Operando Identification of the Dynamic Behavior of Oxygen Vacancy-Rich Co3O4 for Oxygen Evolution Reaction

Porous-dual-shell structure and heterojunction Co3O4@NiCo2O4 accelerating polysulfides conversion for all-solid-state lithium sulfur batteries

All-solid-state lithium sulfur batteries (ASSLSBs) hold significant promise in the application of high energy density batteries, yet they suffer from poor ionic conductivity, low Li+ transference number and unsatisfactory lithium polysulfides (LiPSs) conversion. In this paper, porous-dual-shell structure and heterojunction Co3O4@NiCo2O4 is prepared and composited with polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) to address these problems. The superimposed electric field for Co3O4@NiCo2O4 composed of the heterointerfaces -build-in electric field and the surface oxygen-rich vacancies-build-in electric field facilitates the dissociation of Li salts, thus improving the ionic conductivity. It exhibits high ionic conductivity of 1.04 × 10-3 S/cm and Li+ transference number of 0.48 at 60 °C. Besides, the incorporation of Co3O4@NiCo2O4 heterojunction enables fast LiPSs conversion and improves the electrochemical kinetics. The Li//Li cell can work stably for 1100 h at 0.1 mA/cm2. The Li//S cell provides an initial capacity of 1170 mA h/g, a reversible capacity of 620.1mA h/g after 100 cycles and 308.3 mA h/g after 450 cycles at 0.2 C.

An in situ-boosted electrochemiluminescence biosensor for serotonin detection sensitized with Co3O4 nanoplates and self-feedback DNA recycling

Here, we described an in situ-boosted electrochemiluminescence (ECL) biosensor for serotonin detection sensitized with the catalysis of Co3O4 nanoplates and self-feedback DNA recycling (SFDR). Specifically, aptamer:S duplex was attached onto the surface of magnetic beads via amide bond. When serotonin presented, it competitively combined with aptamer from aptamer:S duplex. Then, the released S strands reacted with hairpin DNA (H) containing the silenced Mg2+-assisted DNAzyme site in the loop part that immobilized on CdS quantum dots (CdS QDs) modified electrode. The activating Mg2+-assisted DNAzyme cut off H and re-liberated S strands. Therefore, the Mg2+-DNAzyme-aided recycle happened to produce numerous residual single-stranded DNA segments and then reacted with Co3O4-modified P strands on the electrode surface. Such results directly introduced Co3O4 nanoplates close to CdS QDs, resulting in the reduction of H2O2 to •OH and the increase of ECL emission of CdS QDs in CdS QDs-H2O2 system. Based on such signal amplification strategy, a low detection limit of 1.5 pM was obtained for serotonin detection. This approach enabled the proposed ECL biosensor promising for the future application in the trace detection of serotonin.

Photothermal enhanced bifunctional catalyst for overall water splitting with phosphide heterojunction Fe2P-CoMoP

The development of cost-effective bifunctional electrocatalysts remains a great challenge. In this work, high-performance Fe2P-CoMoP/NF catalysts were prepared using the strategy of constructing phosphide heterostructures with localized photothermal effect. At 10 mA·cm-2, the HER overpotential of Fe2P-CoMoP/NF is 30.8 mV and the OER overpotential is 180.9 mV. Compared to Fe2P/NF and CoMoP/NF, the higher content of oxygen vacancies in the phosphorylated heterostructure Fe2P-CoMoP/NF has the potential to enhance intrinsic activity and improve the photothermal effect. With the assistance of localized photothermal effect, the HER (η100 = 72.7 mV) and OER (η100 = 252.3 mV) overpotentials of Fe2P-CoMoP/NF decreased by 35.8 % and 9.9 %, which were more significant than those of CoMoP/NF and Fe2P/NF. Meanwhile, the Fe2P-CoMoP/NF catalyst has excellent stability, maintaining 96 % at -500 mA·cm-2 and 94 % at 300 mA·cm-2 after 100 h. In addition, overall water splitting can be carried out using solar panels with a voltage of 1.42 V, which shows its potential for application in combination with sustainable energy sources.

Efficient Electrochemical-Enzymatic Conversion of PET to Formate Coupled with Nitrate Reduction Over Ru-Doped Co3O4 Catalysts

Electrochemical reforming presents a sustainable route for the conversion of nitrate (NO3 -) and polyethylene terephthalate (PET) into value-added chemicals, such as ammonia (NH3) and formic acid (HCOOH). However, its widespread application has been constrained by low selectivity due to the complexity of reduction processes and thus energy scaling limitations. In this study, the atomically dispersed Ru sites in Co3O4 synergistically interact with Co centers, facilitating the adsorption and activation of hydroxyl radicals (OH*) and ethylene glycol (EG), resulting in a remarkable HCOOH selectivity of 99% and a yield rate of 11.2 mmol h-1 cm-2 surpassing that of pristine Co3O4 (55% and 3.8 mmol h-1 cm-2). Furthermore, when applied as a bifunctional cathode catalyst, Ru-Co3O4 achieves a remarkable Faradaic efficiency (FE) of 98.5% for NH3 production (3.54 mmol h-1 cm-2) at -0.3 V versus RHE. Additionally, we developed a prototype device powered by a commercial silicon photovoltaic cell, enabling on-site solar-driven production of formate and NH3 through enzyme-catalyzed PET and NO3 - conversion. This study offers a viable approach for waste valorization and green chemical production, paving the way for sustainable energy applications.

Hierarchical Fe-based electrocatalyst for lattice oxygen mediated water oxidation with Industrial-Level activity

Rational design transition metal-based electrocatalysts for oxygen evolution reaction (OER) at large current densities is vital for industrial applications of alkaline water electrolysis. Here, we present a three-dimensional catalyst comprises of Fe2O3 nanoparticles that are highly dispersed on FeMoO4 nanorods, supported on Ni foam, featuring a hierarchical heterostructure and array morphology. The resulting Fe2O3/FeMoO4/NF electrodes exhibit remarkable OER catalytic activity, achieving overpotentials of 315 mV and 352 mV at current densities of 1000 mA cm-2 and 2000 mA cm-2, respectively, while maintaining outstanding long-term durability (>900 h) at a current density of 500 mA cm-2. In-situ Fourier-transform infrared (FTIR) spectroscopy and theoretical studies demonstrate the direct OO radical coupling for lattice-oxygen-mediated mechanism (LOM)-dominated O2 evolution, thereby breaking the scaling relationship limitation and accelerating reaction kinetics. Operando electrochemical impedance spectroscopy implies fast charge transport. The superior OER performance can be attributed to the abundant heterointerfaces between the active phases in hierarchical structure and the enhanced intrinsic activity through the LOM mechanism. This work paves an avenue for constructing advanced electrocatalysts with industrial-level activity and offering a promising approach for practical applications in alkaline water electrolysis.

Zincate Ion Enables M(II)-Vacancy NiFe Layered Double Hydroxide for Stable Seawater Electrolysis at 3 A cm-2

Seawater electrolysis offers a sustainable route for hydrogen production. Operating at high current densities can improve the energy efficiency but requires anodes that can sustain high oxygen evolution reaction (OER) activity, selectivity, and stability against negative effects of Cl-. Herein, NiFeZn layered double hydroxide (NiFeZn-LDH) demonstrates remarkable OER performance, requiring only 220 mV overpotential to achieve 10 mA cm-2, and maintaining 100% selective seawater oxidation to oxygen for 500 h at an unprecedented current density of 3 A cm-2, with minimal degradation. Through comprehensive characterizations, it is found that the dissolution of the amphoteric Zn-site and the following formation of Zn2+ vacancies are key to the excellent OER activity. The free Zn2+ in electrolyte converts to Zn(OH)4 2- and adsorbs onto the electrode, facilitating the OH- nucleophilic attack by disrupting the hydrogen bond network at the electrochemical interface. Furthermore, the steric hindrance of Zn(OH)4 2- suppresses the Cl- competing adsorption, ensuring 100% OER selectivity and long-term stability. As a result, an industrial-scale electrolyzer with NiFeZn-LDH as the anode operates stably for over 700 h in a saturated NaCl electrolyte, consuming only 4.26 Nm-3 H2. This work demonstrates the feasibility of developing energy-efficient, highly stable seawater electrolyzers that outperform conventional water electrolyzers.

