Recent Advances in Design of Electrocatalysts for High-Current-Density Water Splitting

Integrated electrode design based on metal-organic frameworks for anion exchange membrane electrolyzers under high current densities

The development of efficient and durable electrodes is crucial for realizing industrialized hydrogen production via anion exchange membrane water electrolyzers (AEMWEs). However, limited attention has been given to preparing three-dimensional integrated electrodes through the coupling of gas diffusion layers and catalyst layers. Herein, an iron-cobalt (FeCo) gallate metal-organic framework (MOF) is controllably deposited on nickel foam (denotedas FeCo-gallatex/NF), serving as both the integrated cathode and anode of AEMWEs. These electrodes consist of MOF-coated catalyst layers and uncoated regions of the NF substrate serving as gas diffusion layers, where the anchored MOF material exhibits dual functionality as a catalyst for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). This integrated electrode design significantly reduces the ohmic and mass transport resistances, while improving the kinetics. Consequently, the proposed electrode exhibits impressive performance for both OER and HER under alkaline conditions, enabling efficient overall water splitting. Additionally, the assembled AEMWEs achieve a small potential of only 1.63 V at 1 A cm-2, along with durable stability for 800 h at the same current density. This work provides an innovative idea for developing high-performance and durable electrodes of AEMWEs.

3D-Printed Metal Electrodes with Enhanced Bubble Removal for Efficient Water Electrolysis

Improving the water electrolysis efficiency at high current densities is constrained by the structure of available foam and mesh electrodes, which suffer from internal bubble entrapment. Herein, we used laser powder bed fusion-based 3D printing to fabricate Schwarz Diamond (SD) structure nickel electrodes for water electrolysis. After loading with NiMoFeOx as the oxygen evolution reaction catalyst and MoNi4-MoO2 as the hydrogen evolution reaction catalyst, the anion exchange membrane water electrolyzer utilizing SD nickel electrodes achieved a current density of 1 A cm-2 at 1.74 V, outperforming conventional nickel foam and mesh electrode-based electrolyzers in the same conditions and demonstrated durable operation for more than 1000 h. In-situ observations of bubble evolution in the electrolyzer and single-frequency impedance spectra reveal that the 3D-printed SD structure exhibits highly efficient bubble/liquid transport. The present study investigates the potential of 3D printing technology in the fabrication of metallic porous electrodes for efficient water electrolysis.

Carbon-Supported Single Fe/Co/Ni Atom Catalysts for Water Oxidation: Unveiling the Dynamic Active Sites

Extensive research has been conducted on carbon-supported single-atom catalysts (SACs) for electrochemical applications, owing to their outstanding conductivity and high metal atom utilization. The atomic dispersion of active sites provides an ideal platform to investigate the structure-performance correlations. Despite this, the development of straightforward and scalable synthesis methods, along with the tracking of the dynamic active sites under catalytic conditions, remains a significant challenge. Herein, we introduce a biomass-inspired coordination confinement strategy to construct a series of carbon-supported SACs, incorporating various metal elements, such as Fe, Co, and Ni. We have systematically characterized their electronic and geometric structure using various spectroscopic and microscopic techniques. Through in situ X-ray absorption spectroscopy (XAS), atomic scanning transmission electron microscopy (STEM), and electron paramagnetic resonance (EPR) analyses, it is demonstrated that the single atoms undergo structural rearrangement to form amorphous (oxy)hydroxide clusters during oxygen evolution reaction (OER), where the newly formed oxygen-bridged dual metal M─O─M or M─O─M' (M/M' = Fe, Co, Ni) moieties within these clusters play key role in the OER performance. This work provides essential insights into tracking the actual active sites of SACs during electrochemical OER.

