Ultralow Ru Incorporated Amorphous Cobalt-Based Oxides for High-Current-Density Overall Water Splitting in Alkaline and Seawater Media

Ru nanocrystals modified porous FeOOH nanostructures with open 3D interconnected architecture supported on NiFe foam as high-performance electrocatalyst for oxygen evolution reaction and electrocatalytic urea oxidation

The construction of binder-free electrodes with well-defined three-dimensional (3D) morphology and optimized electronic structure represents an efficient strategy for the design of high-performance electrocatalysts for the development of efficient green hydrogen technologies. Herein, Ru nanocrystals were modified on 3D interconnected porous FeOOH nanostructures with open network-like frameworks on NiFe foam (Ru/FeOOH@NFF), which were used as an efficient electrocatalyst. In this study, a 3D interconnected porous FeOOH with an open network structure was first electrodeposited on NiFe foam and served as the support for the in-situ modification of Ru nanocrystals. Subsequently, the Ru nanocrystals and abundant oxygen vacancies were simultaneously incorporated into the FeOOH matrix via the adsorption-reduction method, which involved NaBH4 reduction. The Ru/FeOOH@NFF electrocatalyst shows a large specific surface area, abundant oxygen vacancies, and modulated electronic structure, which collectively result in a significant enhancement of catalytic properties with respect to the oxygen evolution reaction (OER) and urea oxidation reaction (UOR). The Ru/FeOOH@NFF catalyst exhibits an outstanding OER performance, requiring a low overpotential (360 mV) at 200 mA cm-2 with a small Tafel slope (58 mV dec-1). Meanwhile, the Ru/FeOOH@NFF catalyst demonstrates more efficient UOR activity for achieving 200 mA cm-2 at a lower overpotential of 272 mV. Furthermore, an overall urea electrolysis cell using the Ru/FeOOH@NFF as the anode and Pt as the cathode (Ru/FeOOH@NFF||Pt) reveals a cell voltage of 1.478 V at 10 mA cm-2 and a prominent durability (120 h at 50 mA cm-2). This work will provide a valuable understanding of the construction of high-performance electrocatalysts with 3D microstructure for promoting urea-assisted water electrolysis.

Electronic redistribution induced by interaction between ruthenium nanoparticles and Ni-N(O)-C sites boosts alkaline water electrolysis

Ultrafine ruthenium nanoparticles are encapsulated by single-atom Ni-bonded graphitic carbon nitride (g-C3N4) layers anchored on carbon nanotubes (Ru/Ni-CNCT). The enhanced electronic interaction between Ru nanoparticles and Ni-N(O)-C sites anchored in g-C3N4 layers promotes water adsorption/dissociation and hydrogen evolution.

Ru Single-Atom Nanoarchitectonics on Co-Based Conducting Metal-Organic Frameworks for Enhanced Oxygen Evolution Reaction

The development of oxygen evolution reaction (OER) electrocatalysts is essential for the production of green hydrogen from water electrolysis, but it is challenging. Herein, ruthenium (Ru) single-atom-modified Co-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) (Ru@Co-HHTP) was prepared via a solvothermal and ion exchange method. Systematic experiments highlight that the atomically dispersed Ru can optimize the electronic structure and electronic conductivity of Co-HHTP. As a result, the obtained Ru@Co-HHTP shows a low overpotential of 247 mV at 100 mA cm-2, a small Tafel slope of 38.14 mV dec-1, and good stability, which are superior to those of Co-HHTP, commercial IrO2, and most previously reported catalysts. This work provides a new avenue for designing highly efficient elongated OER electrocatalysts.

Bifunctional Amorphous Transition-Metal Phospho-Boride Electrocatalysts for Selective Alkaline Seawater Splitting at a Current Density of 2A cm-2

Hydrogen production by direct seawater electrolysis is an alternative technology to conventional freshwater electrolysis, mainly owing to the vast abundance of seawater reserves on earth. However, the lack of robust, active, and selective electrocatalysts that can withstand the harsh and corrosive saline conditions of seawater greatly hinders its industrial viability. Herein, a series of amorphous transition-metal phospho-borides, namely Co-P-B, Ni-P-B, and Fe-P-B are prepared by simple chemical reduction method and screened for overall alkaline seawater electrolysis. Co-P-B is found to be the best of the lot, requiring low overpotentials of ≈270 mV for hydrogen evolution reaction (HER), ≈410 mV for oxygen evolution reaction (OER), and an overall voltage of 2.50 V to reach a current density of 2 A cm-2 in highly alkaline natural seawater. Furthermore, the optimized electrocatalyst shows formidable stability after 10,000 cycles and 30 h of chronoamperometric measurements in alkaline natural seawater without any chlorine evolution, even at higher current densities. A detailed understanding of not only HER and OER but also chlorine evolution reaction (ClER) on the Co-P-B surface is obtained by computational analysis, which also sheds light on the selectivity and stability of the catalyst at high current densities.

Unveiling the potential of amorphous nanocatalysts in membrane-based hydrogen production

Hydrogen, as a clean and renewable energy source, is a promising candidate to replace fossil fuels and alleviate the environmental crisis. Compared with the traditional H-type cells with a finite-gap, the design of membrane electrodes can reduce the gas transmission resistance, enhance the current density, and improve the efficiency of hydrogen production. However, the harsh environment in the electrolyser makes the membrane electrode based water electrolysis technology still limited by the lack of catalyst activity and stability under the working conditions. Due to the abundant active sites and structural flexibility, amorphous nanocatalysts are alternatives. In this paper, we review the recent research progress of amorphous nanomaterials as electrocatalysts for hydrogen production by electrolysis at membrane electrodes, illustrate and discuss their structural advantages in membrane electrode catalytic systems, as well as explore the significance of the amorphous structure for the development of membrane electrode systems. Finally, the article also looks at future opportunities and adaptations of amorphous catalysts for hydrogen production at membrane electrodes. The authors hope that this review will deepen the understanding of the potential of amorphous nanomaterials for application in electrochemical hydrogen production, facilitating future nanomaterials research and new sustainable pathways for hydrogen production.

