Reversible hydrogen spillover in Ru-WO3-x enhances hydrogen evolution activity in neutral pH water splitting

Tailored electronic interaction between metal-support trigger reverse hydrogen spillover for efficient hydrogen evolution

The triggering of fast hydrogen spillover through regulating the charge rearrangement of the metal-support serves as a crucial mechanism for decoupling the activity of HER catalysts from the adsorption properties, which not only contributes to enhancing the performance of the catalysts but also facilitates the production of green hydrogen. Herein, we tailor the electronic interaction between two-dimensional (2D) nitrogen-doped MoC (N-MoC) nanosheets and anultra-low content of Pt nanoclusters (1 wt%) to trigger reverse hydrogen spillover and modulate the electronic structure of Pt, thus achieving efficient and stable HER. Compared to Pt/C (0.229 A mgPt-1), Pt/N-MoC demonstrates a mass activity of 12.945 A mgPt-1, representing an enhancement of nearly 57.5 times. Notably, the excellent electrocatalytic performance was verified in the proton exchange membrane water electrolyzer configuration. Combining experimental and theoretical analysis, anultra-low load of Pt nanocluster (1 wt%) integrated with N-MoC nanosheets can induce a charge transfer from N-MoC to Pt, thus modulating the d-band center of Pt to improve the hydrogen adsorption properties and achieving fast hydrogen desorption (ΔG = 0.019 eV); furthermore, a small difference in work function between Pt nanoclusters and the N-MoC were achieved to dilute charge accumulation between the metal-support interface, thus reducing the energy barrier of hydrogen spillover.

Closed-Loop Framework for Discovering Stable and Low-Cost Bifunctional Metal Oxide Catalysts for Efficient Electrocatalytic Water Splitting in Acid

Electrocatalytic water splitting, comprising the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), provides a sustainable route for hydrogen production. While low-cost metal oxides (MOs) are appealing as alternatives to noble metal electrocatalysts, their application in acidic media remains challenging. However, the dynamic nature of some MO surface structures under electrochemical conditions offers an opportunity for rational catalyst design to achieve bifunctionality in acidic OER and HER. Here, we present a closed-loop framework that integrates potential catalyst exploration (front-end), synthesis and electrochemical tests (mid-end), and advanced characterizations (back-end). This framework combines crucial steps in electrocatalyst exploration, including data mining, surface state analysis, microkinetic modeling, and proof-of-concept experiments to identify stable and cost-effective MO catalysts for acidic water splitting. Using this approach, RbSbWO6 is identified as a promising bifunctional catalyst for the first time, with experimental validation demonstrating its exceptional stability and performance under acidic OER and HER. Notably, RbSbWO6 outperforms many other reported non-noble stoichiometric MO catalysts that have not undergone major modifications for acidic water splitting. These findings, derived from our Digital Catalysis Platform (DigCat), establish RbSbWO6 as a highly effective non-noble stoichiometric bifunctional MO catalyst and underscore the power of our closed-loop workflow for accelerating catalyst discovery. This framework begins with the DigCat platform, concludes with experimental validation, and feeds into the platform, demonstrating its potential for designing electrocatalysts in other systems such as metal nitrides or carbides. This study demonstrates the importance and high efficiency of data-driven approaches as a new scientific discovery paradigm.

Abundant Amorphous/Crystalline Interfaces of C/A-NixP/NiOH Heterojunction Catalyst for Efficient Urea Oxidation Reaction

Replacing the kinetically slow oxygen evolution reaction (OER) with urea electro-oxidation significantly reduces the energy requirement for electrolysis of water. However, designing and optimizing efficient electrocatalysts for the industrial application of urea oxidation coupled to hydrogen production remains a challenge. Herein, we construct a C/A-NixP/NiOH heterojunction catalyst with actually abundant amorphous/crystalline interfaces for the urea oxidation reaction (UOR) by an interfacial-sequential treatment method of electrodeposition and low-temperature gas-phase phosphatization on carbon cloth (CC). Remarkably, in UOR, the C/A-NixP/NiOH catalyst required only 1.332 V to reach a current density of 10 mA cm-2 with negligible potential decay over 12 h. The excellent performance is attributed to the synergistic interaction between the inner amorphous NiOH layer and the outer crystalline NixP layer, as well as the abundant amorphous/crystalline interface, an interfacial structure that can expose more active sites as well as enhance the intrinsic activity, thus improving the reaction kinetics and stability of UOR. This work paves the way for the development of low-cost and high-efficiency catalysts for urea oxidation.

Built-in Electric Field in Ru/CoP Bifunctional Electrocatalyst Enhances Hydrazine-Assisted Water Splitting

Electrocatalytic hydrazine-assisted water splitting, incorporating the hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR), offers a promising avenue for hydrogen production. Herein, a Ru/CoP heterostructure is introduced, which enhances bifunctional catalytic activity through interfacial interaction induced by the built-in electric field between Ru nanoparticles and CoP nanosheets. This interaction optimizes the adsorption of intermediates and facilitates improved HER performances by weakening the strong adsorption of active hydrogen species (*H) on Ru and enhancing *H coverage on CoP through hydrogen spillover. Additionally, this electron interaction promotes the adsorption of N2H4 and its subsequent dehydrogenation, vital for HzOR activity. The heterostructure's significant reduction in required potentials for both reactions underscores its efficiency and potential economic benefits over traditional systems. Furthermore, the study validates the feasibility of using this approach for practical applications in sustainable hydrogen production, emphasizing its lower operational costs and enhanced catalytic stability and activity. This work not only showcases the practical applications of Ru/CoP but also underscores the broader applicability of heterostructure strategy in designing efficient bifunctional electrocatalysts.

Heterogeneous Interfaces of Ni3Se4 Nanoclusters Decorated on a Ni3N Surface Enhance Efficient and Durable Hydrogen Evolution Reactions in Alkaline Electrolyte

Transition metal selenides (TMSes) have been identified as cost-efficient alternatives to platinum (Pt) for the alkaline hydrogen evolution reaction (HER) owing to their distinct electronic properties and excellent conductivity. However, they encounter challenges such as sluggish water dissociation and severe oxidative degradation, requiring further optimizations. In this study, we developed a dual-site heterogeneous catalyst, Ni3Se4-Ni3N, by decorating Ni3Se4 nanoclusters on a Ni3N substrate. This catalyst design promoted significant interfacial electronic interactions, modulated electronic structures, and enhanced the adsorption of the intermediates. Various spectroscopic analyses and theoretical calculations revealed that the nitride surfaces improved water adsorption and dissociation, enriching the surface with adsorbed hydrogen (H*) atoms, while the Se sites facilitated hydrogen coupling and subsequent release of H2. Following a hydrogen spillover mechanism, the surface-adsorbed hydrogen atoms were transferred to nearby electron-dense selenide sites for H2 formation and release. Consequently, the optimized catalyst demonstrated improved HER activity, requiring only an ∼60 mV overpotential at 10 mA cm-2 current density and maintained stability under higher potential conditions.

Recent Advances in Functionalizing Metal Oxide Semiconductors for Highly Sensitive Gas Sensors

Metal oxide semiconductors (MOSs) have emerged as pivotal materials for gas sensing technologies due to their inherent advantages, including cost-effectiveness, simplicity in synthesis, and easy fabrication of sensing nanodevices. These characteristics have made MOSs widely applicable in industrial, environmental, and biological monitoring. While MOSs offer intrinsic gas-sensing properties, their limited active site density and function diversity restrict sensitivity and selectivity, especially in complex gaseous environments. To overcome these limitations, extensive research efforts have been devoted to functionalizing MOSs through strategies such as heterojunction construction, noble metal nanoparticle loading (e.g., Au, Pt, Ag, Pd), and heteroatom doping (e.g., Si, Cr). Furthermore, composite materials have emerged as an effective approach to enhance MOSs-based gas sensors by integrating carbon-based materials or polymers to leverage synergistic interactions. These modifications expand the applicability of MOSs sensors for detecting volatile organic compounds, toxic gases, and flammable gases. This review systematically examines the synthesis strategies and performance enhancements achieved through MOSs functionalization and composite material integration, emphasizing structure-property relationships, interfacial charge transfer dynamics, and adsorption mechanisms. Finally, the challenges and future directions for the rational design of next-generation MOSs-based gas sensors are outlined, providing critical insights for advancing intelligent gas sensing technologies.