V doped hollow Co3O4 nanoprisms with a modulated electronic structure for high-performance oxygen evolution reaction

The sluggish oxygen evolution reaction (OER) kinetics in water splitting makes it crucial to design highly active OER catalysts. Spinel oxides are considered as promising candidates due to their various compositions, valence states and electronic configurations. This paper reports a facile procedure to prepare V-doped hollow Co3O4 nanoprisms for the OER. The introduction of V can effectively modulate the electronic structure of Co3O4, therefore improving its intrinsic catalytic activity. The hollow prismatic structure ensures the exposure of catalytically active sites and rapid mass transport, thereby improving the extrinsic catalytic activity. As a result, optimized V-Co3O4-5 exhibits a small overpotential of 288 mV at 10 mA cm-2 with good durability. This work provides an innovative direction for designing efficient OER electrocatalysts via heteroatom doping.

Geography-guided industrial-level upcycling of polyethylene terephthalate plastics through alkaline seawater-based processes

The escalating plastic crisis can be mitigated by upgrading waste polyethylene terephthalate (PET). Leveraging the geographical advantages of offshores with established chlor-alkali industries, abundant renewable energy, and extensive seawater, we here present a technically and economically viable strategy of harnessing natural seawater as a medium to transform PET plastics into high-value chemicals. We report a nickel-molybdenum catalyst incorporating frustrated Lewis pairs for the efficient breakage of C─C bond and the oxidation of ethylene glycol, which sustains a current of 6 amperes at 1.74 volts over 350 hours, with a projected revenue of approximately $304 United States dollar (USD) per ton of processed PET plastics. In a customized electrolyzer, we successfully convert 301.0 grams of waste PET into 227.1 grams of p-phthalic acid (95.5% yield), 1486.2 grams of potassium diformate (67.2% yield), and approximately 214.9 liters of green hydrogen. This study paves the way for scalable PET upcycling, contributing to a circular economy and mitigating the plastic pollution crisis.

Synthesis of noble metal nanoarrays via agglomeration and metallurgy for acidic water electrolysis

Noble metal electrocatalysts remain the mainstay for proton exchange membrane water electrolysis, majorly due to their exceptional activity and durability in acidic media. However, conventional powder and particle catalysts intensively suffer from aggregation, shedding and poor electron conductivity in practical applications. Here, we develop a micellar brush-guided method to agglomerate and smelt metal nanoparticles into erect nanoarrays with designable constitutions on various substrates. While the nanoarrays of stacked nanoparticles show poor stability in the acidic media, the smelting treatment substantially enhances the electron conductivity by more than four order of magnitude and reinforces the nanoarray architectures. This allows the tailored fabrication of self-supported acid-durable metallic and alloy nanoarray catalysts with outstanding hydrogen evolution activity, and metal oxide nanoarray with extraordinary oxygen evolution activity. The integration of metallic Ru-nanoarray and RuOx-nanoarray in a proton exchange membrane electrolyzer further enables a long-term stable water electrolysis process for more than 500 h at 1 A cm-2.

Facile One-Step Fabrication of 1T-Phase-Rich Bimetallic CoFe Co-Doped MoS2 Nanoflower: Synergistic Engineering for Bi-Functional Water Splitting Electrocatalysis

MoS2 has emerged as a highly promising catalyst for the hydrogen evolution reaction (HER) owing to its exceptional catalytic properties. However, there is a pressing need to further enhance its reactivity and integrate oxygen evolution reaction (OER) capabilities to facilitate its industrial implementation. In this context, a dual-metal doping approach presents a straightforward and effective strategy to achieve superior catalytic performance. Systematic characterization and electrochemical evaluations reveal that the synergistic effects of Co and Fe doping significantly enhance both HER and OER activities, demonstrating remarkable potential for practical applications in energy conversion and storage systems. The unique flower-like architecture of the material endows it with a substantially enlarged surface area, which significantly increases the exposure of active sites and facilitates enhanced catalytic activity. Specifically, it achieves the low overpotentials of -127 and 292 mV at 10 mA cm-2 for HER and OER in alkaline media, respectively, and demonstrates excellent stability over a 10 h test. This research provides valuable insights into the development of advanced materials capable of efficiently performing both HER and OER processes, paving the way for potential applications in sustainable energy technologies.

