential retention. The resulting water electrolyzer based on an anion exchange membrane (AEM) exhibits a remarkable performance of 1 A cm-2 at 1.68 V in 1 M KOH. XPS, soft-XAS, and XANES combined with Bader charge analysis results reveal that the regulation of the local microenvironment can increase the valence state of Ni by Co doping, thus improving the adsorption energy on Ni sites. The Cr vacancy can alleviate the strong adsorption on Fe sites. DFT calculations confirm that the synergistic effect of Co doping and Cr vacancies can redistribute the charge on the Ni/Fe sites, optimize the d-band center of Ni and Fe, and endow the catalyst with Ni-Fe dual sites to reduce the energy barrier of the OER rate-determining step.

Designing ternary Co-Ni-Fe layered double hydroxides within a novel 3D cross-flower framework for efficient catalytic performance in oxygen evolution reaction

In this study, we synthesized novel three-dimensional (3D) cross-flowered Co-Ni metal-organic framework (Co-Ni-MOF) precursors using the chemical precipitation method. Subsequently, we obtained Co-Ni-Fe layered double hydroxides (Co-Ni-Fe-LDHs) through an ion exchange strategy, which preserved their original morphology while consisting of ultrathin layered hydroxide nanosheets. The interlayer spacing of the LDH lamellar structure was finely tuned by varying the ratios of Co to Ni. The results demonstrated that Co-Ni-Fe LDHs, characterized by a unique three-dimensional cross-shaped structure and an optimal composition ratio of Co2+:Ni2+ = 2:1, exhibited increased interlayer spacing. This structural characteristic contributed to their excellent electrochemical performance, positioning them as optimal electrode materials for catalytic oxygen evolution reactions (OER). Our observations revealed that Co-Ni-Fe-LDHs exhibited remarkable OER activity, characterized by a low Tafel slope of 41.82 mV dec-1, a low overpotential of 322 mV at a current density of 10 mA cm-2, and outstanding stability over a 48-hour period. In-situ Raman spectroscopy results indicated that the active site of the composite was γ-CoOOH. Additionally, the room temperature stirring and standing strategy employed in this study is easier to scale up and yields a higher quantity of reaction products compared to traditional high-temperature and high-pressure conditions. This investigation provides novel insights into the design and fabrication of Co-Ni-Fe-LDHs catalyst with 3D cross-flower structures, demonstrating enhanced electrocatalytic activity and commendable stability. These findings suggest promising applications in the field of electrolyzed water.

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction

The catalysts were always undergoing continuous amorphization and dissolution of active structure in operating condition, hindering the compatibility between stability and activity for oxygen evolution reaction (OER). Herein, we propose the selective adsorption of leached NO3 - to strengthen the crystallinity and activity of surface reconstructed layer with amorphous and crystalline (a-c) heterojunction. Taking a-c Ni doped Fe2O(OH)3NO3 ⋅ H2O (Ni-FeNH) as a model precatalyst, we uncover that the leached NO3 - are readily adsorbs on the crystalline phase in the formed a-c Fe(Ni)OOHduring OER, lowering the disorder degree and further activating Ni and Fe ion of the crystalline Fe(Ni)OOH on a-c heterojunctions. Accordingly, Ni-FeNH deliver a low overpotential of 303 mV and high durability of 500 hours at 500 mA cm-2 for OER. Particularly, constructing industrial water electrolysis equipment exhibits high stability of 100 hours under a high operating current of 8000 mA.