Van der Waals heterostructures via spontaneous self-restacked assembling for enhanced water oxidation

The pursuit of sustainable energy solutions has identified water oxidation as a crucial reaction, with the oxygen evolution reaction (OER) serving as a decisive efficiency determinant in water technologies. This study presents a novel van der Waals (vdW) heterostructure catalyst, synthesized through a spontaneous self-restacking of nickel-iron-based phosphorus-sulfur compounds (NiPS3 and FePS3). Density Functional Theory (DFT) calculations underpinned the thermodynamic spontaneity of the restacking process, uncovering an electronic transition that significantly amplifies electrocatalytic functionality. The catalyst demonstrates a remarkable OER performance, achieving a low overpotential of 257 mV at 20 mA cm-2 and a Tafel slope of 49 mV dec-1 and demonstrates remarkable durability sustaining 500 mA cm-2 for 140 hours. In addition to its high performance, the material's rapid reconstruction facilitated by surface electron enrichment and the release of phosphate and sulfate during the OER underscores a dual enhancement in both activity and stability. The universality of the synthesis method is further demonstrated by extending the approach to other MPS3 materials (M = Mn, Co, Zn), establishing a generalized platform for developing high-performance OER catalysts. This work represents a significant advancement in the application of restacked vdW heterostructures as a foundation for advanced electrocatalytic materials.

Anodic Oxidation-Induced Interfacial Regulation of Nanoporous Co2P/CoOOH for Electrocatalytic Nitrate Reduction to Ammonia

The rechargeable Zn-nitrate battery presents a promising strategy for renewable energy conversion, ammonia production, and sewage treatment. Despite achieving excellent performance with transition metal-based electrocatalysts, the structure evolution of the electrocatalyst during Zn-nitrate battery charging/discharging and the corresponding reaction mechanism on nitrate reduction reaction (NO3RR) are still unclear. Inspired by the structural reconstruction in the charging process, nanoporous Co2P/CoOOH prepared by dealloying and anodic oxidation is reported as an electrocatalyst for NO3RR, achieving remarkable catalytic performance (ammonia yield rate: 1.93 mmol h-1 cm-2, Faradaic efficiency: 94.18%) with a high cathodic energy efficiency of 34.51%. Additionally, the assembled rechargeable Zn-nitrate battery delivers a power density of 31.99 mW cm-2 with a high charge-discharge stability. In-situ spectroscopy investigation reveals the generation of a Co2P/Co3O4 heterosturcture through a synergetic redox reaction involving the cobalt species and nitrate ions during NO3RR, which enhances the approach of potassium-ionized water and improves ammonia generation kinetics by regulating the NO2- and *NH2 generation. Density functional theoretical calculation further illustrates that Co2P/Co3O4 heterostructure optimizes the adsorption of the *NO intermediate and enables an energetically favorable rate-limiting *NOH formation step. The unique structural evolution and nitrate activation mode of cobalt-based heterostructure would provide new insights on designing efficient electrocatalysts for nitrate reduction and rechargeable Zn-nitrate battery.

Rapid synthesis of metastable materials for electrocatalysis

Metastable materials are considered promising electrocatalysts for clean energy conversions by virtue of their structural flexibility and tunable electronic properties. However, the exploration and synthesis of metastable electrocatalysts via traditional equilibrium methods face challenges because of the requirements of high energy and precise structural control. In this regard, the rapid synthesis method (RSM), with high energy efficiency and ultra-fast heating/cooling rates, enables the production of metastable materials under non-equilibrium conditions. However, the relationship between RSM and the properties of metastable electrocatalysts remains largely unexplored. In this review, we systematically examine the unique benefits of various RSM techniques and the mechanisms governing the formation of metastable materials. Based on these insights, we establish a framework, linking RSM with the electrocatalytic performance of metastable materials. Finally, we outline the future directions of this emerging field and highlight the importance of high-throughput approaches for the autonomous screening and synthesis of optimal electrocatalysts. This review aims to provide an in-depth understanding of metastable electrocatalysts, opening up new avenues for both fundamental research and practical applications in electrocatalysis.

Boosting Urea Electrosynthesis via Asymmetric Oxygen Vacancies in Zn-Doped Fe2O3 Catalysts

Urea electrosynthesis from CO2 and nitrate (NO3 -) provides an attractive pathway for storing renewable electricity and substituting traditional energy-intensive urea synthesis technology. However, the kinetics mismatching between CO2 reduction and NO3 - reduction, as well as the difficulty of C─N coupling, are major challenges in urea electrosynthesis. Herein, we first calculated the free energy of *CO, *OCNO, and *NOH formation over defect-rich Fe2O3 catalysts with different metal dopants, which showed that Zn dopant was a promising candidate. Based on the theoretical study, we developed Zn-doped defect-rich Fe2O3 catalysts (Zn-Fe2O3/OV) containing asymmetric Zn-OV-Fe sites. It exhibited an outstanding urea faradaic efficiency of 62.4% and the remarkable recycling stability. The production rate of urea was as high as 7.48 mg h-1 mgcat -1, which is higher than most of the reported works to date. Detailed control experiments and in situ spectroscopy analyses identified *OCNO as a crucial intermediate for C─N coupling. The Zn-Fe2O3/OV catalyst with asymmetric Zn-OV-Fe sites showed enhanced *CO coverage and promoted *OCNO formation, leading to high efficiency toward urea production.

Foreign cation-promoted active species formation enables efficient electrochemical glycerol valorization

The foreign cation substitution approach to Ni-Co spinel oxide promotes the active NiOOH species formation, resulting in remarkable electrochemical glycerol oxidation activity and selectivity for formate production. The generated NiOOH improves both the indirect GOR and the coadsorption capacity of OH* and glycerol, which is crucial to the potential-dependent GOR mechanism.

Surface-enhanced Raman scattering probes based on sea urchin-like Bi2S3@Co3O4 composite for the detection of dopamine during neural stem cell differentiation

Dopamine (DA) is a significant neurotransmitter involved in various functions of the central nervous system, containing the regulation of motor functions, arousal, motivation and reward processing. Therefore, precise measurement of DA concentrations is vital for studying different dopaminergic neural pathways and for the diagnosis of neurological disorders. Herein, we developed a new semiconductor surface-enhanced Raman spectroscopic (SERS) platform designed for the real-time monitoring DA release from live cells with high selectivity and sensitivity. The sea urchin-like Bi2S3@Co3O4 composite substrate exhibited not only a wide linear range from 1.00 to 1.00 × 103 nmol/L but also a limit of detection (LOD) as low as 0.92 nmol/L for Methylene Blue (MB) molecules. In addition, we monitored DA release during the differentiation of neural stem cells (NSCs) into dopaminergic neurons by virtue of our constructed SERS platform in a nondestructive and in situ manner. Consequently, the developed SERS platform facilitates the direct detection of exocytotic DA from neuronal cells, enabling real-time assessment of cell viability in models of neurodegenerative disease-related cellular damage.

Nitrogen-doped carbon nanotube encapsulated CoCu bimetallic alloy particles to promote efficient oxygen evolution reaction via electronic structure regulation

The rational design of efficient and cost-effective transition metal alloy electrocatalysts represents a huge challenge for the oxygen evolution reaction (OER). Herein, the bimetallic CoCu-MOF is employed as a template to significantly enhance the catalytic activity through in situ pyrolysis into melamine-assisted nitrogen-doped carbon nanotube (NCNT) encapsulated metal alloy electrocatalyst (Co1Cu1@NCNT/CC). The Co1Cu1@NCNT/CC demonstrates superior OER activity in 1 M KOH. The overpotential is 263 mV at 10 mA cm-2. Meanwhile, the catalyst exhibits superior long-term stability. The experimental results and density functional theory (DFT) calculations reveal the bimetallic synergies regulate the electronic structure and strong electronic metal-support interaction (EMSI) of the catalysts, increase the electron transport efficiency and optimize the adsorption capacity of oxygen-containing intermediates, leading to a significant improvement in both the OER activity and stability.