Lattice coherency engineering trigger rapid charge transport at the heterointerface of Te/In2O3@MXene photocatalysts for boosting photocatalytic hydrogen evolution

The establishment of heterojunctions has been demonstrated as an effective method to improve the efficiency of photocatalytic hydrogen production. Conventional heterojunctions usually have random orientation relationships, and heterointerfaces can hinder photogenerated carrier transport due to larger lattice mismatches, thus reducing the photoelectric conversion efficiency. In this study, a novel Te/In2O3@MXene lattice coherency heterojunction was prepared by leveraging the identical lattice spacing of In2O3 (222) and Te (021) crystal face. The lattice consistency facilitates enhanced photogenerated carrier transport rate between the heterostructure interface of In2O3 and Te. Furthermore, the incorporation of MXene, the electrons originating from Te 5p orbital achieve directional transfer in the heterojunction. This reduces the recombination of photogenerated electron - hole pairs and retains the photogenerated electrons with higher reducibility. The hydrogen production efficiency of Te/In2O3@MXene is 568.8 μmol/h g-1, which is 24 times higher than that of pristine In2O3, and it remains 90 % of its initial activity after six cycles. This study offers a novel approach to address the escalating carrier transfer resistance commonly observed in conventional heterojunctions.

Breaking Linear Scaling Relation Limitations on a Dual-Driven Single-Atom Copper-Tungsten Oxide Catalyst for Ammonia Synthesis

Electrocatalytic reduction of nitrate (NO3 -, NO3RR) on single-atom copper catalysts (Cu-SACs) offers a sustainable approach to ammonia (NH3) synthesis using NO3 - pollutants as feedstocks. Nevertheless, this process suffers from inferior NO3RR kinetics and nitrite accumulation owing to the linear scaling relation limitations for SACs. To break these limitations, a single-atom Cu-bearing tungsten oxide catalyst (Cu1/WO3) was developed, which mediated a unique dual-driven NO3RR process. Specifically, WO3 dissociated water molecules and supplied the Cu1 site with ample protons, whereas the Cu1 site in an electron-deficient state converted NO3 - to NH3 efficiently. The Cu1/WO3 delivered an impressive NH3 production rate of 1274.4 mgN h-1 gCu -1, a NH3 selectivity of 99.2%, and a faradaic efficiency of 93.7% at -0.60 V, surpassing most reported catalysts. Furthermore, an integrated continuous-flow system consisting of a NO3RR cell and a vacuum-driven membrane separator was developed for NH3 synthesis from nitrate-contaminated water. Fed with the Yangtze River water containing ∼22.5 mg L-1 of NO3 --N, this system realized an NH3 production rate of 325.9 mgN h-1 gCu -1 and a collection efficiency of 98.3% at energy consumption of 17.11 kwh gN -1. This study provides a new dual-driven concept for catalyst design and establishes a foundation for sustainable NH3 synthesis from waste.

Size Effect of Surface Defects Dictates Reactivity for Nitrogen Electrofixation

Electrocatalytic nitrogen reduction reaction (eNRR) offers a sustainable pathway for ammonia (NH3) production. Defect engineering enhances eNRR activity but can concurrently amplify the competing hydrogen evolution reaction (HER), posing challenges for achieving high selectivity. Herein, VOx with systematically tuned defect sizes is engineered to establish a structure-activity relationship between defect size and eNRR performance. In situ spectroscopy and theoretical calculations reveal that medium-sized defects (VOx-MD, 1-2 nm) provide an optimal electronic environment for enhanced N2 adsorption and activation while maintaining spatial flexibility to facilitate efficient hydrogenation. Consequently, VOx-MD exhibits outstanding eNRR performance, achieving an NH3 yield rate of 81.94 ± 1.45 µg h-1 mg-1 and a Faradaic efficiency of 31.97 ± 0.75 % at -0.5 V (vs RHE). These findings highlight the critical role of defect size in governing eNRR activity, offering a scalable strategy for designing advanced catalysts for competitve electrocatalytic reactions.

Short-Path Hydrogen Spillover on CeO2-Supported PtPd Nanoclusters for Efficient Hydrogen Evolution in Acidic Media

Hydrogen spillover in supported metal electrocatalysts has garnered significant research attention for its potential to enhance the hydrogen evolution reaction (HER) efficiency. However, challenges remain in facilitating hydrogen spillover and reducing the associated energy barriers. Herein, PtPd alloy clusters are anchored to the CeO2 surface, enabling short-path hydrogen spillover and lowering the reaction energy barrier in acidic environments. During HER, hydrogen is initially adsorbed on the noble metal surface and subsequently migrates to the interface, rather than precipitating directly on the CeO2 surface. This interface exhibits a near-zero Gibbs free energy of hydrogen adsorption (0.023 eV). Consequently, the catalyst demonstrates an exceptionally low overpotential of only 5.7 mV at 10 mA cm-2 in acidic media, along with remarkable long-term stability. These findings provide valuable insights into designing highly efficient HER electrocatalysts for acidic environments based on hydrogen spillover mechanisms.

Visualization of the Key Proton Activities in Hydrogen Evolution Reaction by Electrochromic Catalyst

The electrocatalytic hydrogen evolution reaction (HER) is a promising route to produce sustainable hydrogen energy carrier for global carbon neutrality. The HER performance is largely determined by the overall proton activities, but the identification of such key proton activities in microscopic HER process is rather difficult. Herein, the study demonstrates a visualized HER concept by integrating the fundamental HER process with electrochromic technology on a well-designed Pt@WO3 platform in acidic electrolyte, where the overall proton activities in HER process can be rapidly discriminated by the color changes of Pt@WO3 electrochromic electrode. In contrast to bare WO3 counterpart, the Pt@WO3 electrochromic electrode displays a rather more positive potential of initial-coloration state and faster decoloration rate associated with significantly improved reaction kinetics of hydrogen intercalation and deintercalation within WO3 component. Correspondingly, the as-prepared Pt@WO3 catalyst electrode exhibits a remarkable HER activity with a lower onset-potential (45 mV, proton adsorption and accumulation) and smaller Tafel slope (50 mV dec-1, proton desorption), nearly 11.1- and 3.5-fold enhancement than those of bare WO3 counterpart. It is believed that the work in integrating the interesting visualization functionality into fundamental HER process may improve the readability of such microscopic electrocatalytic reaction and advance the exploration of more intelligent electrocatalysts.

Enhancing Built-In Electric Field via Balancing Interfacial Atom Orbit Hybridization at Boride@Sulfide Heterostructure for Hydrogen Evolution Reaction

Exploring nonprecious metal-based catalysts for cathodic hydrogen evolution reaction (HER) has facilitated the realization of hydrogen economy toward water electrolysis in alkaline media. However, the difficult water dissociation process for the Volmer step (H2O → H* + OH*) and the subsequent unsuitable OH* adsorption energy on nonprecious metal-based catalysts severely reduce the kinetics of HER. Herein, the universal synthesis for a series of transition metal (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W)-based boride@sulfide heterostructured catalysts is realized by using the molten-salt method to conduct the in situ boronization of commercial sulfides. Significantly, WB2@WS2 heterostructured catalyst exhibits excellent catalytic activity and stability for HER. Balancing interfacial atom orbit hybridization between W(d)-B(s,p) and W(d)-S(s,p) at WB2@WS2 heterostructured interface enhances the built-in electric field. In situ Raman spectroscopy and density functional theory calculation results reveal that the strong built-in electric field in WB2@WS2 optimizes the adsorption and desorption of OH* intermediate, reducing the energy barrier of the rate-determining step (OH* desorption step), and thus favoring the enhancement of catalytic performance toward HER.