Advances in Stability of NiFe-Based Anodes toward Oxygen Evolution Reaction for Alkaline Water Electrolysis

Alkaline electrolysis plays a crucial role in sustainable energy solutions by utilizing electrolytic cells to produce hydrogen gas, providing a clean and efficient method for energy storage and conversion. Efficient, stable, and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential to facilitate alkaline water electrolysis on a commercial scale. Nickel-iron-based (NiFe-based) transition metal electrocatalysts are considered the most promising non-precious metal catalysts for alkaline OER due to their low cost, abundance, and tunable catalytic properties. Nevertheless, the majority of existing NiFe-based catalysts suffer from limited activity and poor stability, posing a significant challenge in meeting industrial applications. This also highlights a common situation where the emphasis on material activity receives significant attention, while the equally critical stability aspect is often underemphasized. Initiating with a comprehensive exploration of the stability of NiFe-based OER materials, this article first summarizes the debate surrounding the determination of active sites in NiFe-based OER electrocatalysts. Subsequently, the degradation mechanisms of recently reported NiFe-based electrocatalysts are outlined, encompassing assessments of both chemical and mechanical endurance, along with essential approaches for enhancing their stability. Finally, suggestions are put forth regarding the essential considerations for the design of NiFe-based OER electrocatalysts, with a focus on heightened stability.

Structure-Activity Relationships in Oxygen Electrocatalysis

Oxygen electrocatalysis, as the pivotal circle of many green energy technologies, sets off a worldwide research boom in full swing, while its large kinetic obstacles require remarkable catalysts to break through. Here, based on summarizing reaction mechanisms and in situ characterizations, the structure-activity relationships of oxygen electrocatalysts are emphatically overviewed, including the influence of geometric morphology and chemical structures on the electrocatalytic performances. Subsequently, experimental/theoretical research is combined with device applications to comprehensively summarize the cutting-edge oxygen electrocatalysts according to various material categories. Finally, future challenges are forecasted from the perspective of catalyst development and device applications, favoring researchers to promote the industrialization of oxygen electrocatalysis at an early date.

Revealing Enhanced Active Oxygen Formation by Incorporating Chromium into Nickel Hydroxide Nanosheets for Improved Oxygen Evolution Reaction

Nickel-based oxyhydroxides have emerged as promising catalysts for the oxygen evolution reaction (OER) among Earth-abundant metals. While the incorporation of foreign elements is recognized to enhance catalytic activity, the origin of this enhancement is still debated. We synthesize and examine Ni hydroxide nanosheets, both with and without Cr doping, to elucidate the underlying enhancements. Operando UV-vis and Raman spectroscopy are employed to unravel the behavior of the catalysts. The Cr doping facilitates the oxidation of Ni, resulting in the generation of active oxygen species. The enriched active oxygen species improves OER performance through a lattice oxygen-mediated pathway in Fe-free KOH, and further contribute to the creation and increased activity of FeOxHy sites in the presence of Fe impurities. This work provides a mechanistic understanding of the performance enhancement in Ni-based catalysts through Cr doping and suggests a strategy for the design of more efficient catalysts in the future.

Surface Catalytic Repair for the Efficient Regeneration of Spent Layered Oxide Cathodes

Direct recycling is considered to be the next-generation recycling technology for spent lithium-ion batteries due to its potential economic benefits and environmental friendliness. For the spent layered oxide cathode materials, an irreversible phase transition to a rock-salt structure near the particle surface impedes the reintercalation of lithium ions, thereby hindering the lithium compensation process from fully restoring composition defects and repairing failed structures. We introduced a transition-metal hydroxide precursor, utilizing its surface catalytic activity produced during annealing to convert the rock-salt structure into a layered structure that provides fast migration pathways for lithium ions. The material repair and synthesis processes share the same heating program, enabling the spent cathode and added precursor to undergo a topological transformation to form the targeted layered oxide. This regenerated material exhibits a performance superior to that of commercial cathodes and maintains 88.4% of its initial capacity after 1000 cycles in a 1.3 Ah pouch cell. Techno-economic analysis highlights the environmental and economic advantages of surface catalytic repair over pyrometallurgical and hydrometallurgical methods, indicating its potential for practical application.