Electron Redistribution of Ru Site on MoO2@NiMoO4 Support for Efficient Ampere-Level Current Density Electrolysis of Alkaline Seawater

Seawater electrolysis is a promising but challenging strategy to generate carbon-neutral hydrogen. A grand challenge for hydrogen evolution reaction (HER) from alkaline seawater electrolysis is the development of efficient and stable electrocatalysts to overcome the limitation of sluggish kinetics. Here, a 3D nanorod hybrid catalyst is reported, which comprises heterostructure MoO2@NiMoO4 supported Ru nanoparticles (Ru/ MoO2@NiMoO4) with a size of ≈5 nm. Benefitting from the effect of strongly coupled interaction, Ru/MoO2@NiMoO4 catalyst exhibits a remarkable alkaline seawater hydrogen evolution performance, featured by a low overpotential of 184 mV at a current density of 1.0 A cm-2, superior to commercial Pt/C (338 mV). Experimental observations demonstrate that the heterostructure MoO2@NiMoO4 as an electron-accepting support makes the electron transfer from the Ru nanoparticles to MoO2, and thereby implements the electron redistribution of Ru site. Mechanistic analysis elucidates that the electron redistribution of active Ru site enhances the ability of hydrogen desorption, thereby promoting alkaline seawater HER kinetics and finally leading to a satisfactory catalysis performance at ampere-level current density of alkaline seawater electrolysis.

Ruthenium-Based Electrocatalysts for Hydrogen Evolution Reaction: from Nanoparticles to Single Atoms

Benefiting from similar hydrogen bonding energy to Pt and much lower price compare with Pt, Ru based catalysts are promising candidates for electrocatalytic hydrogen evolution reaction (HER). The catalytic activity of Ru nanoparticles can be enhanced through improving their dispersion by using different supports, and the strong metal supports interaction can further regulate their catalytic performance. In addition, single-atom catalysts (SACs) with almost 100% atomic utilization attract great attention and the coordinative atmosphere of single atoms can be adjusted by supports. Moreover, the syngenetic effects of nanoparticles and single atoms can further improve the catalytic performance of Ru based catalysts. In this review, the progress of Ru based HER electrocatalysts are summarized according to their existing forms, including nanoparticles (NPs), single atoms (SAs) and the combination of both NPs and SAs. The common supports such as carbon materials, metal oxides, metal phosphides and metal sulfides are classified to clarify the metal supports interaction and coordinative atmosphere of Ru active centers. Especially, the possible catalytic mechanisms and the reasons for the improved catalytic performance are discussed from both experimental results and theoretical calculations. Finally, some challenges and opportunities are prospected to facilitate the development of Ru based catalysts for HER.

Design Strategies of Hydrogen Evolution Reaction Nano Electrocatalysts for High Current Density Water Splitting

Hydrogen is now recognized as the primary alternative to fossil fuels due to its renewable, safe, high-energy density and environmentally friendly properties. Efficient hydrogen production through water splitting has laid the foundation for sustainable energy technologies. However, when hydrogen production is scaled up to industrial levels, operating at high current densities introduces unique challenges. It is necessary to design advanced electrocatalysts for hydrogen evolution reactions (HERs) under high current densities. This review will briefly introduce the challenges posed by high current densities on electrocatalysts, including catalytic activity, mass diffusion, and catalyst stability. In an attempt to address these issues, various electrocatalyst design strategies are summarized in detail. In the end, our insights into future challenges for efficient large-scale industrial hydrogen production from water splitting are presented. This review is expected to guide the rational design of efficient high-current density water electrolysis electrocatalysts and promote the research progress of sustainable energy.

Built-In Electric Field Boosted Overall Water Electrolysis at Large Current Density for the Heterogeneous Ir/CoMoO4 Nanosheet Arrays

Advanced bifunctional electrocatalysts are essential for propelling overall water splitting (OWS) progress. Herein, relying on the obvious difference in the work function of Ir (5.44 eV) and CoMoO4 (4.03 eV) and the constructed built-in electric field (BEF), an Ir/CoMoO4/NF heterogeneous catalyst, with ultrafine Ir nanoclusters (1.8 ± 0.2 nm) embedded in CoMoO4 nanosheet arrays on the surface of nickel foam skeleton, is reported. Impressively, the Ir/CoMoO4/NF shows remarkable electrocatalytic bifunctionality toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), especially at large current densities, requiring only 13 and 166 mV to deliver 10 and 1000 mA cm-2 for HER and 196 and 318 mV for OER. Furthermore, the Ir/CoMoO4/NF||Ir/CoMoO4/NF electrolyzer demands only 1.43 and 1.81 V to drive 10 and 1000 mA cm-2 for OWS. Systematical theoretical calculations and tests show that the formed BEF not only optimizes interfacial charge distribution and the Fermi level of both Ir and CoMoO4, but also reduces the Gibbs free energy (ΔGH*, from 0.25 to 0.03 eV) and activation energy (from 13.6 to 8.9 kJ mol-1) of HER, the energy barrier (from 3.47 to 1.56 eV) and activation energy (from 21.1 to 13.9 kJ mol-1) of OER, thereby contributing to the glorious electrocatalytic bifunctionality.

Platinum-Ruthenium Dual-Atomic Sites Dispersed in Nanoporous Ni0.85Se Enabling Ampere-Level Current Density Hydrogen Production

Alkaline anion-exchange-membrane water electrolyzers (AEMWEs) using earth-abundant catalysts is a promising approach for the generation of green H2. However, the AEMWEs with alkaline electrolytes suffer from poor performance at high current density compared to proton exchange membrane electrolyzers. Here, atomically dispersed Pt-Ru dual sites co-embedded in nanoporous nickel selenides (np/Pt1Ru1-Ni0.85Se) are developed by a rapid melt-quenching approach to achieve highly-efficient alkaline hydrogen evolution reaction. The np/Pt1Ru1-Ni0.85Se catalyst shows ampere-level current density with a low overpotential (46 mV at 10 mA cm-2 and 225 mV at 1000 mA cm-2), low Tafel slope (32.4 mV dec-1), and excellent long-term durability, significantly outperforming the benchmark Pt/C catalyst and other advanced large-current catalysts. The remarkable HER performance of nanoporous Pt1Ru1-Ni0.85Se is attributed to the strong intracrystal electronic metal-support interaction (IEMSI) between Pt-Se-Ru sites and Ni0.85Se support which can greatly enlarge the charge redistribution density, reduce the energy barrier of water dissociation, and optimize the potential determining step. Furthermore, the assembled alkaline AEMWE with an ultralow Pt and Ru loading realizes an industrial-level current density of 1 A cm-2 at 1.84 volts with high durability.