Fe doping intensifies the built-in electric field for tailoring the reconstruction of sulfides towards efficient oxygen evolution

The traditional view of sulfides as stable active centers has hindered the development of a clear structure-activity relationship and the rational design of high-performance oxygen evolution reaction (OER) catalysts. In this study, we focus on regulating sulfide reconstruction and have synthesized a Fe-Ni3S4/Cr2O3 pre-catalyst. Under the combined influence of the built-in electric field (BIEF) at the heterogeneous interface and Fe doping, both the sulfide reconstruction process and the electronic structure of the reconstructed product, namely Fe-NiOOH, were effectively tuned. The enhanced BIEF induced by Fe doping generated electron-rich regions on the sulfide surface, stabilizing the reconstruction process. Fe doping into the sulfide induced the incorporation of Fe into NiOOH, modulating the electronic states near the Fermi level of the metal-oxygen bond and subsequently activating the lattice oxygen mediated mechanism (LOM) of Fe-NiOOH, which serves as the true active center. Additionally, the BIEF optimized OH- diffusion dynamics and the energy consumption of hydroxyl deprotonation, reducing the energy barrier of the rate-limiting step of the LOM process, further enhancing OER activity. Remarkably, Fe-Ni3S4/Cr2O3 demonstrated excellent OER activity and commercial viability. This work offers a new perspective on the regulation of reconstruction products of pre-catalyst, providing fresh insights for the design of efficient OER catalysts.

Iodine-Induced Redirection of Active Sources in Cu-Based Catalysts during Efficient and Stable Water Oxidation

Enhancing the mechanistic regulation of the oxygen evolution reaction (OER) is crucial for developing efficient and stable electrocatalysts. However, the dynamic variation of surface structure during the electrocatalytic process limits the accurate identification of the active source and underlying reaction mechanism. Herein, we report an iodine-doping strategy to direct the reconstruction of active species in CuS catalysts toward an unconventional oxygen vacancy oxidation mechanism, thereby overcoming the activity and stability limitations. Mechanistic analysis indicates that the electronic manipulation, weak coordination of Cu-S bonds, and lattice distortion induced by iodine-doping facilitate the thermodynamically favorable Cu2+ to Cu3+ oxidation during OER. The decisively formed oxygen vacancies are emphasized as a genuine active source to promote hydroxyl adsorption, with hypervalent Cu species acting as auxiliary sites to accelerate deprotonation by strengthening Cu-O covalent. Consequently, the optimal iodine-doped CuS exhibits a reduced overpotential of 189 mV at 10 mA cm-2 and superb stability prolonging to 1250 h. When used as a bifunctional electrode in a membrane electrode assembly electrolyzer, it also exhibits a low voltage of 1.65 V at 1 A cm-2, with electrolysis durability of 480 h and a low hydrogen cost of US$1.70/kg H2, outperforming the 2026 targets set by the U.S. Department of Energy.

Solid-Liquid Interfacial Hydrogen Bond-Mediated Mass Transfer Toward Industrial Water Electrolysis

The rapid migration of reactive ions across the electrolyte-catalytic sites interface is crucial in various catalytic processes. Herein, we introduce hydrogen bonds to bridge the intrinsic gap at the catalyst-electrolyte interface, mediating the diffusion of hydroxide ions. We implemented the aforementioned concept by a library of oxyanions functionalized NiCo OOH, wherein the oxygen atom within the oxyanions established hydrogen bonds with H2O molecules in the electrolyte. Operando spectroscopy indicated that both water electrolysis activity and hydroxide concentration exhibited a volcano-shaped dependence on the electrostatic potential of functionalized group, which formulated the electrostatic potential as descriptors to guide the design of interfacial hydrogen bond-mediated catalysis. The sulfate-modified NiCo OOH achieved an ultralow energy consumption of 4.23 kWh m-3 H2 in the industrial electrolyzers, predicting that the electricity consumption can be reduced by 16 000 TWh.

Fluorine Engineering Induces Phase Transformation in NiCo2O4 for Enhanced Active Motifs Formation in Oxygen Evolution Reaction

Dynamic reconstruction of catalysts is key to active site formation in alkaline oxygen evolution reaction (OER), but precise control over this process remains challenging. Herein, F-doped NiCo2O4 (NiCo2O4-Fn), consisting of a NiCo2O4 core and a (NH4)NixCo1-xF3 shell is reported, which promotes the formation of a dual-metal NiCoOOH active phase. In situ Raman and X-ray absorption fine structure analyses reveal that the NiCoOOH, rich in oxygen vacancies (Ov), forms at 1.2 V versus the reversible hydrogen electrode (RHE) for NiCo2O4-F1, in contrast to the NiOOH phase formation at 1.4 V versus RHE for undoped NiCo2O4. This is facilitated by the transformation of (NH4)NixCo1-xF3 into amorphous NixCo1-x(OH)2 in the KOH electrolyte without bias. Electrochemical tests show that NiCo2O4-F1 exhibits a 14-fold increase in intrinsic activity compared to NiCo2O4. Theoretical calculations suggest that Ov-induced unsaturated Co and Ni sites enhance electroactivity by promoting *OH intermediates adsorption and conversion, lowering the OER energy barrier. The oriented control of NiCoOOH active motifs in NiCo2O4 spinel, achieved through fluorine engineering, paves a new avenue for designing efficient OER electrocatalysts.

Anchoring platinum clusters in CoP@CoNi layered double hydroxide to prepare high-performance and stable electrodes for efficient water splitting at high current density

Hydrogen production via electrocatalytic water splitting has garnered significant attention, due to the growing demand for clean and renewable energy. However, achieving low overpotential and long-term stability of water splitting catalysts at high current densities remains a major challenge. Herein, a CoP@CoNi layered double hydroxide (LDH) electrode was synthesized via a two-step electrodeposition process, demonstrating oxygen evolution reaction, with an overpotential (ƞ400) of 373 mV and a Tafel slope of 64.2 mV/dec. Subsequently, a superhydrophilic CoP@CoNi LDH-Pt electrode was prepared using an in situ oxidation method, with Pt clusters anchored within the CoP@CoNi LDH for the hydrogen evolution reaction, with an overpotential (ƞ400) of 119 mV and a Tafel slope of 33.6 mV/dec. The CoP@CoNi LDH-Pt||CoP@CoNi LDH system achieved a cell voltage of 1.96 V at 1000 mA/cm2, maintaining stable performance after water electrolysis for 160 h. These remarkable outcomes stem from the fast charge transfer, improved mass transfer, and superior stability of the catalysts. Heterostructure electrodes were constructed to optimize the electrocatalytic kinetics through strong interfacial electronic interactions, while superhydrophilic electrodes were fabricated to improve the mass transfer process at a high current density. Anchoring high-activity components in catalysts prevents their detachment during water electrolysis, enhancing the structural stability of the electrodes. This study provides a new approach for large-scale preparation of efficient water electrolysis catalysts and offers significant potential for industrial hydrogen production applications.

Local Electronic Regulation by Oxygen Coordination with Single- Atomic Iridium on Ultrathin Cobalt Hydroxide Nanosheets for Electrocatalytic Oxygen Evolution

Rationally optimizing the atomic and electronic structure of electrocatalysts is an effective strategy to improve the activity of the electrocatalytic oxygen evolution reaction (OER), yet it remains challenging. In this work, atomic heterointerface engineering is developed to accelerate OER by decorating iridium atoms on low-crystalline cobalt hydroxide nanosheets (Ir-Co(OH)x) via oxygen-coordinated bonds to modulate the local electronic structure. Leveraging detailed spectroscopic characterizations, the Ir species were proved to promote charge transfer through Ir-O-Co coordination between the Ir atom and the Co(OH)x support. As a result, the optimized Ir-Co(OH)x exhibits excellent electrocatalytic OER activity with a low overpotential of 251 mV to drive 10 mA cm-2, which is 63 mV lower than that of pristine Co(OH)x. The experimental results and density functional theory calculations reveal that the isolated Ir atoms can regulate the local coordination environment and electronic configuration of Co(OH)x, thus accelerating the catalytic OER kinetics. This work provides an atomistic strategy for the electronic modulation of metal active sites in the design of high-performance electrocatalysts.