Advanced Fabrication of Graphene-Integrated High-Entropy Alloy@Carbon Nanocomposites as Superior Multifunctional Electrocatalysts

High entropy materials exhibit unparalleled reactivity and tunable electrochemical properties, putting them at the forefront of advances in electrocatalysis for water splitting. Their various interfaces and elements are purposefully engineered at the nanoscale, which is essential to enhancing their electrochemical characteristics. The exceptional catalytic efficiency observed in graphene-coated nanoparticles (NPs) with an inner high-entropy alloy (HEA) (HEA@C) is a result of the combined action of several metallic constituents. However, increasing catalytic efficiency is still a very difficult task, particularly when it comes to obtaining precise control over the composition and structure via efficient synthesis techniques. HEA@C NPs exceptional reactivity and adaptable electrochemical characteristics allow them to perform better in slow oxygen evolution (SOE) activities. The novel multilayer graphene-enhanced HEA CoNiFeCuV@C NPs electrocatalyst presented in this work is carbon-based, and transmission electron microscopy (TEM) investigations verify its efficacy. The efficiency of the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) is greatly increased by this electrocatalyst. The electrocatalytic performance of the core-shell HEA CoNiFeCuV@C NPs is remarkable for HER, OER, and ORR, even though its highly stressed lattice has structural flaws. These catalysts reach a half-wave potential of 0.87 V in 0.1 M HClO4 at a moderate current density of 10 mA cm-2, with HER and OER onset potentials of 20 and 259 mV, respectively. Using cyclic voltammetry scans, the study delves deeper into the material's evolution by examining its morphology, chemical state, and elemental makeup both before and after activation. In addition to introducing novel electrocatalysts, this study significantly enhances our understanding of the deliberate synthesis of multicomponent intermetallic high-entropy alloys.

Valence State Hydrogen Channel Enhances Sustained and Controllable Electrocatalytic Hydrogen Evolution in Diabetic Skin Wound Healing

Diabetes significantly increases the risk of serious health issues, including prolonged skin inflammation and delayed wound healing, owing to inferior glucose control and suppression of the immune system. Although traditional hydrogen (H2) therapy is slightly effective, its ability to tailor the release of H2 on the skin is limited. Accordingly, this study proposed a novel strategy for electrocatalytic H2 release under neutral conditions to promote wound healing in diabetic mice and rabbit. Herein, a defect-engineered cobalt phosphide (CoP) catalyst was designed by introducing a neutral single-metal electrocatalytic Hydrogen valence state channel into CoP. By effectively regulating the formation and transfer of *H active species during the CoP catalytic process, a considerable enhancement in neutral electrocatalytic H2 evolution performance was achieved (-78.0 mV@-10.0 mA cm-2). Based on this superior catalytic performance, we developed a flexible electrode (namely, CoP/flexible gold electrode made by screen printing (FGSP) by combining a convenient electrolysis platform with continuous electrolyte supply and FGSP, enabling customized H2 release and accelerating wound healing in diabetic mice and rabbits. Notably, the designed flexible electrode features adjustable dimensions, interchangeable substrates, and material adaptability, meeting the diverse needs of clinical and basic research and demonstrating significant potential for applications in clinical medicine.

Negative-Valent Platinum Stabilized by Pt─Ni Electron Bridges on Oxygen-Deficient NiFe-LDH for Enhanced Electrocatalytic Hydrogen Evolution

The unique hydrogen adsorption characteristics of negatively charged platinum play a crucial role in enhancing the electrocatalytic hydrogen evolution reaction. However, atomically dispersed Pt atoms are typically anchored to the support through non-metallic atom bonds, resulting in a high oxidation state. Here, atomically dispersed Pt atoms are anchored in oxygen-deficient NiFe-LDH. Electron transfer between Pt and NiFe-LDH occurs primarily through Pt─Ni bonds rather than the conventional Pt─O bonds. Oxygen vacancies in the NiFe-LDH promote additional electron transfer from Ni to Pt, thereby reducing the valence state of Pt and enhancing hydrogen adsorption. Meanwhile, the elevated valence state of Ni increases the catalyst's hydrophilicity and reduces the energy barrier for hydrolysis dissociation. This catalyst demonstrates remarkably low overpotentials of 4 and 9 mV at 10 mA cm-2 in 1 m KOH and 1 m KPi, respectively. Additionally, its mass activity is 51.5 and 23.7 times higher that of Pt/C, respectively. This study presents a novel strategy for enhancing electrocatalytic performance through the rational design of coordination environments and electronic structures in supported metal catalysts.

Promoting Efficient Ruthenium Sites With Lewis Acid Oxide for the Accelerated Hydrogen and Chlor-Alkali Co-Production

Ruthenium (Ru) -based catalysts have been considered a promising candidate for efficient sustainable hydrogen and chlor-alkali co-production. Theoretical calculations have disclosed that the hollow sites on the Ru surface have strong adsorption energies of H and Cl species, which inevitably leads to poor activity for cathodic hydrogen evolution reaction (HER) and anodic chlorine evolution reaction (CER), respectively. Furthermore, it have confirmed that anchoring Lewis acid oxide nanoparticles such as MgO on the Ru surface can induce the formation of the onion-like charge distribution of Ru atoms around MgO nanoparticles, thereby exposing the Ru-bridge sites at the interface as excellent H and Cl adsorption sites to accelerate both HER and CER. Under the guidance of theoretical calculations, a novel dispersed MgO nanoparticles on Ru (MgOx-Ru) electrocatalyst is successfully prepared. In strongly alkaline and saline media, MgOx-Ru recorded excellent HER and CER electrocatalytic activity with a very low overpotential of 19 mV and 74 mV at the current density of 10 mA cm-2, respectively. More stirringly, the electrochemical test with MgOx-Ru as both anodic and cathodic electrodes under simulated chlor-alkali electrolysis conditions demonstrated superior electrocatalytic performance to the industrial catalysts of commercial 20 wt% Pt/C and dimensionally stable anode (DSA).

Surface Reconstruction of An Integrated CoO-Co2Mo3O8 Electrode Enabling Efficient Ampere-Level Hydrogen Evolution in Alkaline Water or Seawater

To accelerate the water dissociation in the Volmer step and alleviate the destruction of bubbles to the physical structure of catalysts during the alkaline hydrogen evolution, an integrated electrode of cobalt oxide and cobalt-molybdenum oxide grown on Ni foam, named CoO-Co2Mo3O8, is designed. This integrated electrode enhances the catalyst-substrate interaction confirmed by a micro-indentation tester, and thus hinders the destruction of the physical structure of catalysts caused by bubbles. Electrochemical testing shows the occurrence of a surface reconstruction of the integrated electrode, and CoO is transformed into Co(OH)2, denoted as Co(OH)2-Co2Mo3O8. Theoretical calculations determine that Co(OH)2-Co2Mo3O8 has significantly low activation barrier for water dissociation and presents easy hydroxide desorption, which accelerate the catalytic reaction. Electrochemical experiments show that Co(OH)2-Co2Mo3O8 exhibits outstanding activity, reaching current density values of -100 and -1000 mA cm-2 with overpotentials only 57.8 and 195.8 mV, respectively. Furthermore, it demonstrates excellent stability at -500 and -1000 mA cm-2 for 200 h. Combined with the previously reported anode, the two-electrode system also provides the stable operation from 100 to 1000 mA cm-2 for 600 h in alkaline solution, and over 200 h at 500 and 1000 mA cm-2 in alkaline seawater.

Electrocatalytic Hydrogenation Boosted by Surface Hydroxyls-Modulated Hydrogen Migration over Nonreducible Oxides

The migration of atomic hydrogen species over heterogeneous catalysts is deemed essential for hydrogenation reactions, a process closely related to the catalyst's functionalities. While surface hydroxyls-assisted hydrogen spillover is well documented on reducible oxide supports, its effect on widely-used nonreducible supports, especially in electrocatalytic reactions with water as the hydrogen source, remains a subject of debate. Herein, a nonreducible oxide-anchored copper single-atom catalyst (Cu1/SiO2) is designed and uncover that the surface hydroxyls on SiO2 can serve as efficient transport channels for hydrogen spillover, thereby enhancing the activated hydrogen coverage on the catalyst and favoring the hydrogenation reaction. Using electrocatalytic dechlorination as a model reaction, the Cu1/SiO2 catalyst delivers hydrodechlorination activity 42 times greater than that of commercial Pd/C. An integrated experimental and theoretical investigation elucidates that surface hydroxyls facilitate the spillover of hydrogen intermediates formed at the Cu sites, boosting the coverage of active hydrogen on the surface of the Cu1/SiO2. This work demonstrates the feasibility of surface hydroxyls acting as transport channels for hydrogen-species to boost hydrogen spillover on nonreducible oxide supports and paves the way for designing advanced selective hydrogenation electrocatalysts.