CuOx/Cu nanorod skeleton supported Ru-doped CoO/NC nanocomposites for overall water splitting

High overpotential and low stability are major challenges for hydrogen evolution reaction (HER)/oxygen evolution reaction (OER). Tuning the electronic structure of catalysts is regarded as a core strategy to enhance catalytic activity. Herein, we report CuOx/Cu nanorod skeleton supported Ru doped cobalt oxide/nitrogen-doped carbon nanocomposites (Ru-CoO/NC/CuOx/Cu, denoted as RCUF) as bifunctional catalysis. The one-dimensional/three-dimensional (1D/3D) nanostructure and defect-rich amorphous/crystalline phases of RCUF facilitates active site exposure and electron transport. Experimental characterization and density functional theory (DFT) calculation results indicate that Ru doping can optimize the electronic structure, which accelerates the water dissociation process and reduces the Gibbs free energy of the reaction intermediates. As expected, the optimal RCUF-900 exhibits low overpotential (25/205 mV at 10 mA cm-2) and high stability (100/100 h) for HER/OER. RCUF-900 has low voltage (1.54 V at 10 mA cm-2) and high stability (100 h) for overall water splitting. This work provides new insights into the design of advanced catalysts for overall water splitting.

Durable Ru Nanocrystal with HfO2 Modification for Acidic Overall Water Splitting

Durable and efficient bi-functional catalyst, that is capable of both oxygen evolution reaction and hydrogen evolution reaction under acidic condition, are highly desired for the commercialization of proton exchange membrane water electrolysis. Herein, we report a robust L-Ru/HfO2 heterostructure constructed via confining crystalline Ru nanodomains by HfO2 matrix. When assembled with a proton exchange membrane, the bi-functional L-Ru/HfO2 catalyst-based electrolyzer presents a voltage of 1.57 and 1.67 V to reach 100 and 300 mA cm-2 current density, prevailing most of previously reported Ru-based materials as well as commercial Pt/C||RuO2 electrolyzer. It is revealed that the synergistic effect of HfO2 modification and small crystalline domain formation significantly alleviates the over-oxidation of Ru. More importantly, this synergistic effect facilitates a dual-site oxide path during the oxygen evolution procedure via optimization of the binding configurations of oxygenated adsorbates. As a result, the Ru active sites maintain the metallic state along with reduced energy barrier for the rate-determining step (*O→*OOH). Both of water adsorption and dissociation (Volmer step) are strengthened, while a moderate hydrogen binding is achieved to accelerate the hydrogen desorption procedure (Tafel step). Consequently, the activity and stability of acidic overall water splitting are simultaneously enhanced.

In Situ Electrodeposition of Ultralow Pt into NiFe-Metal-Organic Framework/Nickel Foam Nanosheet Arrays as a Bifunctional Catalyst for Overall Water Splitting

Exploring highly effective bifunctional electrocatalysts with surface structural advantages and synergistic optimization effects among multimetals is greatly important for overall water splitting. Herein, we successfully synthesized Pt-loaded NiFe-metal-organic framework nanosheet arrays grown on nickel foam (Pt-NiFe-MOF/NF) via a facile hydrothermal-electrodeposition process. Benefiting from large exposed specific surface, optimal electrical conductivity and efficient metal-support interaction endow Pt-NiFe-MOF/NF with highly catalytic performance, exhibiting small overpotential of 261 mV toward oxygen evolution reaction and 125 mV toward hydrogen evolution reaction at a current density of 100 mA cm-2 in alkaline medium. More significantly, the assembled water electrolyzer comprising the Pt-NiFe-MOF/NF//Pt-NiFe-MOF/NF couple demands a low cell voltage of 1.45 V to reach 10 mA cm-2. This work renders a viable approach to design dual-functional electrocatalysts with exceptional electrocatalytic activity and stability at high current density, showing the great prospect of water electrolysis for commercial application.

Ru doping induced interface engineering in flower-liked CoMoO4-RuO2 boosts oxygen electrocatalysis for rechargeable Zn-air battery

Constructing heterogeneous catalysts can significantly boost the electrocatalytic activity due to the improved intrinsic catalytic activity induced by tailored electronic structure and optimized chemisorption to the reaction intermediates. RuO2 based electrocatalysts are especially attractive due to the high catalytic activity of RuO2. To reduce the usage of noble metal and improve the catalytic activity of catalyst, CoMoO4-RuO2 micro-flower was synthesized using a facile hydrothermal-calcination method in this work. CoMoO4-RuO2 exhibits a low overpotential of 177 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and a high half-wave potential of 0.858 V for oxygen reduction reaction (ORR). Moreover, the Zn-air battery assembled using CoMoO4-RuO2 exhibit shows a high maximum discharge power density of 149 mW cm-2 and a large open circuit voltage of 1.38 V. The good performance can be attributed to the incorporation of RuO2, which not only induces extra catalytic active sites, but also forms heterojunction with CoMoO4 to optimize the electronic structure of CoMoO4-RuO2, thereby achieving a better equilibrium of absorption and desorption of intermediates. The work provides insights into designing RuO2 based electrocatalysts for advanced electrocatalysis.

Dual-Functional Ru/Ni-B-P Electrocatalyst Toward Accelerated Water Electrolysis and High-Stability

Development of advanced electrocatalysts for the green hydrogen production by water electrolysis is an important task to reduce the climate and environmental issues as well as to meet the future energy demands. Herein, Ru/Ni-B-P sphere electrocatalyst is demonstrated by a combination of hydrothermal and soaking approaches, meeting the industrial requirement of low cell voltage with stable high-current operation. The Ru/Ni-B-P sphere catalyst demonstrates low overpotentials of 191 and 350 mV at 300 mA cm-2 with stable high current operation, ranking it as one of the best oxygen evolution reaction (OER) electrocatalysts. The bifunctional 2-E system demonstrates a low cell voltage of 2.49 V at 2000 mA cm-2 in 6 m KOH at 60 °C of harsh industrial operation condition. It also demonstrates outstanding stability with continuous 120 h (5 days) CA operation at 1000 mA cm-2. Further, the hybrid configuration of Ru/Ni-B-P || Pt/C being paired with the conventional benchmark electrode demonstrates a record low 2-E cell voltage of 2.40 V at 2000 mA cm-2 in 6 m KOH and excellent stability at high current of 1500 mA cm-2 under industrial operational condition.