Electrochemically superior ammonia production from electroplating wastewater over oxygen-incorporated antiperovskite

The electrochemical reduction of nitrates from real electroplating wastewater to ammonia offers an appealing solution for environmental sustainability and waste recycling. However, the slow charge transfer between the catalyst and adsorbent limits their catalytic performance. Herein, a typical oxygen-incorporated Cu0.5NFe3.5 antiperovskite was synthesized successfully using the magneto-thermal stimulation strategy, achieving an impressive ammonia yield rate of 1.34mmol h-1 cm-2 and a high Faradaic efficiency of 95.5 % at -0.6 V vs. RHE. Furthermore, we developed a membraneless flow electrolyzer paired with an ammonia recovery device that synchronizes nitrate reduction and ammonia recovery for treating real electroplating wastewater. This work presents a viable approach for developing high-performance oxygen-incorporated antiperovskites suitable for treating real electroplating wastewater.

Zr doping Co3O4 nanowires mediated adsorption of chloridion for efficient natural seawater electrolysis

Natural seawater electrolysis is emerging as a desirable approach for hydrogen production, but it suffers from long-term instability due to severe chloride corrosion. In this study, Zr doped Co3O4 is proposed for natural seawater oxidation, which requires an overpotential of only 570 mV to drive a current density of 100 mA cm-2, and a sustained natural seawater electrolysis at 10 mA cm-2 for 500h exhibits only 0.78 % decay. For practicability, membrane electrode with a self-developed anion exchange membrane is assembled for overall natural seawater electrolysis, and the produced hydrogen is converted to ammonia for storage by coupling nitrate reduction. Density functional theory (DFT) calculations further reveal Zr replacing an octahedral Co atom introduces four energy levels within the gap and the lower conduction band energy is formed by substituting a tetrahedral Co atom. The highest energy barrier of the second dehydrogenation step (*OH to *O) reaches 1.82 eV and it is slightly reduced to 1.79 eV after Co3O4 is transformed to CoOOH. Zr-adsorbed chloridion sharply increases its absorption energy on Co sites to a positive value of 0.27 eV, which effectively protects Co active sites from chloride attack.

In Situ Grown RuNi Alloy on ZrNiNx as a Bifunctional Electrocatalyst Boosts Industrial Water Splitting

Alkaline water electrolysis represents a pivotal technology for green hydrogen production yet faces critical challenges including limited current density and high energy input. Herein, a heterostructured bimetallic nitrides supported RuNi alloy (RuNi/ZrNiNx) is developed through in situ epitaxial growth under ammonolysis, achieving exceptional bifunctional activity and durability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH electrolyte. The RuNi/ZrNiNx exhibits a HER current density of -2 A cm-2 at an overpotential of 392.8 mV, maintaining initial overpotential after 1000 h continuous electrolysis at -500 mA cm-2. For OER, it delivers a current density of 2 A cm-2 at 1.822 V versus RHE, and sustains stable operation for 705 h at 500 mA cm-2. Experimental and theoretical studies unveil that the charge redistribution-induced high-valence Zr centers effectively polarize H─O bonds and promote water dissociation, and the electron-deficient interface Ru sites optimize hydrogen desorption kinetics. Dynamic OH spillovers from Zr sites to the adjacent tri-coordinated Ni hollow sites in NiNx promote rapid *OH intermediate desorption and active site regeneration. Notably, the tri-coordinated Ni hollow sites in NiNx proximal to Zr atoms exhibit tailored adsorption strength for oxo-intermediates, enabling a more energetically favorable pathway for O2 production.

Phase Engineering Modulates the Electronic Structure of the IrO2/MoS2 Heterojunction for Efficient and Stable Water Splitting

The engineering of dual-functional catalytic systems capable of driving complete water dissociation in acidic environments represents a critical requirement for advancing proton exchange membrane electrolyzer technology, yet significant challenges remain. In this work, we investigate an IrO2/MoS2/CNT heterostructure catalyst demonstrating enhanced bifunctional performance for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under acidic conditions. Strategic incorporation of IrO2 into the MoS2/CNT heterojunction induces a partial phase transformation from 2H to the metastable 1T configuration in MoS2, thereby modulating the electronic structure of IrO2 and improving the catalytic performance for overall water splitting. The optimized IrO2/MoS2/CNT catalyst exhibited exceptional overpotentials of 9 mV (HER) and 182 mV (OER) at a current density of 10 mA cm-2 in acidic media. Full-cell evaluations further confirmed its practical potential, showing a 1.47 V operation voltage that outperforms standard Pt/C||IrO2 counterparts by 120 mV. The experimental results revealed that the n-n heterojunction between IrO2/CNT and MoS2/CNT generates a built-in electric field, enhancing charge redistribution and electron transport. Moreover, density functional theory simulations further identify iridium centers as dominant catalytic loci, with a metastable 1T-MoS2 phase mediating charge equilibration at atomic interfaces. This modification facilitates *OH adsorption and *OOH deprotonation and lowers the kinetic barrier during the water-splitting process.

Proton Exchange Membrane Water Splitting: Advances in Electrode Structure and Mass-Charge Transport Optimization

Proton exchange membrane water electrolysis (PEMWE) represents a promising technology for renewable hydrogen production. However, the large-scale commercialization of PEMWE faces challenges due to the need for acid oxygen evolution reaction (OER) catalysts with long-term stability and corrosion-resistant membrane electrode assemblies (MEA). This review thoroughly examines the deactivation mechanisms of acidic OER and crucial factors affecting assembly instability in complex reaction environments, including catalyst degradation, dynamic behavior at the MEA triple-phase boundary, and equipment failures. Targeted solutions are proposed, including catalyst improvements, optimized MEA designs, and operational strategies. Finally, the review highlights perspectives on strict activity/stability evaluation standards, in situ/operando characteristics, and practical electrolyzer optimization. These insights emphasize the interrelationship between catalysts, MEAs, activity, and stability, offering new guidance for accelerating the commercialization of PEMWE catalysts and systems.

Unveiling Surface Species Formed on Ni-Fe Spinel Oxides During the Oxygen Evolution Reaction at the Atomic Scale

Optimizing electrocatalyst performance requires an atomic-scale understanding of surface state changes and how those changes affect activity and stability during the reaction. This is particularly important for the oxygen evolution reaction (OER) since the electrocatalytically active surfaces undergo substantial reconstruction and transformation. Herein, a multimodal method is employed that combines X-ray photoemission spectroscopy, transmission electron microscopy, atom probe tomography, operando surface-enhanced Raman spectroscopy with electrochemical measurements to examine the surface species formed on NiFe2O4, P-doped NiFe2O4 and Ni1.5Fe1.5O4 upon OER cycling. The activated NiFe2O4 and P-doped NiFe2O4 exhibit a significantly lower Tafel slope (≈40 mV dec-1) than Ni1.5Fe1.5O4 (≈90 mV dec-1), although oxyhydroxides are grown on all three Ni-Fe spinels during OER. This is likely attributed to the formation of a ≈1 nm highly defective layer with a higher oxygen concentration on the activated NiFe2O4 and P-doped NiFe2O4 nanoparticle surfaces (than that in bulk), which improves the charge transfer kinetics toward OER. Such surface species are not formed on Ni1.5Fe1.5O4. Overall, this study provides a mechanistic understanding of the role of Fe, P, and Ni in forming active oxygen species in the Ni-based spinels toward OER.