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

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

Electrochemical Hydrogen Production Coupling with the Upgrading of Organic and Inorganic Chemicals

Electrocatalytic water splitting powered by renewable energy is a green and sustainable method for producing high-purity H2. However, in conventional water electrolysis, the anodic oxygen evolution reaction (OER) involves a four-electron transfer process with inherently sluggish kinetics, which severely limits the overall efficiency of water splitting. Recently, replacing OER with thermodynamically favorable oxidation reactions, coupled with the hydrogen evolution reaction, has garnered significant attention and achieved remarkable progress. This strategy not only offers a promising route for energy-saving H₂ production but also enables the simultaneous synthesis of high-value-added products or the removal of pollutants at the anode. Researchers successfully demonstrate the upgrading of numerous organic and inorganic alternatives through this approach. In this review, the latest advances in the coupling of electrocatalytic H2 production and the upgrading of organic and inorganic alternative chemicals are summarized. What's more, the optimization strategy of catalysts, structure-performance relationship, and catalytic mechanism of various reactions are well discussed in each part. Finally, the current challenges and future prospects in this field are outlined, aiming to inspire further innovative breakthroughs in this exciting area of research.

Solar-to-Hydrogen Conversion Efficiency for Photovoltaic Water Electrolysis to Produce Green Hydrogen

Hydrogen is widely regarded as a key energy source for the 21st century, offering sustainability, environmental benefits, and energy storage capacity. Solar-powered water splitting is a frontier technology for green hydrogen production, circumventing reliance on fossil fuels. Advances in solar cells and electrocatalysis have significantly improved hydrogen production via photovoltaic-electrolysis (PV-EC). However, solar-to-hydrogen (STH) conversion efficiency is still limited by factors such as solar cell performance, electrolysis efficiency, and system integration. Optimizing these elements is essential for enhancing overall efficiency. This review focuses on the critical technologies influencing STH efficiency in PV-EC systems. Specifically, the efficiency of photovoltaic devices in harnessing solar energy, the catalytic performance of electrocatalytic materials for efficient water splitting, and the integration of solar cells with electrolyzer systems to optimize overall energy conversion. Furthermore, the latest developments and ongoing challenges in PV-EC water splitting research are explored, evaluating their economic feasibility and offering a perspective on future advancements in photovoltaic water electrolysis.

Recent Advances in Green Hydrogen Production by Electrolyzing Water with Anion-Exchange Membrane

The development of clean and efficient renewable energy is of great strategic importance to realize green energy conversion and low-carbon growth. Hydrogen energy, as a renewable energy with "zero carbon emission", can be efficiently converted into hydrogen energy and electric energy by electrolysis of water to hydrogen technology. Anion-exchange membrane water electrolysis (AEMWE), substantially advanced by nonprecious metal electrocatalysts, is among the most cost-effective and promising water electrolysis technologies, combining the advantages of proton exchange membranes with the proven technology of traditional alkaline water electrolysis and potentially eliminating the disadvantages of both. In this paper, the latest results of AEMWE research in recent years are summarized, including the AEMWE mechanism study and the hot issues of low-cost transition metal hydrogen evolution reaction and oxygen evolution reaction electrocatalyst design in recent years. The key factors affecting the performance of AEMWE are pointed out, and further challenges and opportunities encountered in large-scale industrialization are discussed. Finally, this review provides strong guidance for advancing AEMWE.

Dual Active Site Engineering in Porous NiW Bimetallic Alloys for Enhanced Alkaline Hydrogen Evolution Reaction

Utilizing dual active sites in electrocatalysts creates a synergistic effect, enabling the independent optimization of H2O dissociation and intermediate adsorption/desorption, which in turn enhances the efficiency of the hydrogen evolution reaction (HER). Herein, a porous NiW bimetallic alloy electrocatalyst using a dynamic H2 bubble template (DHBT) strategy is fabricated. This electrocatalyst capitalizes on the synergistic effect of dual active sites, achieving industrial-level current densities of 500 and 1000 mA cm-2 for HER in 1.0 M KOH, with low overpotentials of 198 and 264 mV, respectively. It also demonstrates excellent stability over a 200 h test. Theoretical studies reveal that alloying Ni with W shifts the d-band center (εd) of the W 5d orbital downward, which enhances *OH intermediate desorption and promotes H2O adsorption and dissociation at the W site, leading to increased active site availability. Meanwhile, this shift provides more accessible H* intermediates, further enhancing H2 production at the Ni2W1 hollow site. When the porous NiW bimetallic alloy electrocatalyst is implemented in a solar-driven water splitting system, it achieves a high solar-to-hydrogen (STH) conversion efficiency of 16.59%. This work underscores the effectiveness of dual active site electrocatalysts for sustainable H2 production.