Spatial configuration of Fe-Co dual-sites boosting catalytic intermediates coupling toward oxygen evolution reaction

Oxygen evolution reaction (OER) is the pivotal obstacle of water splitting for hydrogen production. Dual-sites catalysts (DSCs) are considered exceeding single-site catalysts due to the preternatural synergetic effects of two metals in OER. However, appointing the specific spatial configuration of dual-sites toward more efficient catalysis still remains a challenge. Herein, we constructed two configurations of Fe-Co dual-sites: stereo Fe-Co sites (stereo-Fe-Co DSC) and planar Fe-Co sites (planar-Fe-Co DSC). Remarkably, the planar-Fe-Co DSC has excellent OER performance superior to stereo-Fe-Co DSC. DFT calculations and experiments including isotope differential electrochemical mass spectrometry, in situ infrared spectroscopy, and in situ Raman reveal the *O intermediates can be directly coupled to form *O-O* rather than *OOH by both the DSCs, which could overcome the limitation of four electron transfer steps in OER. Especially, the proper Fe-Co distance and steric direction of the planar-Fe-Co benefit the cooperation of dual sites to dehydrogenate intermediates into *O-O* than stereo-Fe-Co in the rate-determining step. This work provides valuable insights and support for further research and development of OER dual-site catalysts.

Surface-Reconstructed Ru-Doped Nickel/Iron Oxyhydroxide Arrays for Efficient Oxygen Evolution

The generation of an active phase through dynamic surface reconstruction is a promising strategy for improving the activity of electrocatalysts. However, studies investigating the reconstruction process and its impact on the intrinsic properties of the catalysts are scarce. Herein, the surface reconstruction of NiFe2 O4 interfaced with NiMoO4 (Ru-NFO/NMO) facilitated by Ru doping is reported. The electrochemical and material characterizations demonstrate that Ru doping can regulate the electronic structure of NFO/NMO and induce the high-valence state of Ni3.6+ δ , facilitating the surface reconstruction to highly active Ru-doped NiFeOOH/NiOOH (SR-Ru-NFO/NMO). The optimized SR-Ru-NFO/NMO exhibits promising performance in the oxygen evolution reaction, displaying a low overpotential of 229 mV at 10 mA cm-2 and good stability at varying current densities for 80 h. Density functional theory calculations indicate that Ru doping can increase the electron density and optimize intermediate adsorption by shifting the d-band center downward. This work provides valuable insights into the tuning of electrocatalysts by surface reconstruction and offers a rational design strategy for the development of highly active oxygen evolution reaction electrocatalysts.

Light-driven assembly of Pt clusters on Mo-NiOx nanosheets to achieve Pt/Mo-NiOx hybrid with dense heterointerfaces and optimized charge redistribution for alkaline hydrogen evolution

Designing cost-effective alkaline hydrogen evolution reaction (HER) catalysts with high water dissociation ability, enhanced hydroxyl transfer rate and optimized hydrogen adsorption free energy (ΔGH*) by a time and energy efficient strategy is pivotal, but still challenging for alkaline water electrolysis. Herein, Pt/Mo-NiOx hybrid consisting of Pt clusters assembled on Mo-doped NiOx nanosheet arrays is prepared on the surface of raw NiMo foam (NMF) by a light-driven strategy to address this challenge. Benefitting from the electronic interaction between Mo-NiOx and Pt, the Pt/Mo-NiOx composite owns optimized ΔGH* and is beneficial for accelerating water dissociation and hydroxyl transfer. As a result, the optimized Pt/Mo-NiOx/NMF electrode displays an exceptional alkaline HER activity with a low overpotential of 62 mV to obtain 100 mA cm-2 and a high Pt mass activity (13.2 times as high as that of commercial 20 wt% Pt/C). Furthermore, the assembled two-electrode cell of Pt/Mo-NiOx/NMF||NiFe-LDH/NF requires a voltage of only 1.549 V to deliver 100 mA cm-2, along with negligible activity decay after 70 h stability test. The present study provides a promising strategy for exploiting high-performance electrocatalysts towards alkaline HER.

Progress in Anode Stability Improvement for Seawater Electrolysis to Produce Hydrogen

Seawater electrolysis for hydrogen production is a sustainable and economical approach that can mitigate the energy crisis and global warming issues. Although various catalysts/electrodes with excellent activities have been developed for high-efficiency seawater electrolysis, their unsatisfactory durability, especially for anodes, severely impedes their industrial applications. In this review, attention is paid to the factors that affect the stability of anodes and the corresponding strategies for designing catalytic materials to prolong the anode's lifetime. In addition, two important aspects-electrolyte optimization and electrolyzer design-with respect to anode stability improvement are summarized. Furthermore, several methods for rapid stability assessment are proposed for the fast screening of both highly active and stable catalysts/electrodes. Finally, perspectives on future investigations aimed at improving the stability of seawater electrolysis systems are outlined.

Metal nitrides for seawater electrolysis

Electrocatalytic high-throughput seawater electrolysis for hydrogen production is a promising green energy technology that offers possibilities for environmental and energy sustainability. However, large-scale application is limited by the complex composition of seawater, high concentration of Cl- leading to competing reaction, and severe corrosion of electrode materials. In recent years, extensive research has been conducted to address these challenges. Metal nitrides (MNs) with excellent chemical stability and catalytic properties have emerged as ideal electrocatalyst candidates. This review presents the electrode reactions and basic parameters of the seawater splitting process, and summarizes the types and selection principles of conductive substrates with critical analysis of the design principles for seawater electrocatalysts. The focus is on discussing the properties, synthesis, and design strategies of MN-based electrocatalysts. Finally, we provide an outlook for the future development of MNs in the high-throughput seawater electrolysis field and highlight key issues that require further research and optimization.