Ultrafast Synthesis of Nanoscale Metal Borides for Efficient Hydrogen Evolution

Nanoscale metal borides, with exceptional physicochemical properties, have been attracted widespread attention. However, traditional synthesis methods of metal borides often lead to surface coking and large particle sizes. Herein, we have employed a flash Joule heating (FJH) technique to enable the ultrafast synthesis of metal boride nanomaterials. The synthesized materials encompass a wide range of diverse categories, including alkaline-earth metal borides (CaB6), transition metal borides (TiB2, VB2, CrB2, MoB, MoB2, MnB2, MnB4, FeB, CoB, NiB), noble-metal borides (RuB2, RuB1.1), and rare-earth metal borides (LaB6, CeB6). As an example, the RuB2 demonstrates highly desirable electrocatalytic performance for all-pH hydrogen evolution reaction (HER). Especially, under the acidic condition, it exhibits an overpotential as low as 15 mV at a current density of 10 mA cm-2, with a nearly 100 % faradic efficiency. Additionally, in situ Raman spectra confirm that both Ru and B sites serve as active sites for the HER. Moreover, the stability of RuB2 can be further enhanced by optimizing the microenvironments of the anolyte composition (H+, K+). More importantly, the experimental and density functional theory (DFT) calculations reveal that the co-existence of H+ and K+ localized around the RuB2 plays a crucial role in further enhancing the stability.

Recent achievements in noble metal-based oxide electrocatalysts for water splitting

The search for sustainable energy sources has accelerated the exploration of water decomposition as a clean H2 production method. Among the methods proposed, H2 production via water electrolysis has garnered considerable attention. However, the process of H2 production from water electrolysis is severely limited by the slow kinetics of the anodic oxygen evolution reaction and large intrinsic overpotentials at the anode; therefore, suitable catalysts need to be found to accelerate the reaction rate. Noble metal-based oxide electrocatalysts retain the advantages of abundant active sites, high electrical conductivity of noble metals, and low cost, which make them promising electrocatalysts; however, they suffer from the challenge of an imbalance between catalytic activity and stability. This review presents recent research progress in noble metals and their oxides as electrocatalysts. In this review, two half-reactions (the hydrogen evolution reaction and the oxygen evolution reaction) of water electrolysis are described. Recently reported methods for the synthesis of noble metal-based oxide electrocatalysts, improvement strategies, and sources of enhanced activity and stability for these types of catalysts are presented. Finally, the challenges and future perspectives in the field are summarised. This review is expected to help improve the understanding of noble metal-based oxide electrocatalysts.

Tailoring Lewis Acidity of Metal Oxides on Nickel to Boost Electrocatalytic Hydrogen Evolution in Neutral Electrolyte

Neutral-pH water splitting for hydrogen production features a benign environment that could alleviate catalyst and electrolyzer corrosion but calls for the corresponding high-efficiency and earth-abundant hydrogen evolution reaction (HER) catalysts. Herein, we first designed a series of metal oxides decorated on Ni as the model catalysts and found a volcano-shaped relationship between the Lewis acidity of Ni/metal oxides and HER activity in neutral media. The Ni/ZnO with the optimum Lewis acidity could balance water dissociation and hydroxyl desorption, thereby greatly boosting the HER. On the basis of this finding, we further in situ grew the Ni/ZnO heterostructure on a three-dimensional conductive support. The resulting catalyst requires overpotentials of merely 34 and 194 mV to deliver the current densities of 10 and 200 mA cm-2, respectively, and can stably operate at these current densities for 2000 h in 1 M phosphate buffer solution (pH 7), representing the most active and durable HER catalyst in neutral electrolyte reported thus far. Our work provides an effective design scheme for low-cost and high-performance neutral HER catalysts.

Fabricating Lattice-Confined Pt Single Atoms With High Electron-Deficient State for Alkali Hydrogen Evolution Under Industrial-Current Density

The confining effect is essential to regulate the activity and stability of single-atom catalysts (SACs), but the universal fabrication of confined SACs is still a great challenge. Here, various lattice-confined Pt SACs supported by different carriers are constructed by a universal co-reduction approach. Notably, Pt single atoms confined in the lattice of Ni(OH)2 (Pt1/Ni(OH)2) with a high electron-deficient state exhibit excellent activity for basic hydrogen evolution reaction (HER). Specifically, Pt1/Ni(OH)2 just requires 15 mV to get 10 mA cm-2 and the mass activity of Pt1/Ni(OH)2 is 15 times of commercial Pt/C. Moreover, Pt1/Ni(OH)2 assembled in an alkaline water electrolyzer shows 1030 h durability under the industrial current density of 800 mA cm-2. In situ spectroscopy techniques reveal Pt─H and "free" OH radical can be directly observed for Pt1/Ni(OH)2, confirming the lattice-confined Pt single atoms play a key role during HER. Further density functional theory uncovers the Pt 3d orbital strongly hybridizes with O 2p and Ni 3d orbitals in Ni(OH)2, which quickly optimizes the electronic state of the Pt site, thus largely reducing the energy barrier of the rate-determining step to 0.16 eV for HER. Finally, this synthesis method is extended to construct other 9 lattice-confined SACs.

High-Performance Bi-Based Catalysts for CO₂ Reduction: In Situ Formation of Bi/Bi₂O₂CO₃ and Enhanced Formate Production

The unavoidable self-reduction of Bismuth (Bi)-based catalysts to zero-valence Bi often results in detrimental adsorption of OCHO*, leading to unsatisfactory selectivity of HCOOH in the electroreduction of carbon dioxide (CO2). A novel Bi-tannin (Bi-TA) complex is developed, which undergoes in situ reconstruction into a Bi/Bi₂O₂CO₃ phase during CO2 reduction. This reconstructed catalyst exhibits high activity and selectivity, achieving a Faradaic Efficiency (FE) for formate production exceeding 90%, peaking at 96%. Operando spectroscopic and theoretical analyses reveal that the Biδ+ active site in Bi/Bi₂O₂CO₃ significantly enhances the formation of the OCHO* intermediate, crucial for formate production. The study offers a promising approach to overcoming the limitations of Bi-based catalysts in CO2 reduction to formate.

Controllable Detachment of Organic Ligands on Ultrathin Amorphous Nanosheets Tailors the Electron-Aggregation for Accelerated pH-Universal Hydrogen Reaction

Tailoring the local environment of catalyst surface has emerged as an effective strategy to enhance the reaction kinetics involving multiple intermediates. For hydrogen evolution reactions (HER), the driving factors for hydrogen aggregation and migration which are poorly understood in depth affects the reaction kinetics especially over a wide pH range. Inspired by the selectivity of the catalyst surface microenvironment for intermediates, an interfacial electrocatalyst composed of Ru ultrafine nanocatalysts anchored onto monolayer amorphous (a-WCoNiO) nanosheets with electron-rich microenvironment induced by an organic oleylamine ligand is designed to realize high-performance pH-universal HER. This Ru/a-WCoNiO possesses impressively low overpotentials of -13, -14, and -14 mV at 10 mA cm-2 in 0.5 m H2SO4, 1 m KOH and 1 m PBS, respectively, ranking among the best HER catalysts reported to date. Benefiting from the electron-rich microenvironment, the Ru/a-WCoNiO exhibits record-high turnover frequency (TOF) and mass activity (MA), which is more than 47.9 times higher than that of commercial 20% Pt/C. Importantly, other precious metals are loaded on a-WCoNiO and enhancing their mass current density for pH-universal HER. It is believed that this developed approach of organic modifiers tailored local microenvironment has practical significance and advantages for designing other high-performance catalysts.