Strategies for industrial-grade seawater electrolysis: from electrocatalysts and device design to techno-economic analysis

Seawater electrolysis offers a promising route for sustainable hydrogen production, utilizing abundant seawater to meet global energy demands while addressing environmental concerns. However, challenges such as inefficiencies, high costs, and reliance on noble metal catalysts hinder its practical implementation. This review examines the fundamental mechanisms of seawater electrolysis, focusing on the hydrogen and oxygen evolution reactions (HER and OER) at industrial-scale current densities. Key strategies for catalyst design, including interfacial engineering, structural optimization, and improved mass and electron transport, to enhance efficiency and stability are discussed. Additionally, device architecture and techno-economic considerations are explored to facilitate scalable, cost-effective deployment. By providing insights into advanced materials and system innovations, this review outlines pathways for integrating seawater electrolysis into large-scale sustainable energy solutions.

Enhancing the hydrogen evolution activity of diiron molecular electrocatalysts by modulating the substituent effect of carbon nanotubes

Designing molecular catalysts to enhance hydrogen evolution activity is both highly significant and challenging. In hydrogenases, the redox group (i.e., [4Fe4S] subcluster) near the catalytic active center (i.e., [2Fe2S] subcluster) plays a crucial role in modulating the enzyme's activity. Inspired by this biological strategy, three carbon-nanotube-supported diiron dithiolato hybrids, which are labeled as CNT-X-ADT (X = N, C, and O), were designed. The activity of the diiron catalytic center was regulated through side-chain substituents (i.e., substituent effects) of CNTs. Notably, a bioinspired diiron molecular compound {(μ-SCH2)2N(CH2CO2C6H4CHO-p)}Fe2(CO)6 (1), which was used to mimic the diiron catalytic active center of hydrogenase enzymes, was first synthesized and then covalently attached to carbon nanotubes to form three target hybrids CNT-X-ADT (X = N, C, and O). The side-chain substituents, designed to mimic the activity of the control group, were linked to CNTs through an amination reaction. Significantly, the hydrogen evolution reaction (HER) properties of the CNT-X-ADT hybrids were systematically investigated and compared using various electrochemical techniques. Compared with CNT-C-ADT that lacks side-chain regulatory ability, the average turnover frequency (TOFH2) of CNT-N-ADT is nearly twice as high and reaches 0.175 s-1 after 5 h electrolysis, and the corresponding turnover number (TONH2) for H2 generation reaches 3.1 × 103. In contrast, the CNT-O-ADT hybrid, due to its electron-withdrawing alkoxy side chain, reduces the electron density of the catalytic center, resulting in the poorest HER performance. Overall, this activity modulation using different side-chain substituents holds great significance for the development and design of metal molecular catalysts.

Synergetic Oxidized Mg and Mo Sites on Amorphous Ru Metallene Boost Hydrogen Evolution Electrocatalysis

Ruthenium (Ru) is considered as a promising catalyst for the alkaline hydrogen evolution reaction (HER), yet its weak water adsorption ability hinders the water splitting efficiency. Herein, a concept of introducing the oxygenophilic MgOx and MoOy species onto amorphous Ru metallene is demonstrated through a simple one-pot salt-templating method for the synergic promotion of water adsorption and splitting to greatly enhance the alkaline HER electrocatalysis. The atomically thin MgOx and MoOy species on Ru metallene (MgOx/MoOy-Ru) show a 15.3-fold increase in mass activity for HER at the potential of 100 mV than that of Ru metallene and an ultralow overpotential of 8.5 mV at a current density of 10 mA cm-2. It is further demonstrated that the MgOx/MoOy-Ru-based anion exchange membrane water electrolyzer can achieve a high current density of 100 mA cm-2 at a remarkably low cell voltage of 1.55 V, and exhibit excellent durability of over 60 h at a current density of 500 mA cm-2. In situ spectroscopy and theoretical simulations reveal that the co-introduction of MgOx and MoOy enhances interfacial water adsorption and splitting by promoting adsorption on oxidized Mg sites and lowering the dissociation energy barrier on oxidized Mo sites.