Oxygen-Bridged Cobalt-Chromium Atomic Pair in MOF-Derived Cobalt Phosphide Networks as Efficient Active Sites Enabling Synergistic Electrocatalytic Water Splitting in Alkaline Media

Electrochemical water splitting offers a most promising pathway for "green hydrogen" generation. Even so, it remains a struggle to improve the electrocatalytic performance of non-noble metal catalysts, especially bifunctional electrocatalysts. Herein, aiming to accelerate the hydrogen and oxygen evolution reactions, an oxygen-bridged cobalt-chromium (Co-O-Cr) dual-sites catalyst anchored on cobalt phosphide synthesized through MOF-mediation are proposed. By utilizing the filling characteristics of 3d orbitals and modulated local electronic structure of the catalytic active site, the well-designed catalyst requires only an external voltage of 1.53 V to deliver the current density of 20 mA cm-2 during the process of water splitting apart from the superb HER and OER activity with a low overpotential of 87 and 203 mV at a current density of 10 mA cm-2 , respectively. Moreover, density functional theory (DFT) calculations are utilized to unravel mechanistic investigations, including the accelerated adsorption and dissociation process of H2 O on the Co-O-Cr moiety surface, the down-shifted d-band center, a lowered energy barrier for the OER and so on. This work offers a design direction for optimizing catalytic activity toward energy conversion.

Ligand-engineered Ru-doped cobalt oxides derived from metal-organic frameworks for large-current-density water splitting

The influence of the preorganized structure and chemical composition of metal-organic frameworks (MOFs) on the morphology, surface properties, and catalytic activity of the MOFs-derived metal oxides is yet to be revealed. In this work, two types of Co-MOFs with different coordination configurations are synthesized for the preparation of the structure-engineered ruthenium (Ru)-doped cobalt oxides. The effect of the preorganized coordination structure of the MOFs on the morphology and surface properties is investigated. Interestingly, the oxalate-based MOFs derived Ru-doped cobalt oxide (OX-Co3O4-Ru) exhibits much better surface wettability and more oxygen vacancies than the zeolitic imidazolate framework-67 derived Ru-doped cobalt oxide. As expected, the OX-Co3O4-Ru owns excellent catalytic properties towards both hydrogen evolution reaction and oxygen evolution reaction with an overpotential of 49 and 286 mV, respectively at a current density of 100 mA cm-2 in 1.0 M KOH. Importantly, the bifunctional OX-Co3O4-Ru catalyst offers an extremely high current density of 500 mA cm-2 at a cell voltage of 1.71 V for overall water splitting and as well demonstrates robust working stability.

Controlling the electronic structure of Fe-MOF electrocatalyst for enhanced water splitting and urea oxidation: A plasma-assisted approach

The design of high-performance electrocatalysts for water splitting and urea oxidation reactions requires effective regulation of their electronic structure and electrochemical surface area (ECSA). In this study, we developed an in-situ grown Fe-MOF electrocatalyst on Fe foam (FF) by using a combination of easy hydrothermal synthesis and advanced plasma technology (Fe-MOF/FF). By varying the plasma treatment time, we could tailor the surface morphology and electronic structure of the Fe-MOF/FF microrods. Meanwhile, density functional theory (DFT) calculations investigated the catalytic mechanism, revealing that plasma-treated Fe-MOF/FF has a lower energy barrier for water splitting and H* adsorption during the HER process, and higher catalytic activity for UOR. Additionally, the electronic density of optimized Fe-MOF/FF is significantly expanded near the Fermi level. Remarkably, our catalysts achieved exceptional activity in both water splitting and urea electrolysis, requiring only 1.54 V and 1.472 V, respectively, at 10 mA cm-2, with excellent stability. Our findings highlight the potential of plasma technology as a powerful tool for developing multifunctional electrocatalysts for clean energy and industrial wastewater treatment applications.

Enhanced Metal-Support Interactions Boost the Electrocatalytic Water Splitting of Supported Ruthenium Nanoparticles on a Ni3 N/NiO Heterojunction at Industrial Current Density

Developing highly efficient and stable hydrogen production catalysts for electrochemical water splitting (EWS) at industrial current densities remains a great challenge. Herein, we proposed a heterostructure-induced-strategy to optimize the metal-support interaction (MSI) and the EWS activity of Ru-Ni3 N/NiO. Density functional theory (DFT) calculations firstly predicted that the Ni3 N/NiO-heterostructures can improve the structural stability, electronic distributions, and orbital coupling of Ru-Ni3 N/NiO compared to Ru-Ni3 N and Ru-NiO, which accordingly decreases energy barriers and increases the electroactivity for EWS. As a proof-of-concept, the Ru-Ni3 N/NiO catalyst with a 2D Ni3 N/NiO-heterostructures nanosheet array, uniformly dispersed Ru nanoparticles, and strong MSI, was successfully constructed in the experiment, which exhibited excellent HER and OER activity with overpotentials of 190 mV and 385 mV at 1000 mA cm-2 , respectively. Furthermore, the Ru-Ni3 N/NiO-based EWS device can realize an industrial current density (1000 mA cm-2 ) at 1.74 V and 1.80 V under alkaline pure water and seawater conditions, respectively. Additionally, it also achieves a high durability of 1000 h (@ 500 mA cm-2 ) in alkaline pure water.

Ultralow ruthenium modification of cobalt metal-organic frameworks for enhanced efficient bifunctional water splitting

Hydrogen economy has emerged as a promising alternative to the current hydrocarbon economy. It involves harvesting renewable energy to split water into hydrogen and oxygen and then further utilising clean hydrogen fuel for various applications. The rational exploration of advanced non-precious metal bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for efficient water splitting. Herein, an ultralow Ru-modified cobalt metal-organic framework (CoRu0.06-MOF/NF) two-dimensional nanosheet array bifunctional catalyst was fabricated through a strategy under mild experimental conditions. The obtained CoRu0.06-MOF/NF exhibited excellent bifunctional electrocatalytic activity and stability in alkaline media, with low overpotentials of 37 and 181 mV and significant durability for more than 95 and 110 h toward the HER and OER at 10 mA cm-2, respectively. The experimental results showed that the two-dimensional nanoarray structure had a large specific surface area and abundant exposed active sites. Additionally, ultralow Ru modification optimized the electronic structure and improved the conductivity of the cobalt metal-organic frameworks, thereby reducing the energy barrier of the rate-limiting step and accelerating the water splitting reaction.