Isotopic labelling of water reveals the hydrogen transfer route in electrochemical CO2 reduction

Understanding the hydrogenation pathway in electrochemical CO2 reduction is important for controlling product selectivity. The Eley-Rideal mechanism involving proton-coupled electron transfer directly from solvent water is often considered to be the primary hydrogen transfer route. However, in principle, hydrogenation can also occur via the Langmuir-Hinshelwood mechanism using surface-adsorbed *H. Here, by performing CO2 reduction with Cu in H2O-D2O mixtures, we present evidence that the Langmuir-Hinshelwood mechanism is probably the dominant hydrogenation route. From this, we estimate the extent to which each mechanism contributes towards the formation of six important CO2 reduction products. Through computational simulations, we find that the formation of C-H bonds and O-H bonds is governed by the Langmuir-Hinshelwood and Eley-Rideal mechanism, respectively. We also show that promoting the Eley-Rideal pathway could be crucial towards selective multicarbon product formation and suppressing hydrogen evolution. These findings introduce important considerations for the theoretical modelling of CO2 reduction pathways and electrocatalyst design.

Operando Unveiling of Hydrogen Spillover Mechanisms on Tungsten Oxide Surfaces

Hydrogen spillover is an important process in catalytic hydrogenation reactions, facilitating H2 activation and modulating surface chemistry of reducible oxide catalysts. This study focuses on the operando unveiling of platinum-induced hydrogen spillover on monoclinic tungsten trioxide (γ-WO3), employing ambient pressure X-ray photoelectron spectroscopy, density functional theory calculations and microkinetic modeling to investigate the dynamic evolution of surface states at varied temperatures. At room temperature, hydrogen spillover results in the formation of W5+ and hydrogen intermediates (hydroxyl species and adsorbed water), facilitated by Pt metal clusters. With increasing temperature, water desorption, reverse hydrogen spillover and surface-to-bulk diffusion of hydrogen atoms compete with each other, leading initially to reoxidation and then further reduction of W atoms in the near-surface. The combined experimental results and simulations provide a comprehensive understanding of the mechanisms underlying hydrogen interaction with reducible metal oxides, lending insights of relevance to the design of enhanced hydrogenation catalysts.

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.

Unravelling the pH-dependent mechanism of ferroelectric polarization on different dynamic pathways of photoelectrochemical water oxidation

Ferroelectric polarization is considered to be an effective strategy to improve the oxygen evolution reaction (OER) of photoelectrocatalysis. The primary challenge is to clarify how the polarization field controls the OER dynamic pathway at a molecular level. Here, electrochemical fingerprint tests were used, together with theoretical calculations, to systematically investigate the free energy change in oxo and hydroxyl intermediates on TiO2-BaTiO3 core-shell nanowires (BTO@TiO2) upon polarization in different pH environments. We demonstrate that the adsorbate evolution mechanism (AEM) dominated in acidic environments, and both positive and negative polarization resulted in a reduction in the oxo-free energy, which inhibited the reaction kinetics. In the oxide path mechanism (OPM) that occurs in alkaline conditions, the ferroelectric polarization exhibits repulsive adsorbate-adsorbate interaction for OH- coverage and free energy shift of the OH- groups. We elucidate that a weakly alkaline electrolyte is the optimal environment for ferroelectric polarization because the positive polarization promotes OH- coverage and facilitates reaction pathway transfer from AEM to OPM; therefore, BTO@TiO2 exhibited a record polarization enhancement to 0.52 mA cm-2 at 1.23 VRHE in pH = 11. This work provides a more accurate insight into the pH-dependent effect of ferroelectric polarization on the OER dynamic pathway than conventional models that are based solely on the regulation of band bending.

Self-Supported α-MoB/β-MoB2 Ceramic Electrodes for Efficient High-Current-Density Hydrogen Evolution in Acidic, Neutral, and Alkaline pH-Values

This paper describes the production and high-current-density hydrogen evolution reaction (HER) performance in the whole pH range (from acidic to basic pH values) of self-supported α-MoB/β-MoB2 ceramic electrodes, aiming for use in industrial electrocatalytic water splitting. Tape-casting and phase-inversion process, followed by sintering, were employed to synthesize self-supported β-MoB2 ceramic electrodes, which exhibited well arranged large finger-like pores, providing numerous active sites and channels for electrolyte entry and hydrogen release. The reaction between β-MoB2 and the sintering aid of MoO3 in situ produces α-MoB/β-MoB2 heterojunctions, which significantly improve the electrocatalytic performance. At a current density of 1000 mA·cm-2, the ceramic electrode manifested an overpotential of 289 mV and 294 mV in acidic and alkaline aqueous solutions, respectively, and a stable operation over time (>100 h). The electrode also performed well in a neutral solution, with an overpotential of 354 mV at 100 mA·cm-2. Theoretical (DFT) calculations demonstrated that the α-MoB/β-MoB2 heterojunction alters the electronic configuration of β-MoB2, favoring an effective electron transfer mechanism; thereby, the adsorption free energy of hydrogen ions is close to zero, and the adsorption and dissociation of water molecules under alkaline and neutral conditions are significantly enhanced.

Defect Engineering of Metal-Based Atomically Thin Materials for Catalyzing Small-Molecule Conversion Reactions

Recently, metal-based atomically thin materials (M-ATMs) have experienced rapid development due to their large specific surface areas, abundant electrochemically accessible sites, attractive surface chemistry, and strong in-plane chemical bonds. These characteristics make them highly desirable for energy-related conversion reactions. However, the insufficient active sites and slow reaction kinetics leading to unsatisfactory electrocatalytic performance limited their commercial application. To address these issues, defect engineering of M-ATMs has emerged to increase the active sites, modify the electronic structure, and enhance the catalytic reactivity and stability. This review provides a comprehensive summary of defect engineering strategies for M-ATM nanostructures, including vacancy creation, heteroatom doping, amorphous phase/grain boundary generation, and heterointerface construction. Introducing recent advancements in the application of M-ATMs in electrochemical small molecule conversion reactions (e.g., hydrogen, oxygen, carbon dioxide, nitrogen, and sulfur), which can contribute to a circular economy by recycling molecules like H2, O2, CO2, N2, and S. Furthermore, a crucial link between the reconstruction of atomic-level structure and catalytic activity via analyzing the dynamic evolution of M-ATMs during the reaction process is established. The review also outlines the challenges and prospects associated with M-ATM-based catalysts to inspire further research efforts in developing high-performance M-ATMs.

High-Entropy Oxychalcogenide for Hydrogen Spillover Enhanced Hydrogen Evolution Reaction in Proton and Anion Exchange Membrane Water Electrolyzers

The hydrogen spillover phenomenon provides an expeditious reaction pathway via hydrogen transfer from a strong H adsorption site to a weak H adsorption site, enabling a cost-efficient hydrogen evolution reaction (HER) analogous to platinum with moderate H adsorption energy. Here, a high-entropy oxychalcogenide (HEOC) comprising Co, Ni, Mo, W, O, Se, and Te is prepared by a two-step electrochemical deposition for hydrogen spillover-enhanced HER in acidic and alkaline water electrolysis. The anodic-cathodic reversal current enables the co-deposition of cations and aliovalent anions, facilitating a glass structure with multiple active sites for hydrogen spillover. The HEOC exhibits low overpotentials of 52 and 57 mV to obtain a current density of 10 mA cm-2 in acidic and alkaline media, respectively, and long-term stability for 500 h. The electrochemical and analytical approaches elucidate the hydrogen transfer toward Mo/W-O sites in both acid and alkaline HERs. Meanwhile, the other sites act as hydrogen adsorption or water dissociation-derived hydroxide adsorption sites, showing accommodable behavior in acidic and alkaline media. The HEOC exhibits a practically high current of 1 A cm-2 at cell voltages of 1.78 and 1.89 V and long-term stability for 100 h in proton and anion exchange membrane water electrolyzers, respectively.