Scalable and efficient electrochemical bromination of arenes with Faradaic efficiencies surpassing 90

Developing cost-effective and environmentally friendly approaches to synthesize brominated chemicals, which are important intermediates for the synthesis of various useful molecules such as pharmaceuticals, surfactants, pesticides, and biologically active heterocyclic compounds, is of great significance. Herein, we present a highly efficient electrochemical bromine evolution reaction over vacancy rich Co3O4 using cheap NaBr as the bromine source for the synthesis of valuable brominated fine chemicals and pharmaceuticals under ambient conditions. The introduction of oxygen vacancy onto Co3O4 can greatly enhance the activity and selectivity of bromine evolution reaction by optimizing Br* intermediate adsorption and desorption, enabling bromination of a series of bioactive molecules and pharmaceuticals at high yields.

Efficient co-production of ammonia and formic acid from nitrate and polyester via paired electrolysis

Paired electrolysis, which integrates a productive cathodic reaction, such as the nitrate reduction reaction (NO3-RR) with selective oxidation at the anode, offers an intriguing way to maximize both atomic and energy efficiency. However, in a conventional design, the NO3-RR is often coupled with the anodic oxygen evolution reaction, leading to substantial energy consumption while yielding low-value oxygen. Here, we report a hybrid electrolysis system that combines cathodic reduction of nitrate to ammonia and anodic oxidation of polyethylene-terephthalate-derived ethylene glycol (EG) to formic acid (FA), utilizing oxygen-vacancy-rich (OV) Co3O4 and Cu doped Ni(OH)2 as the cathode and anode, respectively. Remarkably, this paired electrolysis system demonstrates a faradaic efficiency (FE) of 92% for cathodic ammonia production and a FE of 99% for anodic FA production, while reducing the cell voltage by 0.54 V compared to the conventional NO3-RR system at the same current density of 100 mA cm-2. Experimental investigations combined with theoretical calculations reveal that the OV introduction effectively addresses the insufficient NO3- adsorption and hydrogenation on bare Co3O4. Additionally, Cu incorporation increases the Ni-O covalency, resulting in an improved EG adsorption ability. This work presents a promising way for waste management via paired electrolysis.

Lewis Acid Sites in Hollow Cobalt Phytate Micropolyhedra Promote the Electrocatalytic Water Oxidation

The acid-base microenvironment of the metal center is crucial for constructing advanced oxygen evolution reaction (OER) electrocatalysts. However, the correlation between acidic site and OER performance remains unclear for cobalt-based catalysts. Herein, Lewis acid sites in hollow cobalt phytate micropolyhedra (M-CoPA, M = Cu, Sr) were synthesized by a cation-exchange strategy, and their OER performances were studied systematically. Experimentally, Lewis acid Cu2+ sites with stronger Lewis acidity exhibited superior intrinsic activity and long-term stability in alkaline electrolytes. The spectroscopic and electrochemical studies show Lewis acid sites in hollow cobalt phytate micropolyhedra can modulate the electronic distribution of the adjacent cobalt center and further optimize the adsorption strength of oxygenated species. This study figures out the effect of Lewis acid sites on the OER kinetics and provides an effective way to develop high-efficiency electrocatalysts for energy conversion systems.

Insight into the structural reconstruction of alkaline water oxidation electrocatalysts

The oxygen-evolution reaction (OER) is an indispensable component of various energy storage and conversion electrocatalytic systems. However, the slow reaction kinetics have forced the development of advanced, efficient, and inexpensive OER electrocatalysts to break through the bottleneck of its application. Recently, the structural reconstruction of precatalysts has provided a promising avenue to boost the catalytic activity of electrocatalysts. Structural reconstruction implies atomic rearrangement and composition change of the pristine catalytic materials, which is a very complex process. Therefore, it is very crucial to have a deep understanding of the reconstruction chemical process and then modulate the reconstruction by deliberate design of electrochemical conditions and precatalysts. However, a systematic review of the structural reconstruction process, research methods, influencing factors and structure-performance relationship remains elusive, significantly impeding the further developments of efficient electrocatalysts based on structural reconstruction chemistry. This critical review is dedicated to providing a deep insight into the structural reconstruction during alkaline water oxidation, comprehensively summarizing the basic research methods to understand the structural evolution process and various factors affecting the structural reconstruction process, and providing a reference and basis for regulating the dynamic reconstruction. Moreover, the impact of reconstruction on the structure and performance is also covered. Finally, challenges and perspectives for the future study on structural reconstruction are discussed. This review will offer future guidelines for the rational development of state-of-the-art OER electrocatalysts.

Self-Etching Synthesis of Superhydrophilic Iron-Rich Defect Heterostructure-Integrated Catalyst with Fast Oxygen Evolution Kinetics for Large-Current Water Splitting

Developing catalysts with rich metal defects, strong hydrophilicity, and extensive grain boundaries is crucial for enhancing the kinetics of electrocatalytic water oxidation and facilitating large-current water splitting. In this study, we utilized pH-controlled etching and gas-phase phosphating to synthesize a flower-like Ni2P-FeP4-Cu3P modified nickel foam heterostructure catalyst. This catalyst features pronounced hydrophilicity and a high concentration of Fe defects. It exhibits low overpotentials of 156 mV and 210 mV at current densities of 10 and 100 mA cm-2 respectively, and maintains stability for up to 200 h at 100 mA cm-2 with only 7.3 % degradation, showcasing outstanding electrocatalytic water oxidation performance. Furthermore, when integrated into a Ni2P-FeP4-Cu3P/NF||Pt-C/NF electrolyzer, it achieves excellent overall water splitting performance, reaching current densities of 10 and 400 mA cm-2 at just 1.47 V and 1.73 V, respectively, and operates stably for 60 h at 500 mA cm-2 with minimal degradation. Analysis indicates that high-valence oxyhydroxides/phosphides of Ni, Fe, and Cu act as the primary active species. The presence of abundant Fe defects enhances electron transfer, strong hydrophilicity improves electrolyte contact, and numerous grain boundaries synergistically modulate the activation energy between active sites and oxygen-containing intermediates, significantly improving the kinetics of water oxidation.

A Review of Surface Reconstruction and Transformation of 3d Transition-Metal (oxy)Hydroxides and Spinel-Type Oxides during the Oxygen Evolution Reaction

Developing efficient and sustainable electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy conversion and storage technologies. 3d transition-metal (oxy)hydroxides and spinel-type oxides have emerged as promising candidates due to their structural flexibility, oxygen redox activity, and abundance in earth's crust. However, their OER performance can be changed dynamically during the reaction due to surface reconstruction and transformation. Essentially, multiple elementary processes occur simultaneously, whereby the electrocatalyst surfaces undergo substantial changes during OER. A better understanding of these elementary processes and how they affect the electrocatalytic performance is essential for the OER electrocatalyst design. This review aims to critically assess these processes, including oxidation, surface amorphization, transformation, cation dissolution, redeposition, and facet and electrolyte effects on the OER performance. The review begins with an overview of the electrocatalysts' structure, redox couples, and common issues associated with electrochemical measurements of 3d transition-metal (oxy)hydroxides and spinels, followed by recent advancements in understanding the elementary processes involved in OER. The challenges and new perspectives are presented at last, potentially shedding light on advancing the rational design of next-generation OER electrocatalysts for sustainable energy conversion and storage applications.

Coupling Built-in Electric Field and Lewis Acid Triggers the Lattice Oxygen-Mediated Mechanism for Efficient Water Oxidation

The oxygen evolution reaction catalyst triggering lattice oxygen-mediated mechanism (LOM) can break the activity limitation imposed by the adsorbate evolution mechanism scaling relationship. However, triggering LOM is challenging due to the thermodynamic disadvantages associated with lattice oxygen redox reactions. Here, a Lewis acid-modified layered double hydroxides (LDH) heterojunction catalyst (LDH/Cr2O3) is designed. The asymmetric charge distribution at the heterojunction interface, induced by the built-in electric field, shifts the electron transfer center from the lower Hubbard band to non-bonding oxygen, thereby activating LOM. The enrichment of OH- and the enhanced covalency of the metal-oxygen bond by Lewis acid optimize the pH-dependent and high-energy consumption during the hydroxyl (OH*) deprotonation process of LOM. Furthermore, the activation of lattice oxygen and accelerated OH* deprotonation facilitate the surface reconstruction of LDH. Consequently, the LDH/Cr2O3 exhibits excellent catalytic activity, with an overpotential of only 237 mV (at 10 mA cm-2) in 1.0 m KOH electrolyte. The catalyst maintains excellent activity in simulated seawater and 0.1 m KOH electrolyte. Furthermore, it demonstrates outstanding practical functionality, as the assembled commercial-scale alkaline electrolyzer operates stably for 50 h. This work may provide new approaches and theoretical insights for triggering and optimizing LOM.