Application of Oxygen-Group-Based Amorphous Nanomaterials in Electrocatalytic Water Splitting

Environmentally friendly energy sources (e.g., hydrogen) require an urgent development targeting to address the problem of energy scarcity. Electrocatalytic water splitting is being explored as a convenient catalytic reaction in this context, and promising amorphous nanomaterials (ANMs) are receiving increasing attention due to their excellent catalytic properties.Oxygen group-based amorphous nanomaterials (O-ANMs) are an important component of the broad family of ANMs due to their unique amorphous structure, large number of defects, and abundant randomly oriented bonds, O-ANMs induce the generation of a larger number of active sites, which favors a better catalytic activity. Meanwhile, amorphous materials can disrupt the inherent features of conventional crystalline materials regarding electron transfer paths, resulting in higher flexibility. O-ANMs mainly include VIA elements such as oxygen, sulfur, selenium, tellurium, and other transition metals, most of which are reported to be free of noble metals and have comparable performance to commercial catalysts Pt/C or IrO2 and RuO2 in electrocatalysis. This review covers the features and reaction mechanism of O-ANMs, the synthesis strategies to prepare O-ANMs, as well as the application of O-ANMs in electrocatalytic water splitting. Last, the challenges and prospective remarks for future development in O-ANMs for electrocatalytic water splitting are concluded.

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

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

Fe-Regulated Amorphous-Crystal Ni(Fe)P2 Nanosheets Coupled with Ru Powerfully Drive Seawater Splitting at Large Current Density

Water electrolysis is an ideal method for industrial green hydrogen production. However, due to increasing scarcity of freshwater, it is inevitable to develop advanced catalysts for electrolyzing seawater especially at large current density. This work reports a unique Ru nanocrystal coupled amorphous-crystal Ni(Fe)P2 nanosheet bifunctional catalyst (Ru-Ni(Fe)P2 /NF), caused by partial substitution of Fe to Ni atoms in Ni(Fe)P2 , and explores its electrocatalytic mechanism by density functional theory (DFT) calculations. Owing to high electrical conductivity of crystalline phases, unsaturated coordination of amorphous phases, and couple of Ru species, Ru-Ni(Fe)P2 /NF only requires overpotentials of 375/295 and 520/361 mV to drive a large current density of 1 A cm-2 for oxygen/hydrogen evolution reaction (OER/HER) in alkaline water/seawater, respectively, significantly outperforming commercial Pt/C/NF and RuO2 /NF catalysts. In addition, it maintains stable performance at large current density of 1 A cm-2 and 600 mA cm-2 for 50 h in alkaline water and seawater, respectively. This work provides a new way for design of catalysts toward industrial-level seawater splitting.

Collaborative Interface Optimization Strategy Guided Ultrafine RuCo and MXene Heterostructure Electrocatalysts for Efficient Overall Water Splitting

Developing highly active and robust electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) is crucial for the large-scale utilization of green hydrogen. In this study, a collaborative interface optimization guided strategy was employed to prepare a metal-organic framework (MOF) derived heterostructure electrocatalyst (MXene@RuCo NPs). The obtained electrocatalyst requires overpotentials of only 20 mV for the HER and 253 mV for the OER to deliver a current density of 10 mA/cm² in alkaline media, respectively, and it also exhibits great performance at high current density. Experiments and theoretical calculations reveal that the doped Ru introduces second active sites and decreases the diameter of nanoparticles, which greatly enhances the number of active sites. More importantly, the MXene/RuCo NPs heterogeneous interfaces in the catalysts exhibit great synergistic effects, decreasing the work function of the catalyst and improving the charge transfer rate, thus reducing the energy barrier of the catalytic reaction. This work represents a promising strategy for the development of MOF-derived highly active catalysts to achieve efficient energy conversion in industrial applications.

High-Performance Bifunctional Porous Iron-Rich Phosphide/Nickel Nitride Heterostructures for Alkaline Seawater Splitting

Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low-cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non-noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron-rich bimetallic phosphide nanoparticles on metallic Ni₃ N (Fe_{2-2 x} Co_{2 x} P/Ni₃ N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe_0.74 Co_0.26 )₂ P/Ni₃ N and Fe₂ P/Ni₃ N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm^-2 for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm^-2 with 1.592/1.645 V. Particularly, Fe₂ P/Ni₃ N displays an unprecedented overpotential of 302 mV at 500 mA cm^-2 , which represents the best alkaline seawater oxygen evolution activity among the ever-reported non-noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm^-2 with 1.701/1.768 V, surpassing most of the reported non-noble lectrocatalysts. This work provides a new approach for developing high-performance electrocatalysts for seawater splitting.

Flower-Like Amorphous MoO3- x Stabilized Ru Single Atoms for Efficient Overall Water/Seawater Splitting

Benefitting from the maximum atom utilization efficiency, special size quantum effects and tailored active sites, single-atom catalysts (SACs) have been promising candidates for bifunctional catalysts toward water splitting. Besides, due to the unique structure and properties, some amorphous materials have been found to possess better performance than their crystalline counterparts in electrocatalytic water splitting. Herein, by combining the advantages of ruthenium (Ru) single atoms and amorphous substrates, amorphous molybdenum-based oxide stabilized single-atomic-site Ru (Ru SAs-MoO_{3- x} /NF) catalysts are conceived as a self-supported electrode. By virtue of the large surface area, enhanced intrinsic activity and fast reaction kinetics, the as-prepared Ru SAs-MoO_{3- x} /NF electrode effectively drives both oxygen evolution reaction (209 mV @ 10 mA cm^-2 ) and hydrogen evolution reaction (36 mV @ 10 mA cm^-2 ) in alkaline media. Impressively, the assembled electrolyzer merely requires an ultralow cell voltage of 1.487 V to deliver the current density of 10 mA cm^-2 . Furthermore, such an electrode also exhibits a great application potential in alkaline seawater electrolysis, achieving a current density of 100 mA cm^-2 at a low cell voltage of 1.759 V. In addition, Ru SAs-MoO_{3- x} /NF only has very small current density decay in the long-term constant current water splitting test.