Transforming Adsorbate Surface Dynamics in Aqueous Electrocatalysis: Pathways to Unconstrained Performance

Developing highly efficient catalysts to accelerate sluggish electrode reactions is critical for the deployment of sustainable aqueous electrochemical technologies, yet remains a great challenge. Rationally integrating functional components to tailor surface adsorption behaviors and adsorbate dynamics would divert reaction pathways and alleviate energy barriers, eliminating conventional thermodynamic constraints and ultimately optimizing energy flow within electrochemical systems. This approach has, therefore, garnered significant interest, presenting substantial potential for developing highly efficient catalysts that simultaneously enhance activity, selectivity, and stability. The immense promise and rapid evolution of this design strategy, however, do not overshadow the substantial challenges and ambiguities that persist, impeding the realization of significant breakthroughs in electrocatalyst development. This review explores the latest insights into the principles guiding the design of catalytic surfaces that enable favorable adsorbate dynamics within the contexts of hydrogen and oxygen electrochemistry. Innovative approaches for tailoring adsorbate-surface interactions are discussed, delving into underlying principles that govern these dynamics. Additionally, perspectives on the prevailing challenges are presented and future research directions are proposed. By evaluating the core principles and identifying critical research gaps, this review seeks to inspire rational electrocatalyst design, the discovery of novel reaction mechanisms and concepts, and ultimately, advance the large-scale implementation of electroconversion technologies.

Reversible Hydrogen Acceptor-Donor Enables Relay Mechanism for Nitrate-to-Ammonia Electrocatalysis

Electrocatalytic nitrate reduction is a crucial process for sustainable ammonia production. However, to maximize ammonia yield efficiency, this technology inevitably operates at the potentials more negative than 0 V vs. RHE, leading to high energy consumption and competitive hydrogen evolution. To eradicate this issue, hydrogen tungsten bronze (HxWO3) as reversible hydrogen donor-acceptor is partnered with copper (Cu) to enable a relay mechanism at potentials positive than 0 V vs. RHE, which involves rapid intercalation of H into HxWO3 lattice, prompt de-intercalation of the lattice H and transfer onto Cu, and spontaneous H-mediated nitrate-to-ammonia conversion on Cu. The resulting catalysts demonstrated a high ammonia yield rate of 3332.9±34.1 mmol gcat -1 h-1 and a Faraday efficiency of ~100 % at 0.10 V vs. RHE, displaying a record-low estimated energy consumption of 17.6 kWh kgammonia -1. Using these catalysts, we achieve continuous ammonia production in an enlarged flow cell at a real energy consumption of 17.0 kWh kgammonia -1.

Constructing Unsaturated Ru Atom Arrays Confined in Mn Oxides to Boost Neutral Water Reduction

Recently, Ru single atoms supported on carbon nanomaterials have demonstrated ultrahigh activity for acid hydrogen evolution reaction (HER), however their neutral HER activity remains low due to the sluggish kinetics for both the water dissociation step to generate H* intermediates and subsequent H* recombination in neutral electrolytes. Here, we synthesize ordered low-coordinated Ru atom arrays confined in Mn oxides (i.e., Li4Mn5O12) for concurrently boosting the water dissociation and H* recombination, thus achieving a 6-fold HER activity enhancement than commercial Pt/C in neutral media. Control experiments indicate that low-coordinated Ru atoms with strong affinity to oxygen atoms of water molecules facilitate the water dissociation to rapidly generate H*. More importantly, both electrochemical and theoretic results uncover that the array-like structure allows the activation of two water molecules on two adjacent Ru atoms for enabling direct H*-H* recombination via the Tafel step, while isolated Ru atoms can only activate water one by one for recombining H* via the sluggish Heyrovsky step. Clearly, this work paves new avenues to boosting the electrocatalytic activity by constructing ordered metal atoms assembles with controllable coordination environments.

Termination-acidity tailoring of molybdenum carbides for alkaline hydrogen evolution reaction

Transition-metal carbides have been advocated as the promising alternatives to noble-metal platinum-based catalysts in electrocatalytic hydrogen evolution reaction over half a century. However, the effectiveness of transition-metal carbides catalyzing hydrogen evolution in high-pH electrolyte is severely compromised due to the lowered proton activity and intractable alkaline-leaching issue of transition-metal centers. Herein, on the basis of validation of molybdenum-carbide model-catalyst system by taking advantage of surface science techniques, Mo2C micro-size spheres terminated by Al3+ doped MoO2 layer exhibit a notable performance of alkaline hydrogen evolution with a near-zero onset-potential, a low overpotential (40 mV) at a typical current density of 10 mA/cm2, and a small Tafel slope (45 mV/dec), as well as a long-term stability for continuous hydrogen production over 200 h. Advanced morphology and spectroscopy characterizations demonstrate that the local -Al-OH-Mo- structures within Al-MoO2 terminations serve as strong Brønsted acid sites that accelerate the deprotonation kinetics in alkaline HER process. Our work paves an interesting termination-acidity-tailoring strategy to explore cost-effective catalysts towards water electrolysis and beyond.

Amorphous/Crystalline ZrO2 with Oxygen Vacancies Anchored Nano-Ru Enhance Reverse Hydrogen Spillover in Alkaline Hydrogen Evolution

Hydrogen spillover-based binary (HSBB) system has attracted significant attention in alkaline hydrogen evolution reaction (HER). Accelerating hydrogen spillover in the HSBB system is crucial for the HER activity. Herein, a highly efficient HSBB system is developed by anchoring nano-Ru on oxygen vacancy (Vo) rich amorphous/crystal ZrO2. Theoretical and experimental results reveal that the water molecules dissociate on the Vo of ZrO2 into protons, which then couple with electrons to form H*, and the produced H* are spilled over to the nano-Ru to evolve H2. The amorphous regions enhance the adsorption and desorption rates of hydrogen while exposing a greater number of active sites; meanwhile, the Vo significantly reduce the work function of ZrO2, facilitates electron transfer from ZrO2 to Ru, and thereby accelerates hydrogen spillover. As a result, the Ru/ac-ZrO2 delivers a low overpotential of 14 mV at 10 mA cm-2 and a high mass activity of 46.47 A mgmetal -2 at 300 mV for alkaline HER, bypass those of commercial Pt/C (19 mV and 0.09 A mgmetal -2, respectively).

Electronic Metal-Support Interaction Induces Hydrogen Spillover and Platinum Utilization in Hydrogen Evolution Reaction

The substantial promotion of hydrogen evolution reaction (HER) catalytic performance relies on the breakup of the Sabatier principle, which can be achieved by the alternation of the support and electronic metal support interaction (EMSI) is noticed. Due to the utilization of tungsten disulfides as support for platinum (Pt@WS2), surprisingly, Pt@WS2 demands only 31 mV overpotential to attain 10 mA cm-2 in acidic HER test, corresponding to a 2.5-fold higher mass activity than benchmarked Pt/C. The pH dependent electrochemical measurements associated with H2-TPD and in situ Raman spectroscopy indicate a hydrogen spillover involved HER mechanism is confirmed. The WS2 support triggers a higher hydrogen binding strength for Pt leading to the increment in hydrogen concentration at Pt sites proved by upshifted d band center as well as lower Gibbs free energy of hydrogen, favourable for hydrogen spillover. Besides, the WS2 shows a comparably lower effect on Gibbs free energy for different Pt layers (-0.50 eV layer-1) than carbon black (-0.88 eV layer-1) contributing to a better Pt utilization. Also, the theoretical calculation suggests the hydrogen spillover occurs on the 3rd Pt layer in Pt@WS2; moreover, the energy barrier is lowered with increment in hydrogen coverage on Pt. Therefore, the boosted HER activity attributes to the EMSI effect caused hydrogen spillover and enhancement in Pt utilization efficiency.

Achieving Excess Hydrogen Output via Concurrent Electrochemical and Chemical Redox Reactions on P-Doped Co-Based Catalysts with Electron Manipulation and Kinetic Regulation

Electrolytic hydrogen production is of great significance in energy conversion and sustainable development. Traditional electrolytic water splitting confronts high anode voltage with oxygen generation and the amount of hydrogen produced at cathode depends entirely on the quantity of electric charge input. Herein, excess hydrogen output can be achieved by constructing a spontaneous hydrazine oxidation reaction (HzOR) coupled hydrogen evolution reaction (HER) system. For the hydrazine oxidation-assisted electrolyzer in this work, both the external input electrons and the electrons produced by spontaneous chemical redox reaction can reduce water, producing more hydrogen than traditional electrolytic water splitting system. The ultrafast kinetics of bifunctional P-doped Co-based catalysts plays a key role in the spontaneous feature of HzOR/HER redox reaction and low working voltage of hydrazine oxidation-assisted electrolyzer (12 mV@100 mA cm-2). Theoretical calculation results and ex situ/in situ spectra demonstrate that doped P could optimize electronic structure, regulate adsorption energy of intermediates, and thus endows catalysts with ultrafast kinetics. This work provides a new pathway for the development of spontaneous oxidation-assisted hydrogen production, to achieve excess hydrogen output via concurrent electrochemical and chemical redox reactions.