A photovoltaic-electrolysis system with high solar-to-hydrogen efficiency under practical current densities

The photovoltaic-alkaline water (PV-AW) electrolysis system offers an appealing approach for large-scale green hydrogen generation. However, current PV-AW systems suffer from low solar-to-hydrogen (STH) conversion efficiencies (e.g., <20%) at practical current densities (e.g., >100 mA cm-2), rendering the produced H2 not economical. Here, we designed and developed a highly efficient PV-AW system that mainly consists of a customized, state-of-the-art AW electrolyzer and concentrator photovoltaic (CPV) receiver. The highly efficient anodic oxygen evolving catalyst, consisting of an iron oxide/nickel (oxy)hydroxide (Fe2O3-NiOxHy) composite, enables the customized AW electrolyzer with unprecedented catalytic performance (e.g., 1 A cm-2 at 1.8 V and 0.37 kgH2/m-2 hour-1 at 48 kWh/kgH2). Benefiting from the superior water electrolysis performance, the integrated CPV-AW electrolyzer system reaches a very high STH efficiency of up to 29.1% (refer to 30.3% if the lead resistance losses are excluded) at large current densities, surpassing all previously reported PV-electrolysis systems.

Ferrocene-MOFs: Optimizing OER Kinetics for Water Splitting

Optimizing the adsorption and desorption kinetics of oxygen evolution reaction (OER) is crucial for efficient overall water splitting. Herein, we report a series of porous ferrocene-based metal-organic framework (MFc-MOF, M = Co, Ni, Fe, Mn) nanoflowers featuring a close π-π stacking lattice structure as model catalysts, and explore the structure-activity relationship. Operando electrochemical impedance spectroscopy implies that the synthesized CoFc-MOF@NF facilitates intermediate adsorption and desorption. It exhibits an ultralow overpotential of 189 mV at 10 mA cm-2 and maintains stability for 250 h. In an overall water splitting device, when CoFc-MOF@NF serves as the anode, it yields a significantly lower cell voltage than commercial RuO2 and shows excellent stability at 100 mA cm-2 for 100 h. In situ Raman spectroscopy reveals that the CoFc-MOF@NF surface transforms into CoFeOOH, the OER-active species, while preserving the MOF framework. The inner MOF's ferrocene units act as efficient electron-transfer mediators. These findings highlight CoFc-MOF@NF's potential as a leading catalyst for sustainable water splitting hydrogen production, combining high catalytic activity, rapid kinetics, and robust stability. This work presents a new approach to balance activity and stability in MOF-based OER catalysts.

Strong Heteroatomic Bond-Induced Confined Restructuring on Ir-Mn Intermetallics Enable Robust PEM Water Electrolyzers

Low-iridium acid-stabilized electrocatalysts for efficient oxygen evolution reaction (OER) are crucial for the market deployment of proton exchange membrane (PEM) water electrolysis. Manipulating the in situ reconstruction of Ir-based catalysts with favorable kinetics is highly desirable but remains elusive. Herein, we propose an atomic ordering strategy to modulate the dynamic surface restructuring of catalysts to break the activity/stability trade-off. Under working conditions, the strong heteroatom-bonded structure triggers rational surface-confined reconstruction to form self-stabilizing amorphous (oxy)hydroxides on the model Ir-Mn intermetallic (IMC). Combined in situ/ex situ characterizations and theoretical analysis demonstrate that the induced strong covalent Ir-O-Mn units in the catalytic layer weaken the formation barrier of OOH* and promote the preferential dynamic replenishment/conversion pathway of H2O molecules to suppress the uncontrollable participation of lattice oxygen (about 2.6 times lower than that of pure Ir). Thus, a PEM cell with Ir-Mn IMC as anode "pre-electrocatalyst" (0.24 mgIr cm-2) delivers an impressive performance (3.0 A cm-2@1.851 V@80 °C) and runs stably at 2.0 A cm-2 for more than 2,000 h with the cost of USD 0.98 per kg H2, further validating its promising application. This work highlights surface-confined evolution triggered by strong heteroatom bonds, providing insights into the design of catalysts involving surface reconstruction.

Electrocatalysis: From Planar Surfaces to Nanostructured Interfaces

The reactions critical for the energy transition center on the chemistry of hydrogen, oxygen, carbon, and the heterogeneous catalyst surfaces that make up electrochemical energy conversion systems. Together, the surface-adsorbate interactions constitute the electrochemical interphase and define reaction kinetics of many clean energy technologies. Practical devices introduce high levels of complexity where surface roughness, structure, composition, and morphology combine with electrolyte, pH, diffusion, and system level limitations to challenge our ability to deconvolute underlying phenomena. To make significant strides in materials design, a structured approach based on well-defined surfaces is necessary to selectively control distinct parameters, while complexity is added sequentially through careful application of nanostructured surfaces. In this review, we cover advances made through this approach for key elements in the field, beginning with the simplest hydrogen oxidation and evolution reactions and concluding with more complex organic molecules. In each case, we offer a unique perspective on the contribution of well-defined systems to our understanding of electrochemical energy conversion technologies and how wider deployment can aid intelligent materials design.

Low-Level Fe Doping in CoMoO4 Enhances Surface Reconstruction and Electronic Modulation Creating an Outstanding OER Electrocatalyst for Water Splitting

Efficient and stable nonprecious metal-based oxygen evolution reaction (OER) electrocatalysts are pivotal for water electrolysis technology. Herein, we are reporting an effective strategy for fabricating efficient Co-based OER electrocatalysts by low-level Fe doping in CoMoO4 to boost surface reconstruction and electronic modulation, which resulted in excellent OER electroactivity consequently. Our findings reveal that a mere 5.30% (wt %) of Fe doping can raise the O 2p band center energy nearer to the Fermi level, reduce the energy barrier for oxygen vacancy (VO) formation, and significantly enhance OER electrocatalytic activity. Additionally, the fast dissolution of Mo in the initial reaction facilitated surface reconstruction to form active oxyhydroxide species and stabilized Fe and Co from leaching. As a result, the optimized catalyst Fe-CoMoO4-0.2 exhibited a low overpotential of 276 mV at 10 mA cm-2 in 1 M KOH and can operate stably at a current density of 20 mA cm-2 for at least 24 h under water splitting conditions. This work provides an excellent example of regulating the surface structure and electronic properties of the OER catalysts.

Aeration-Free Photo-Fenton-Like Reaction Mediated by Heterojunction Photocatalyst toward Efficient Degradation of Organic Pollutants

The regulation of peroxymonosulfate (PMS) activation by photo-assisted heterogeneous catalysis is under in-depth investigation with potential as a replaceable advanced oxidation process in water purification, yet it remains a significant challenge. Herein, we demonstrate a strategy to construct polyethylene glycol (PEG) well-coupled dual-defect VO-M-Co3O4@CNx S-scheme heterojunction to degrade organic pollutants without aeration, which dramatically provides abundant active sites, excellent photo-thermal property, and distinct charge transport pathway for PMS activation. The degradation rate of VO-M-Co3O4@CNx in anaerobic conditions shows a higher efficient rate (4.58 min-1 g-2) than in aerobic conditions (1.67 min-1 g-2). Experimental evidence reveals that VO-M-Co3O4@CNx promotes more rapid redox conversion of photoexcited electrons induced by defects with PMS under anaerobic conditions compared to aerobic conditions. Additionally, in situ experiments and DFT provide mechanistic insights into the regulation pathway of PMS activation via synergistic defect-induced electron, revealing the competitive effect between O2 and PMS over VO-M-Co3O4@CNx during the reaction process. The continuous flow reactor and flow cytometry results demonstrated that the VO-M-Co3O4@CNx/PMS/Vis system has remarkably enhanced stability and purification capability for removing organic pollutants. This work provides valuable insights into regulating the heterologous catalysis oxidation process without aeration through the photoexcitation synergistic PMS activation.