IrPd Nanoalloy-Structured Bifunctional Electrocatalyst for Efficient and pH-Universal Water Splitting

The lack of high efficiency and pH-universal bifunctional electrocatalysts for water splitting to hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hinders the large-scale production of green hydrogen. Here, an IrPd electrocatalyst supported on ketjenblack that exhibits outstanding bifunctional performance for both HER and OER at wide pH conditions is presented. The optimized IrPd catalyst exhibits a specific activity of 4.46 and 3.98 A mg_Ir ^-1 in the overpotential of 100 and 370 mV for HER and OER, respectively, in alkaline conditions. When applied to the anion exchange membrane electrolyzer, the Ir₄₄ Pd₅₆ /KB catalyst shows a stability of >20 h at a current of 250 mA cm^-2 for water decomposition, indicating promising prospects for practical applications. Beyond offering an advanced electrocatalyst, this work also guides the rational design of desirable bifunctional electrocatalysts for HER and OER by regulating the microenvironments and electronic structures of metal catalytic sites for diverse catalysis.

Design Strategy of Corrosion-Resistant Electrodes for Seawater Electrolysis

Electrocatalytic water splitting for hydrogen (H₂) production has attracted more and more attention in the context of energy shortages. The use of scarce pure water resources, such as electrolyte, not only increases the cost but also makes application difficult on a large scale. Compared to pure water electrolysis, seawater electrolysis is more competitive in terms of both resource acquisition and economic benefits; however, the complex ionic environment in seawater also brings great challenges to seawater electrolysis technology. Specifically, chloride oxidation-related corrosion and the deposition of insoluble solids on the surface of electrodes during seawater electrolysis make a significant difference to electrocatalytic performance. In response to this issue, design strategies have been proposed to improve the stability of electrodes. Herein, basic principles of seawater electrolysis are first discussed. Then, the design strategy for corrosion-resistant electrodes for seawater electrolysis is recommended. Finally, a development direction for seawater electrolysis in the industrialization process is proposed.

Rational Synthesis of Core-Shell-Structured Nickel Sulfide-Based Nanostructures for Efficient Seawater Electrolysis

Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing chlorine evolution, and catalyst poisoning. Hereto, the core-shell-structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni₃ S₂ nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000 mA cm^-2 at the overpotential of 341 mV in 1.0 m KOH seawater. The feasible surface reconstruction of Ni₃ S₂ -FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni₃ S₂ nanopyramids coated with FeNi₂ P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0 m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636 V to attain 100 mA cm^-2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater.

Pt nanoclusters on GaN nanowires for solar-asssisted seawater hydrogen evolution

Seawater electrolysis provides a viable method to produce clean hydrogen fuel. To date, however, the realization of high performance photocathodes for seawater hydrogen evolution reaction has remained challenging. Here, we introduce n⁺-p Si photocathodes with dramatically improved activity and stability for hydrogen evolution reaction in seawater, modified by Pt nanoclusters anchored on GaN nanowires. We find that Pt-Ga sites at the Pt/GaN interface promote the dissociation of water molecules and spilling H* over to neighboring Pt atoms for efficient H₂ production. Pt/GaN/Si photocathodes achieve a current density of -10 mA/cm² at 0.15 and 0.39 V vs. RHE and high applied bias photon-to-current efficiency of 1.7% and 7.9% in seawater (pH = 8.2) and phosphate-buffered seawater (pH = 7.4), respectively. We further demonstrate a record-high photocurrent density of ~169 mA/cm² under concentrated solar light (9 suns). Moreover, Pt/GaN/Si can continuously produce H₂ even under dark conditions by simply switching the electrical contact. This work provides valuable guidelines to design an efficient, stable, and energy-saving electrode for H₂ generation by seawater splitting.

Electronic Structure Modulation Induced by Cobalt-doping and Lattice-Contracting on Armor-Like Ruthenium Oxide Drives pH-Universal Oxygen Evolution

Exquisite design of RuO₂ -based catalysts to simultaneously improve activity and stability under harsh conditions and reduce the Ru dosage is crucial for advancing energy conversion involving oxygen evolution reaction (OER). Herein, a distinctive cobalt-doped RuO_x framework is constructed on Co₃ O₄ nanocones (Co₃ O₄ @CoRuO_x ) as a promising strategy to realize above urgent desires. Extensive experimental characterization and theoretical analysis demonstrate that cobalt doped in RuO_x lattice brings the oxygen vacancies and lattice contraction, which jointly redistribute the electron configuration of RuO_x . The optimized d-band center balances the adsorption energies of oxygenated intermediates, lowing the thermodynamical barrier of the rate-determining step; and meanwhile, the over-oxidation and dissolution of Ru species are restrained because of the p-band down-shifting of the lattice oxygen. Co₃ O₄ @CoRuO_x with 3.7 wt.% Ru delivers the extremely low OER overpotentials at 10 mA cm^-2 in alkaline (167 mV), neutral (229 mV), and acidic electrolytes (161 mV), and super operating stability over dozens of hours. The unprecedented activity ranks first in all pH-universal OER catalysts reported so far. These findings provide a route to produce robust low-loading Ru catalysts and an engineering approach for regulating the central active metal through synergy of co-existing defects to improve the catalytic performance and stability.

General Synthesis of MOF Nanotubes via Hydrogen-Bonded Organic Frameworks toward Efficient Hydrogen Evolution Electrocatalysts

The application scope of metal-organic frameworks (MOFs) can be extended by rationally designing the architecture and components of MOFs, which can be achieved via a metal-containing solid templated strategy. However, this strategy suffers from low efficiency and provides only one specific MOF from one template. Herein, we present a versatile templated strategy in which organic ligands are weaved into hydrogen-bonded organic frameworks (HOFs) for the controllable and scalable synthesis of MOF nanotubes. HOF nanowires assembled from benzene-1,3,5-tricarboxylic acid and melamine via a simple sonochemical approach serve as both the template and precursor to produce MOF nanotubes with varied metal compositions. Hybrid nanotubes containing nanometal crystals and N-doped graphene prepared through a carbonization process show that the optimized NiRuIr alloy@NG nanotube exhibits excellent electrocatalytic HER activity and durability in alkaline media, outperforming most reported catalysts. The strategy proposed here demonstrates a pioneering study of combination of HOF and MOF, which shows great potential in the design of other nanosized MOFs with various architectures and compositions for potential applications.