NADPH Oxidases-Inspired Reactive Oxygen Biocatalysts with Electron-Rich Pt Sites to Potently Amplify Immune Checkpoint Blockade Therapy

Clinical immune checkpoint blockade (ICB)-based immunotherapy of malignant tumors only elicits durable responses in a minority of patients, primarily due to the highly immunosuppressive tumor microenvironment. Although inducing immunogenic cell death (ICD) through reactive oxygen biocatalyst represents an attractive therapeutic strategy to amplify ICB, currently reported biocatalysts encounter insurmountable challenges in achieving high ROS-generating activity to induce potent ICD. Here, inspired by the natural catalytic characteristics of NADPH oxidases, the design of efficient, robust, and electron-rich Pt-based redox centers on the non-stoichiometric W18O49 substrates (Pt─WOx) to serve as bioinspired reactive oxygen biocatalysts to potently activate the ICD, which eventually enhance cancer immune responses and amplifies the ICB-based immunotherapy is reported. These studies demonstrate that the Pt─WOx exhibits rapid electron transfer capability and can promote the formation of electron-rich and low oxophilic Pt redox centers for superior reactive oxygen biocatalysis, which enables the Pt─WOx-based inducers to trigger endoplasmic reticulum stress directly and stimulate immune responses potently for amplifying the anti-PD-L1-based ICB therapy. This bioinspired design provides a straightforward strategy to engineer efficient, robust, and electron-rich reactive oxygen biocatalysts and also opens up a new avenue to create efficient ICD inducers for primary/metastatic tumor treatments.

Ultrafast H-Spillover in Intermetallic PtZn Induced by the Local Disorder for Excellent Electrocatalytic Hydrogen Evolution Performance

Ordered intermetallic Platinum-Zinc (PtZn) shows potential in hydrogen evolution reaction (HER), but faces a huge challenge in activity enhancement due to the H-repulsion properties of Zinc (Zn). Here, local disorder in ordered intermetallic PtZn nanoparticles confined in N-doped porous carbon (I-PtZn@NPC) via a confinement-high-temperature pyrolysis strategy is realized to boost the HER performance. Experiments and calculations demonstrate that the local substitution of Pt atoms for Zn atoms creates an ultra-short H-spillover channel (Pt site→Pt-Zn bridge site →Zn site). Benefiting from such an ultra-fast H-migration from Pt site to Zn site, I-PtZn@NPC exhibits enhanced intrinsic activity with an ultralow overpotential (η10: 2.3 mV, η100: 24 mV) than commercial Pt black catalyst. Furthermore, a 25 cm2 commercial proton exchange membrane (PEM) electrolyzer equipped with I-PtZn@NPC achieved stable operation at 1.60 Vcell for 200 h at a current density of 1 A cm⁻2. This design of local Zn disorder in the ordered intermetallic PtZn sheds new light on the rational development of efficient Zn-based alloy HER electrocatalysts.

Hydrogen Spillover-Bridged Interfacial Water Activation of WCx and Hydrogen Recombination of Ru as Dual Active Sites for Accelerating Electrocatalytic Hydrogen Evolution

Tungsten carbide (WCx) is a promising alternative to platinum catalysts for hydrogen evolution reaction (HER). However, strong tungsten-hydrogen bond hinders hydrogen desorption while favoring H+ reduction, thus limiting HER kinetics. Inspired by the phenomenon of hydrogen spillover in heterogeneous catalysis, a ruthenium (Ru) doped-driven activated hydrogen migration from WCx surface to Ru is reported. This approach achieved high activity with an ultralow overpotential of 9.0 mV at 10 mA·cm-2 and superior stability at an industrial-grade current density of 1.0 A·cm-2 @ 1.65 V. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and operando electrochemical impedance spectra revealed that this exceptional hydrogen production-which surpasses that of previously reported Pt/C catalysts-is attributable to the outstanding ability of WCx to induce water dissociation and hydrogen spillover from WCx to Ru surface. During the HER process, the rigid interfacial water network negatively affected the HER efficiency under alkaline conditions. The WCx sites disrupted this rigid structure, facilitating the contact between activated hydrogen (H*) and WCx sites. Subsequently, H* migrates to Ru surface, where hydrogen recombination occurs to produce H2. This work paves a new avenue for the construction of coupled catalysts at the atomic scale to facilitate HER electrocatalysis.

Dynamic Creation of a Local Acid-like Environment for Hydrogen Evolution Reaction in Natural Seawater

Electrolysis of natural seawater driven by renewable energy is practically attractive for green hydrogen production. However, because precipitation initiated by an increase in local pH near to the cathode deactivates catalysts or blocks electrolyzer channels, limited catalysts are capable of operating with untreated, natural seawater (viz., pH 8.2 to 8.3 and ca. 35 g salts L-1); most are used in strongly alkaline or acidic seawater. Here, we report a new natural seawater electrolysis cathode with precipitation-suppression via a Pt/WO2 catalyst to create a dynamically local acid-like environment. The in situ formed hydrogen tungsten bronze (HxWOy) phase via continuous hydrogen insertion from water acts as a proton reservoir. As a result, dynamically stored protons create a local acid-like environment near the Pt active sites. We evidence that this tailored acid-like environment boosts the hydrogen evolution reaction in natural seawater splitting and neutralizes generated OH- species to restrict precipitation formations. Consequently, a long-term stability of >500 h at 100 mA cm-2 was exhibited in direct seawater electrolysis.

Operando Stable Palladium Hydride Nanoclusters Anchored on Tungsten Carbides Mediate Reverse Hydrogen Spillover for Hydrogen Evolution

Proton exchange membrane (PEM) electrolysis holds great promise for green hydrogen production, but suffering from high loading of platinum-group metals (PGM) for large-scale deployment. Anchoring PGM-based materials on supports can not only improve the atomic utilization of active sites but also enhance the intrinsic activity. However, in practical PEM electrolysis, it is still challenging to mediate hydrogen adsorption/desorption pathways with high coverage of hydrogen intermediates over catalyst surface. Here, operando generated stable palladium (Pd) hydride nanoclusters anchored on tungsten carbide (WCx) supports were constructed for hydrogen evolution in PEM electrolysis. Under PEM operando conditions, hydrogen intercalation induces formation of Pd hydrides (PdHx) featuring weakened hydrogen binding energy (HBE), thus triggering reverse hydrogen spillover from WCx (strong HBE) supports to PdHx sites, which have been evidenced by operando characterizations, electrochemical results and theoretical studies. This PdHx-WCx material can be directly utilized as cathode electrocatalysts in PEM electrolysis with ultralow Pd loading of 0.022 mg cm-2, delivering the current density of 1 A cm-2 at the cell voltage of ~1.66 V and continuously running for 200 hours without obvious degradation. This innovative strategy via tuning the operando characteristics to mediate reverse hydrogen spillover provide new insights for designing high-performance supported PGM-based electrocatalysts.

Synergistic effects of interface and phase engineering on telluride toward alkaline/neutral hydrogen evolution reaction in freshwater/seawater

The development of efficient, stable, and versatile hydrogen evolution electrocatalysts is of great meaning, but still faces challenging. Interface engineering and phase engineering have been immensely applied in the field of hydrogen evolution reaction (HER) because of their unique physicochemical properties. However, they are typically used separately, which limits their effectiveness. Herein, we propose an interface-engineered CoMo/CoTe electrocatalyst, consisting of an amorphous CoMo (a-CoMo) layer-encapsulated crystalline CoTe array, achieving the profound optimization of catalytic performance. The experimental results and density functional theory calculations show that the d-band center of the catalyst shifts further upward in contrast with its crystalline-crystalline counterpart, optimizing the electronic structure and the intermediate adsorption, thereby reducing the kinetic barrier of HER. The a-CoMo/CoTe with superhydrophilic/superaerophobic features shows excellent catalytic performance in alkaline, neutral, and simulated seawater environments.