Cyanide Functionalization and Oxygen Vacancy Creation in Ni-Fe Nano Petals Sprinkled with MIL-88A Derived Metal Oxide Nano Droplets for Bifunctional Alkaline Seawater Electrolysis

This work investigates novel improvements in FeNi-layered double hydroxide (LDH)/MIL-88A heterocomposite for sustainable seawater electrolysis through a single-step dual functionalization process. The Fe/Ni precursor weight ratio is optimized, resulting in the formation of smaller LDH petals and nano-sized MIL-88A metal-organic framework, which transforms into clusters of Fe2O3 nanospheres within a nitrogen-functionalized carbon matrix over NiFe2O4 nano petals upon calcination. Furthermore, oxygen vacancies, and nitrogen functionalization are attained in a single step by employing thermal ammonia reduction, significantly improving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities. Particularly the oxygen vacancy and nitrogen functionalization are found to accelerate the O─O coupling step in OER by lowering the activation barrier. Likewise, the dual functionalization promotes destabilizing the hydride intermediates in HER potentially facilitating faster proton-coupled electron transfer. Hence, the optimized electrode achieves current densities of 200 mA cm-2 at overpotentials of 350 and 240 mV for OER and HER respectively. The chronopotentiometry stability tests confirms the electrode's durability over 200 h at 20 mA cm-2 in alkaline seawater electrolyte. The optimized electrode, composed of cost-effective and environmentally friendly materials, demonstrates robustness in alkaline seawater electrolytes, positioning it as a strong candidate for practical and sustainable water electrolysis applications.

High-Valence Metals Accelerate the Reaction Kinetics for Boosting Water Oxidation

The transition metal with high valence state in oxyhydroxides can accelerate the reaction kinetics, enabling highly intrinsic OER activity. However, the formation of high-valence transition-metal ions is thermodynamically unfavorable in most cases. Here, a novel strategy is proposed to realize the purpose and reveal the mechanism by constructing amorphous phase and incorporating of elements with the characteristic of Lewis acid or variable charge state. A model catalyst, CeO2-NiFeOxHy, is presented to achieve the modulation of valence state of active site (Ni2+→Ni3+→Ni4+) for improved OER, leading to dominant active sites with high valence state. The CeO2-NiFeOxHy electrode exhibits superior OER performance with overpotential of 214 and 659 mV at 10 and 500 mA cm-2, respectively (without IR correction), and high stability, which are much better than those of NiOxHy, NiFeOxHy and CeO2-NiOxHy. These findings provide an effective strategy to achieve the active metals with high-valence state for highly efficient OER.

Dynamic Redox Induced Localized Charge Accumulation Accelerating Proton Exchange Membrane Electrolysis

The sluggish anodic oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolysis necessitates applied bias to facilitate electron transfer as well as bond cleavage and formation. Traditional electrocatalysis focuses on analyzing the effects of electron transfer, while the role of charge accumulation induced by the applied overpotential has not been thoroughly investigated. To explore the influence mechanism of bias-driven charge accumulation, capacitive Mn is incorporated into IrO2 to regulate the local electronic structure and the adsorption behavior. The applied bias triggers dynamic redox reactions at the active sites, which introduce local charge accumulation on the surface of electrocatalyst. Under bias, Mn oxidation induced a noticeable pseudocapacitance in the pre-OER region, promoting the OER kinetics of iridium sites. Meanwhile, the increased oxygen vacancy formation energy further prevents the lattice oxygen activation. The PEM electrolyzer, equipped with optimal materials as an anode, operates at a low driving voltage of 1.637 V under 2.0 A cm-2, maintaining stable performance for over 800 h with a low degradation rate (19.4 µV h-1). This work provides insights into the performance of metal oxide catalysts in acidic environments and offers forward-looking strategies for enhancing the catalytic performance through dynamic redox induced capacitive behavior.

Regulating the 3d-orbital occupancy on Ni sites enables high-rate and durable Ni(OH)2 cathode for alkaline Zn batteries

The capacity and cycling stability of β-Ni(OH)2-based cathodes in aqueous alkaline Ni-Zn batteries are still unsatisfactory due to their undesirable OH- adsorption/desorption dynamics during the electrochemical redox process. To settle this issue, we introduce a new atomic-level strategy to finely modulate the OH- adsorption/desorption of β-Ni(OH)2 through tailoring the 3d-orbital occupancy of Ni center by Co/Cu co-doping (denoted as Co-Cu-Ni(OH)2). Both experimental outcomes and density functional theory calculations validate that the co-doping of Co and Cu endows the Ni species in Co-Cu-Ni(OH)2 with appropriate proportion of the unoccupied 3d-orbital, leading to optimized adsorption/desorption strength of OH-. As anticipated, the Co-Cu-Ni(OH)2 electrode demonstrates superior performance, achieving an areal capacity of 0.83 mAh cm-2 and a gravimetric capacity of 164.3 mAh g-1 at ∼50 mA cm-2 (10 A g-1). Furthermore, it sustains an impressive capacity of 170.8 mAh g-1 (2.3 mAh cm-2) at a high mass loading of 13.5 mg cm-2, alongside a long-term cycling performance over 1000 cycles. The assembled Co-Cu-Ni(OH)2//Zn cell is able to provide a peak energy density of 0.98 mWh cm-2 and excellent durability. This work highlights the potential of an orbital engineering strategy in the development of next-generation high-capacity and durable energy storage materials.

Modulation of Co spin state at Co3O4 crystalline-amorphous interfaces for CO oxidation and N2O decomposition

Modulation of electronic spin states in cobalt-based catalysts is an effective strategy for molecule activations. Crystalline-amorphous interfaces often exhibit unique catalytic properties due to disruptions of long-range order and alterations in electronic structure. However, the mechanisms of molecule activation and spin states at interfaces remain elusive. Herein, we present a Co3O4 spinel-based catalyst featuring crystalline-amorphous interfaces. Characterization analyses confirm that tetrahedral Co2+ is selectively etched from bulk spinel, forming amorphous CoO islands on the surface. The resultant symmetry breaking in the coordination field induces a reconstruction of the Co3+ 3 d orbitals, leading to high-spin states. In CO oxidation, the interface serves as novel active sites with a lower energy barrier, facilitated by lattice oxygen activation. In N2O decomposition, the interface promotes reassociation of dissociated oxygen through quantum spin exchange interactions. This work provides a straightforward approach to modulating the spin state of interfaces and elucidates their role in molecule activations.

Optimizing Nitrate Electroreduction toward Nearly 100% Ammonia Selectivity through Synergistic RuCu Catalysts and Integrated Coupled Anodic Reaction for High-Value Products

Copper-based catalysts have been widely used in the field of the nitrate reduction reaction (NO3RR) to ammonia, demonstrating high nitrate reduction rates. However, their low selectivity for ammonia production poses significant limitations in practical applications. In this study, we present that the incorporation of Ru into the Cu@Ni foam can achieve nearly 100% selectivity for NH3 and a high faradaic efficiency of 96.8% in the NO3RR. Ru not only facilitates the generation of adsorbed hydrogen but also suppresses the HER reaction. This can be attributed to the unique electron distribution exhibited by Ru atoms when surrounded by Cu, leading to a decreased electron-accepting capability. Consequently, this reduction results in a diminished Lewis acidity and a decreased H* adsorption. Importantly, it was confirmed that the incorporation of Cu with Ru serves as "anchor" for atomic H* generated from Ru, inhibiting HER and ensuring the availability of H* for subsequent ammonia production. The synergistic effect between Ru and Cu enhanced the efficiency and selectivity of reduction of nitrate to NH3. Remarkably, substituting oxygen evolution reaction (OER) with a coupled anodic reaction for the oxidation of benzyl alcohol to benzaldehyde can significantly accelerate the nitrate reduction rate by 1.7 times and achieves a 90% benzaldehyde conversion rate. This research not only introduces innovative strategies for designing high-performance ammonia-selective electrocatalysts but also highlights the potential industrial applications for the synthesis of high-value products.