Rainwater-borne H2O2 accelerates roxarsone degradation and reduces bioavailability of arsenic in paddy rice soils

Contamination of rice by arsenic represents a significant human health risk. Roxarsone -bearing poultry manure is a major pollution source of arsenic to paddy soils. A mesocosm experiment plus a laboratory experiment was conducted to reveal the role of rainwater-borne H2O2 in the degradation of roxarsone in paddy rice soils. While roxarsone could be degraded via chemical oxidation by Fenton reaction-derived hydroxyl radical, microbially mediated decomposition was the major mechanism. The input of H2O2 into the paddy soils created a higher redox potential, which favored certain roxarsone-degrading and As(III)-oxidizing bacterial strains and disfavored certain As(V)-reducing bacterial strains. This was likely to be responsible for the enhanced roxarsone degradation and transformation of As(III) to As(V). Fenton-like reaction also tended to enhance the formation of Fe plaque on the root surface, which acted as a filter to retain As. The dominance of As(V) in porewater, combined with the filtering effect of Fe plaque significantly reduced the uptake of inorganic As by the rice plants and consequently its accumulation in the rice grains. The findings have implications for developing management strategies to minimize the negative impacts from the application of roxarsone-containing manure for fertilization of paddy rice soils.

Constructing heterogeneous interface between Co3O4 and RuO2 with enhanced electronic regulation for efficient oxygen evolution reaction at large current density

Exploring effective strategies for developing new high-efficiency catalysts for water splitting is essential for advancing hydrogen energy technology. Herein, Co3O4/RuO2 heterojunction interface is construct through ion exchange reaction and pyrolysis. The as-synthesized Co3O4/RuO2-4 exhibits outstanding oxygen evolution reaction (OER) activity at the current density of 100 mA cm-2 with a low overpotential of 276 mV, and remarkable stability (maintaining activity for 60 h at 100 mA cm-2). Experimental results and theoretical calculations reveal that the electrons around the heterogeneous interface transferred from RuO2 to Co3O4, resulting in electron redistribution and optimization of energy barriers for OER intermediates. This unique composite catalyst structure offers a new potential for designing efficient oxygen electrocatalysts at large current density.

Iron Integration in Nickel Hydroxide Matrix vs Surface for Oxygen-Evolution Reaction: Where the Nernst Equation Does Not Work

This study focuses on the oxygen-evolution reaction (OER) activity comparison between two forms of NiFe (hydr)oxides: compound 1, where Fe ions are applied on the surface of nickel (hydr)oxide, and compound 2, with Fe ions incorporated into the structural matrix of nickel (hydr)oxide. The observed exponential link between Coulombic energy and the total charge of the system points to a direct proportionality between the potential and the concentration of oxidized nickel ions (e.g., V ∝ [oxidized Ni]), diverging from the logarithmic relationship outlined in the Nernst equation or its modifications, which is not evident in this case. Initial visible spectroscopy indicates a notable trend toward oxidation. As, during the oxidation, more Ni is oxidized, a repulsion effect develops, diminishing the likelihood of further oxidation, and a distinct linear correlation emerges between the quantity of oxidized Ni(II) and the applied potentials.

Interfacial Interaction in NiFe LDH/NiS2/VS2 for Enhanced Electrocatalytic Water Splitting

A bifunctional electrocatalyst with high efficiency and low costs for overall water splitting is critical to achieving a green hydrogen economy and coping with the energy crisis. However, developing robust electrocatalysts still faces huge challenges, owing to unsatisfactory electron transfer and inherent activity. Herein, NiFe LDH/NiS2/VS2 heterojunctions have been designed as freestanding bifunctional electrocatalysts to split water, exhibiting enhanced electron transfer and abundant catalytic sites. The optimum NiFe LDH/NiS2/VS2 electrocatalyst exhibits a small overpotential of 380 mV at 10 mA cm-2 for overall water splitting and superior electrocatalytic performance in both hydrogen and oxygen evolution reactions (HER/OER). Specifically, the electrocatalyst requires overpotentials of 76 and 286 mV at 10 mA cm-2 for HER and OER, respectively, in alkaline electrolytes, which originate from the synergistic interaction among the facilitated electron transfer and increasingly exposed active sites due to the modulation of interfaces and construction of heterojunctions.