A hierarchical WC/NiCoW hollow nanotube array as a highly efficient electrocatalyst for hydrogen evolution

The hydrogen evolution reaction (HER) holds great potential for sustainable hydrogen production but developing efficient and cost-effective electrocatalysts remains challenging. Here, we report the synthesis of a hierarchical WC/NiCoW hollow nanotube array electrocatalyst, featuring rapid gas release to minimize bubble aggregation and reaction retardation. Mechanistic insights into the HER kinetics reveal enhanced electron transfer at the WC-NiCoW interface and an accelerated Volmer step. The optimized WC/NCW-600 exhibits superior HER activity and remarkable long-term stability for over 72 h in alternated acidic, neutral, and alkaline electrolytes. This work highlights new insights into the rational structural design of durable electrocatalysts for hydrogen production.

Ampere-Level Hydrogen Generation via 1000 H Stable Seawater Electrolysis Catalyzed by Pt-Cluster-Loaded NiFeCo Phosphide

Seawater electrolysis can generate carbon-neutral hydrogen but its efficiency is hindered by the low mass activity and poor stability of commercial catalysts at industrial current densities. Herein, Pt nanoclusters are loaded on nickel-iron-cobalt phosphide nanosheets, with the obtained Pt@NiFeCo-P electrocatalyst exhibiting excellent hydrogen evolution reaction (HER) activity and stability in alkaline seawater at ampere-level current densities. The catalyst delivers an ultralow HER overpotential of 19.7 mV at -10 mA cm-2 in seawater-simulating alkaline solutions, along with a Pt-mass activity 20.8 times higher than Pt/C under the same conditions, while dropping to 8.3 mV upon a five-fold NaCl concentrated natural seawater. Remarkably, Pt@NiFeCo-P offers stable operation for over 1000 h at 1 A cm-2 in an alkaline brine electrolyte, demonstrating its potential for efficient and long-term seawater electrolysis. X-ray photoelectron spectroscopy (XPS), in situ electrochemical impedance spectroscopy (EIS), and in situ Raman studies revealed fast electron and charge transfer from the NiFeCo-P substrate to Pt nanoclusters enabled by a strong metal-support interaction, which increased the coverage of H* and accelerated water dissociation on high valent Co sites. This study represents a significant advancement in the development of efficient and stable electrocatalysts with high mass activity for sustainable hydrogen generation from seawater.

Material Engineering Strategies for Efficient Hydrogen Evolution Reaction Catalysts

Water electrolysis, a key enabler of hydrogen energy production, presents significant potential as a strategy for achieving net-zero emissions. However, the widespread deployment of water electrolysis is currently limited by the high-cost and scarce noble metal electrocatalysts in hydrogen evolution reaction (HER). Given this challenge, design and synthesis of cost-effective and high-performance alternative catalysts have become a research focus, which necessitates insightful understandings of HER fundamentals and material engineering strategies. Distinct from typical reviews that concentrate only on the summary of recent catalyst materials, this review article shifts focus to material engineering strategies for developing efficient HER catalysts. In-depth analysis of key material design approaches for HER catalysts, such as doping, vacancy defect creation, phase engineering, and metal-support engineering, are illustrated along with typical research cases. A special emphasis is placed on designing noble metal-free catalysts with a brief discussion on recent advancements in electrocatalytic water-splitting technology. The article also delves into important descriptors, reliable evaluation parameters and characterization techniques, aiming to link the fundamental mechanisms of HER with its catalytic performance. In conclusion, it explores future trends in HER catalysts by integrating theoretical, experimental and industrial perspectives, while acknowledging the challenges that remain.

Phase Engineering-Mediated D-Band Center of Ru Sites Promote the Hydrogen Evolution Reaction Under Universal pH Condition

The rational design of pH-universal electrocatalyst with high-efficiency, low-cost and large current output suitable for industrial hydrogen evolution reaction (HER) is crucial for hydrogen production via water splitting. Herein, phase engineering of ruthenium (Ru) electrocatalyst comprised of metastable unconventional face-centered cubic (fcc) and conventional hexagonal close-packed (hcp) crystalline phase supported on nitrogen-doped carbon matrix (fcc/hcp-Ru/NC) is successfully synthesized through a facile pyrolysis approach. Fascinatingly, the fcc/hcp-Ru/NC displayed excellent electrocatalytic HER performance under a universal pH range. To deliver a current density of 10 mA cm-2, the fcc/hcp-Ru/NC required overpotentials of 16.8, 23.8 and 22.3 mV in 1 M KOH, 0.5 M H2SO4 and 1 M phosphate buffered solution (PBS), respectively. Even to drive an industrial-level current density of 500 and 1000 mA cm-2, the corresponding overpotentials are 189.8 and 284 mV in alkaline, 202 and 287 mV in acidic media, respectively. Experimental and theoretical calculation result unveiled that the charge migration from fcc-Ru to hcp-Ru induced by work function discrepancy within fcc/hcp-Ru/NC regulate the d-band center of Ru sites, which facilitated the water adsorption and dissociation, thus boosting the electrocatalytic HER performance. The present work paves the way for construction of novel and efficient electrocatalysts for energy conversion and storage.

Independent Control Over the H/OH Adsorption: Breaking the Trade-Off Between H/OH-Adsorption and H2O-Dissociation of Platinum-Group Metal Electrocatalyst for Hydrogen Evolution Reaction

Platinum-group metals catalysts (such as Rh, Pd, Ir, Pt) have been the most efficient hydrogen evolution reaction (HER) electrocatalysts due to their moderate H adsorption strength, while the high H2O-dissociation barrier in alkaline media restrains the catalytic performance of PGM catalysts. However, the optimization of the H2O-dissociation barrier and *H/*OH binding energy toward their individual optima is limited due to the constraints of their scaling relationship on a single active site. Here, a coordinatively unsaturated "M─Ox─W" (M = Rh, Pd, Ir, Pt) active area is constructed, where H and OH species are anchored on Pt-group metal sites and inactive W sites for individual regulation. By combining experiments and density functional theory calculations, the introduction of extra OH-adsorption sites (coordinatively unsaturated WO3-x) avoids the competitive adsorption of H and OH on the single site, while the enhanced OH-adsorption capacity on the coordinatively unsaturated WO3-x effectively facilitates the adsorption/dissociation of interfacial H2O. As a result, the representative Rh-WO3-x catalyst exhibits outstanding catalytic activity and durability for HER. The findings of this work not only provide valuable insights for the design of efficient PGM catalysts for HER but also shed light on the development of electrocatalysts for other catalytic reactions.

Proton Ionic Liquid Modulates Hydrogen Coverage and Subsurface Absorbed Hydrogen to Enhance Pd Metallene Electrocatalytic Semi-hydrogenation of Alkynols

Electrochemical semi-hydrogenation of alkynols to produce high-value alkenols is a green and sustainable approach. Although Pd can exhibit excellent semi-hydrogenation properties, its intrinsic mechanism still lacks in-depth study. Herein, a proton ionic liquid (PIL)-modified Pd metallene (Pdene@PIL) is synthesized for the electrocatalytic semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE). The PIL modification of Pdene@PIL resulted in an MBY conversion of 96.1% and MBE selectivity of 97.2%, respectively. Theoretical calculations indicate the electron transfer between Pdene and PIL, leading to easier adsorption of MBY on the Pd surface. The d-band center of Pdene@PIL shifts away from the Fermi level, which weakens the adsorption of over-hydrogenated intermediates. At the same time, the PIL modification facilitates the adsorption of surface-adsorbed hydrogen (H*ads) and inhibits the formation of subsurface-absorbed hydrogen (H*abs). In particular, the PIL modification optimizes Hads* coverage, reduces the reaction energy of the rate-determining step (C5H8O*-C5H9O*), and inhibits HER. The reduction of H*abs formation inhibits the transfer of Pd to PdHx and suppresses the over-hydrogenation. This work provides new insights into the modulation of H* to enhance the alkynol electrocatalytic semi-hydrogenation reaction (ESHR) process from the perspective of surface modification.