MXene-Supported Single-Atom Electrocatalysts

MXenes, a novel member of the 2D material family, shows promising potential in stabilizing isolated atoms and maximizing the atom utilization efficiency for catalytic applications. This review focuses on the role of MXenes as support for single-atom catalysts (SACs) for various electrochemical reactions, namely the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). First, state-of-the-art characterization and synthesis methods of MXenes and MXene-supported SACs are discussed, highlighting how the unique structure and tunable functional groups enhance the catalytic performance of pristine MXenes and contribute to stabilizing SAs. Then, recent studies of MXene-supported SACs in different electrocatalytic areas are examined, including experimental and theoretical studies. Finally, this review discusses the challenges and outlook of the utilization of MXene-supported SACs in the field of electrocatalysis.

Regulating Interfacial H2O Activity and H2 Bubbles by Core/Shell Nanoarrays for 800 h Stable Alkaline Seawater Electrolysis

The catalytic activity and stability under high current densities for hydrogen evolution reactions (HER) are impeded by firm adherence and coverage of H2 bubbles to the catalytic sites. Herein, we systematically synthesize core/shell nanoarrays to engineer bubble transport channels, which further remarkably regulate interfacial H2O activity, and swift H2 bubble generation and release. The self-supported catalyst holds uniform ultra-low Ru active sites of 0.38 wt% and promotes the rapid formation of plentiful small H2 bubbles, which are rapidly released by the upright channels, mitigating the blockage of active sites and avoiding surface damage from bubble movements. As a result, these core/shell nanoarrays achieve ultralow overpotentials of 18 and 24 mV to reach 10 mA cm-2 for HER in 1 M KOH freshwater and seawater, respectively. Additionally, the assembled electrolyzer demonstrates stable durability over 800 hours with a high current density of 2 A cm-2 in 1 M KOH seawater. The techno-economic analysis (TEA) indicates that the unit cost of the hydrogen production system is nearly half of the DOE's (Department of Energy) 2026 target. Our work addresses the stability challenges of HER and highlights its potential as a sustainable and economically feasible solution for large-scale hydrogen production of seawater.

Suppressing Mo-Species Leaching in MoOx/A-Ni3S2 Cathode for Stable Anion Exchange Membrane Water Electrolysis at Industrial-Scale Current Density

The development of non-noble metal-based hydrogen evolving reaction (HER) electrocatalysts operating under high current density plays a critical role in the large-scale application of anion exchange membrane water electrolysis (AEM-WE). Herein, a porous and hybrid MoS2/Ni3S2 is synthesized on nickel foam (NF) via a one-step hydrothermal method and studied its reconstruction process during alkaline HER conditions. Experimental results indicated that the MoS2 underwent an oxidative dissolution followed by a dynamic equilibrium between dissolution and redeposition of the amorphous MoOx during HER. Meanwhile, S-vacancy-rich Ni3S2 (A-Ni3S2) is exposed and acts as the real active site for HER. The obtained MoOx/A-Ni3S2 catalyst exhibited high catalytic performance in three-electrode systems and single-cell AEM-WE. Finally, for a long-term durability test in the AEM electrolyzer, a dry cathode method is applied to suppress the Mo species leaching from the MoOx/A-Ni3S2 electrode. Remarkably, the device assembled by MoOx/A-Ni3S2 as the cathode catalyst and NiFe as the anode catalyst demonstrated a high stability of 2500 h at 2 A cm-2 and 40 °C with a small aging rate of 30 µV h-1.