Coupling Transition Metal Catalysts with Ir for Enhanced Electrochemical Water Splitting Activity

Developing advanced electrocatalysts is of great significance for boosting electrochemical water splitting to produce hydrogen. The electrocatalytic activity of a catalyst is associated with the surface/interface, geometric structure, and electronic properties. Coupling Ir with transition metal compounds is an effective strategy to improve their electrocatalytic performance. In this review, we summarize the recent progress of Ir coupled transition metal compound catalysts for the application in driving electrochemical water splitting. The significant role of Ir played in the promotion of electrocatalytic performance is firstly illustrated. Then, the applications of Ir-based catalysts in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are comprehensively discussed, with an emphasis on correlating the structure-function relationships. Lastly, the challenges and future directions for the fabrication of more advanced Ir coupled electrocatalysts are also presented.

Hollow Nanowire Constructed by NiCo Doped RuO2 Nanoparticles for Robust Hydrogen Evolution at High-Current-Density

Large-current-density electrocatalytic water splitting is essential for industrial hydrogen production, but it is currently hindered by lacking active and robust hydrogen evolution reaction (HER) catalysts. Herein, a novel electrode of hollow nanowire arrays constructed by NiCo modified RuO₂ nanoparticles on Ni foam (NiCo@RuO₂ HNAs/NF) for high-performance HER was reported. Such efficient electrode was fabricated by ion exchange with NF-supported Ni modified cobalt carbonate hydroxide nanowire arrays template (Ni@CoCH NAs/NF). The formed NiCo@RuO₂ HNAs/NF only needed overpotentials of 148.5 and 236.1 mV to deliver 500 and 1000 mA cm^-2 , respectively, along with excellent stability at the high-current-density for 300 h. Such remarkable HER performance was mainly attributed to the hollow structure with high surface area, hydrophilic feature, and NiCo@RuO₂ with optimized hydrogen evolution kinetics. After coupling with anodic Ni@CoCH NAs/NF, our electrolyzer outperformed Pt/C-IrO₂ and most other Ru-based electrolyzers. This work provides a promising Pt alternative catalyst for profitable H₂ production.

Coupling Amorphous Ni Hydroxide Nanoparticles with Single-Atom Rh on Cu Nanowire Arrays for Highly Efficient Alkaline Seawater Electrolysis

Exploring efficient catalysts for alkaline seawater electrolysis is highly desired yet challenging. Herein, coupling single-atom rhodium with amorphous nickel hydroxide nanoparticles on copper nanowire arrays is designed as a new active catalyst for the highly efficient alkaline seawater electrolysis. We found that an amorphous Ni(OH)₂ nanoparticle is an effective catalyst to accelerate the water dissociation step. In contrast, the single-atom rhodium is an active site for adsorbed hydrogen recombination to generate H₂. The NiRh-Cu NA/CF catalyst shows superior electrocatalytic activity toward HER, surpassing a benchmark Pt@C. In detail, the NiRh-Cu NA/CF catalyst exhibits HER overpotentials as low as 12 and 21 mV with a current density of 10 mA cm^-2 in fresh water and seawater, respectively. At high current density, the NiRh-Cu NA/CF catalyst also exhibits an outstanding performance, where 300 mA cm^-2 can be obtained at an overpotential of 155 mV and shows a slight fluctuation in the current density over 30 h.

Rational Regulation of Crystalline/Amorphous Microprisms-Nanochannels Based on Molecular Sieve (VSB-5) for Electrochemical Overall Water Splitting

Rational regulation of the composition and structure of electrocatalysts is crucial to the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a new electrocatalyst of nickel phosphate microprism (VSB/NiPO) is developed via a simple solvothermal reaction. The microprism is mainly composed of Versailles-Santa Barbara-5 (VSB-5, molecular sieve) with unique nanochannels, which contribute to accelerating mass transfer and exposing more active sites, thus displaying excellent HER activity. Subsequently, the crystallinity and electronic structure of the framework are modulated by incorporating Fe with the combination of calcination and impregnation. The nanochannels are converted to the amorphous arrangement, and the Ni centers are regulated to the higher valence. The resultant Fe-VSB/NiPO-500 exhibits a low OER overpotential of 227 mV at 50 mA cm^-2 . Interestingly, an integrated electrolyzer assembled by VSB/NiPO(-) and Fe-VSB/NiPO-500(+) performs well for overall water splitting, which requires only 1.487 V to achieve 10 mA cm^-2 , and remains stable at 100 mA cm^-2 over 100 h. This finding opens a new avenue for developing VSB-5 in the field of electrocatalysis.

Recent Advances on Hydrogen Evolution and Oxygen Evolution Catalysts for Direct Seawater Splitting

Producing hydrogen via water electrolysis could be a favorable technique for energy conversion, but the freshwater shortage would inevitably limit the industrial application of the electrolyzers. Being an inexhaustible resource of water on our planet, seawater can be a promising alternative electrolyte for industrial hydrogen production. However, many challenges are hindering the actual application of seawater splitting, especially the competing reactions relating to chlorine at the anode that could severely corrode the catalysts. The execution of direct seawater electrolysis needs efficient and robust electrocatalysts that can prevent the interference of competing reactions and resist different impurities. In recent years, researchers have made great advances in developing high-efficiency electrocatalysts with improved activity and stability. This review will provide the macroscopic understanding of direct seawater splitting, the strategies for rational electrocatalyst design, and the development prospects of hydrogen production via seawater splitting. The nonprecious metal-based electrocatalysts for stable seawater splitting and their catalytic mechanisms are emphasized to offer guidance for designing the efficient and robust electrocatalyst, so as to promote the production of green hydrogen via seawater splitting.