Importing Atomic Rare-Earth Sites to Activate Lattice Oxygen of Spinel Oxides for Electrocatalytic Oxygen Evolution

Spinel oxides have emerged as highly active catalysts for the oxygen evolution reaction (OER). Owing to covalency competition, the OER process on spinel oxides often follows an arduous adsorbate evolution mechanism (AEM) pathway. Herein, we propose a novel rare-earth sites substitution strategy to tune the lattice oxygen redox of spinel oxides and bypass the AEM scaling relationship limitation. Taking NiCo2O4 as a model, the incorporation of Ce into the octahedral site induces the formation of Ce-O-M (M=Ni, Co) bridge, which triggers charge redistribution within NiCo2O4. The developed Ce-NiCo2O4 exhibits remarkable OER activity with a low overpotential, satisfactory electrochemical stability, and good practicability in anion-exchange membrane water electrolyzer. Theoretical analyses reveal that OER on Ce-NiCo2O4 surface follows a more favorable lattice oxygen mechanism (LOM) pathway and non-concerted proton-electron transfers compared to pure NiCo2O4, as also verified by pH-dependent behavior and in situ Raman analysis. The 18O-labeled electrochemical mass spectrometry provides direct evidence that the oxygen released during the OER originates from the lattice oxygen of Ce-NiCo2O4. We discover that electron delocalization of Ce 4f states triggers charge redistribution in NiCo2O4 through the Ce-O-M bridge, favoring antibonding state occupation of Ni-O bonding in [Ce-O-Ni] unit site, thereby activating lattice oxygen redox of NiCo2O4 in OER. This work provides a new perspective for designing highly active spinel oxides for OER and offers significant insights into the rare-earth-enhanced LOM mechanism.

Operando monitoring of the functional role of tetrahedral cobalt centers for the oxygen evolution reaction

The complexity of the intrinsic oxygen evolution reaction (OER) mechanism, particularly the precise relationships between the local coordination geometry of active metal centers and the resulting OER kinetics, remains to be fully understood. Herein, we construct a series of 3 d transition metal-incorporated cobalt hydroxide-based nanobox architectures for the OER which contain tetrahedrally coordinated Co(II) centers. Combination of bulk- and surface-sensitive operando spectroelectrochemical approaches reveals that tetrahedral Co(II) centers undergo a dynamic transformation into highly active Co(IV) intermediates acting as the true OER active species which activate lattice oxygen during the OER. Such a dynamic change in the local coordination geometry of Co centers can be further facilitated by partial Fe incorporation. In comparison, the formation of such active Co(IV) species is found to be hindered in CoOOH and Co-FeOOH, which are predominantly containing [CoIIIO6] and [CoII/FeIIIO6] octahedra, respectively, but no mono-μ-oxo-bridged [CoIIO4] moieties. This study offers a comprehensive view of the dynamic role of local coordination geometry of active metal centers in the OER kinetics.

Harnessing the Synergistic Interplay between Atomic-Scale Vacancies and Ligand Effect to Optimize the Oxygen Reduction Activity and Tolerance Performance

Defect engineering is an effective strategy for regulating the electrocatalysis of nanomaterials, yet it is seldom considered for modulating Pt-based electrocatalysts for the oxygen reduction reaction (ORR). In this study, we designed Ni-doped vacancy-rich Pt nanoparticles anchored on nitrogen-doped graphene (Vac-NiPt NPs/NG) with a low Pt loading of 3.5 wt . % and a Ni/Pt ratio of 0.038 : 1. Physical characterizations confirmed the presence of abundant atomic-scale vacancies in the Pt NPs induces long-range lattice distortions, and the Ni dopant generates a ligand effect resulting in electronic transfer from Ni to Pt. Experimental results and theoretical calculations indicated that atomic-scale vacancies mainly contributed the tolerance performances towards CO and CH3OH, the ligand effect derived from a tiny of Ni dopant accelerated the transformation from *O to *OH species, thereby improved the ORR activity without compromising the tolerance capabilities. Benefiting from the synergistic interplay between atomic-scale vacancies and ligand effect, as-prepared Vac-NiPt NPs/NG exhibited improved ORR activity, sufficient tolerance capabilities, and excellent durability. This study offers a new avenue for modulating the electrocatalytic activity of metal-based nanomaterials.

Built-in electric field guides oxygen evolution electrocatalyst reconstruction

Creating a built-in electric field (BIEF) in catalysts represents an effective strategy to promote electron transfer and induce asymmetric charge distribution, thereby facilitating surface dynamic reconstruction under oxygen evolution reaction (OER) conditions. This review summarizes recent advancements in the field of OER electrocatalysts, with a focus on regulating the work function of components to tailor the BIEFs to guide surface reconstruction processes. It also discusses the importance of surface reconstruction in improving electrocatalytic performance and the influence of BIEFs on the reconstruction of catalysts. By analyzing various strategies for manipulating electric fields for guiding surface reconstruction of OER electrocatalysts, along with numerous representative examples, this review highlights how these techniques can enhance catalytic activity and stability. The findings underscore the potential of engineered BIEFs as a powerful tool in the design of next-generation electrocatalysts, paving the way for more efficient energy conversion technologies.

Surface Cladding Engineering via Oxygen Sulfur Distribution for Stable Electrocatalytic Oxygen Production

Inevitable leaching and corrosion under anodic oxidative environment greatly restrict the lifespan of most catalysts with excellent primitive activity for oxygen production. Here, based on Fick' s Law, we present a surface cladding strategy to mitigate Ni dissolution and stabilize lattice oxygen triggering by directional flow of interfacial electrons and strong electronic interactions via constructing elaborately cladding-type NiO/NiS heterostructure with controlled surface thickness. Multiple in situ characterization technologies indicated that this strategy can effectively prevent the irreversible Ni ions leaching and inhibit lattice oxygen from participating in anodic reaction. Combined with density functional theory calculations, we reveal that the stable interfacial O-Ni-S arrangement can facilitate the accumulation of electrons on surficial NiO side and weaken its Ni-O covalency. This would suppress the overoxidation of Ni and simultaneously fixing the lattice oxygen, thus enabling catalysts with boosted corrosion resistance without sacrificing its activity. Consequently, this cladding-type NiO/NiS heterostructure exhibits excellent performance with a low overpotential of 256 mV after 500 h. Based on Fick's law, this work demonstrates the positive effect of surface modification through precisely adjusting of the oxygen-sulfur exchange process, which has paved an innovative and effective way to solve the instability problem of anodic oxidation.

Tracking the correlation between spintronic structure and oxygen evolution reaction mechanism of cobalt-ruthenium-based electrocatalyst

Regulating the spintronic structure of electrocatalysts can improve the oxygen evolution reaction performance efficiently. Nonetheless, the effects of tuning the spintronic structure for the oxygen evolution reaction mechanisms have rarely been discussed. Here, we show a ruthenium-cobalt-tin oxide with optimized spintronic structure due to the quantum spin interaction of Ru and Co. The specific spintronic structure of ruthenium-cobalt-tin oxide promotes the charge transfer kinetics and intermediates evolution behavior under applied potential, generating long-lived active species with higher spin density sites for the oxygen evolution reaction after the reconstruction process. Moreover, the ruthenium-cobalt-tin oxide possesses decoupled proton-electron transfer procedure during the oxygen evolution reaction process, demonstrating that the electron transfer procedure of O-O bond formation between *O intermediate and lattice oxygen in Co-O-Ru is the rate-determining step of the oxygen evolution reaction process. This work provides rational perspectives on the correlation between spintronic structure and oxygen evolution reaction mechanism.