Interfacial engineering of a nanofibrous Ru/Cr2O3 heterojunction for efficient alkaline/acid-universal hydrogen evolution at the ampere level

Interfacial engineering of a heterostructured electrocatalyst is an efficient way to boost hydrogen production, yet it still remains a challenging task to achieve superior performance at ampere-grade current density. Herein, a nanofibrous Ru/Cr2O3 heterojunction is prepared for alkaline/acid-universal hydrogen evolution. Theoretical calculations reveal that the introduction of Cr2O3 modulates the electronic structure of Ru, which is beneficial for *H desorption, resulting in a superior HER performance at ampere-grade current density. Accordingly, the resultant Ru/Cr2O3 catalyst presents an ultra-low overpotential of only 88 mV and a long-term stability of 300 h at 1 A cm-2 in 1 M KOH. Furthermore, it also exhibits a small overpotential of 112 mV and steadily operates for 300 h at 1 A cm-2 in 0.5 M H2SO4. The catalyst outperforms not only the benchmark Pt/C catalyst but also most of the top-performing catalysts reported to date. This study offers a novel conceptual approach for designing highly efficient electrocatalysts that hold significant promise for industrial-scale water splitting applications.

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

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

Interfacial-Free-Water-Enhanced Mass Transfer to Boost Current Density of Hydrogen Evolution

The advancement of water electrolysis highlights the growing importance of electrolyzers capable of operating at high current densities, where mass transfer dynamics plays a crucial role. In the electrode reactions, the interfacial water is a key factor in regulating these dynamics. However, the potential of utilizing interfacial-free water (IFW) to modulate electrode behavior remains underexplored. Herein, we investigate the effect of interfacial water structure on hydrogen evolution reaction (HER) performance across different current density ranges, using designed platinum-coated nickel hydroxide on nickel foam (Pt@Ni(OH)2-NF) electrodes. We reveal that with increasing current density, changes in interfacial water structure alter the rate-determining step of the HER. Pt@Ni(OH)2-NF exhibited excellent performance in alkaline electrolytes, achieving 1000 mA cm-2 at 114 mV overpotential. This study provides a novel approach to optimizing alkaline water electrolysis dynamics by enhancing mass transfer, further paving the way for more efficient and energy-saving hydrogen production.

Sub-4 nm Ru-RuO2 Schottky Nanojunction as a Catalyst for Durable Acidic Water Oxidation

RuO2 with high intrinsic activity for water oxidation is a promising alternative to IrO2 in proton exchange membrane (PEM) electrolyzer, but it suffers from long-term stability issues due to overoxidation. Here, we report a sub-4 nm Ru-RuO2 Schottky nanojunction (Ru-RuO2-SN) prepared by a microwave reaction that exhibits high activity and long-term stability in both three-electrode systems and PEM devices. The lattice strain and charge transfer induced by the metal-oxide SN increase the work function of the Ru-RuO2-SN, optimize the local electronic structure, and reduce the desorption energy of the metal site to the oxygen-containing intermediates; as a result, it leads to the oxide path mechanism (OPM) and inhibits the excessive oxidation of surface ruthenium. The Ru-RuO2-SN requires only 165 mV overpotential to obtain 10 mA·cm-2 with 1400 h stability without obvious activity degradation, achieving a stability number (6.7 × 106) matching iridium-based catalysts. In a PEM electrolyzer with Ru-RuO2-SN as an anode catalyst, only 1.6 V is needed to reach 1.0 A·cm-2 and it shows long-term stability at 100 mA·cm-2 for 1100 h and at 500 mA·cm-2 for 100 h. The reaction mechanism for the high stability of Ru-RuO2-SN was analyzed by density functional theory calculations. This work reports a durable, pure Ru-based water-oxidation catalyst and provides a new perspective for the development of efficient Ru-based catalysts.

Guided electrocatalyst design through in-situ techniques and data mining approaches

Intuitive design strategies, primarily based on literature research and trial-and-error efforts, have significantly contributed to advancements in the electrocatalyst field. However, the inherently time-consuming and inconsistent nature of these methods presents substantial challenges in accelerating the discovery of high-performance electrocatalysts. To this end, guided design approaches, including in-situ experimental techniques and data mining, have emerged as powerful catalyst design and optimization tools. The former offers valuable insights into the reaction mechanisms, while the latter identifies patterns within large catalyst databases. In this review, we first present the examples using in-situ experimental techniques, emphasizing a detailed analysis of their strengths and limitations. Then, we explore advancements in data-mining-driven catalyst development, highlighting how data-driven approaches complement experimental methods to accelerate the discovery and optimization of high-performance catalysts. Finally, we discuss the current challenges and possible solutions for guided catalyst design. This review aims to provide a comprehensive understanding of current methodologies and inspire future innovations in electrocatalytic research.

Lamellar Nanoporous Intermetallic Cobalt-Titanium Multisite Electrocatalyst with Extraordinary Activity and Durability for the Hydrogen Evolution Reaction

Constructing well-defined multisites with high activity and durability is crucial for the development of highly efficient electrocatalysts toward multiple-intermediate reactions. Here we report negative mixing enthalpy caused intermetallic cobalt-titanium (Co3Ti) nanoprecipitates on a lamellar hierarchical nanoporous cobalt skeleton as a high-performance nonprecious multisite electrocatalyst for an alkaline hydrogen evolution reaction. The intermetallic Co3Ti as a robust multisite substantially boosts the reaction kinetics of water dissociation and hydrogen adsorption/combination by unisonous adsorptions of hydrogen and hydroxyl intermediates with proper binding energies. By virtue of a bicontinuous and hierarchical nanoporous cobalt skeleton that enables sufficiently accessible Co3Ti multisites and facilitates electron transfer and ion/molecule transportation, a self-supported nanoporous cobalt-titanium heterogeneous electrode exhibits extraordinary electrocatalytic activity and durability toward the hydrogen evolution reaction in 1 M KOH. It reaches a current density of as high as ∼3.31 A cm-2 at a low overpotential of 200 mV and maintains exceptional stability at ∼1.33 A cm-2 for >1000 h.

Recent Strategies for Ni3S2-Based Electrocatalysts with Enhanced Hydrogen Evolution Performance: A Tutorial Review

Water electrolysis represents one of the most environmentally friendly methods for hydrogen production, while its overall efficiency is primarily governed by the electrocatalyst. Nickel sulfides, e.g., Ni3S2, are considered to be highly promising catalysts for the hydrogen evolution reaction (HER) due to their distinctive chemical structure. However, the practical application of Ni3S2-based electrocatalysts is hindered by unsatisfactory high overpotential in the HER and weakened catalytic performance under alkaline conditions. Therefore, in this regard, further research on Ni3S2-based catalysts is being carried out to tackle these challenges. This review provides a comprehensive survey of the latest advancements in Ni3S2-based in improving the HER performance of Ni3S2-based electrocatalysts. The review may offer some inspiration for the rational design and synthesis of novel transition metal-based catalysts with enhanced water electrolysis performance.

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

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

Interface Charge Transfer of Heteroatom Boron Doping Cobalt and Cobalt Nitride for Boosting Water Oxidation

Designing high-performance transition-metal electrocatalysts with controlled active heterointerfacial sites for catalyzing the electrochemical oxygen evolution reaction (OER) is very desirable but remains a great challenge. Here, a facile strategy for the synthesis of transition-metal nitride-based interfacial electrocatalysts boron-doped cobalt/cobalt nitride (B-Co/Co2N) is demonstrated with optimal heterointerfaces between Co and Co2N electrocatalysts by introducing boron as a dopant to the former. Benefiting from the unique electronegativity of B, the obtained B-Co/Co2N electrocatalysts show excellent OER performance with overpotential inputs of as low as 262 and 310 mV for 10 and 100 mA cm-2, which are 1.4 and 6.6 times higher than those of Co/Co2N with the same potential input, respectively. The experimental and theoretical results demonstrate the role of the B dopant in inducing charge redistribution of Co active sites in the Co/Co2N interfacial region, which results in a downshift of the Co 3d band center, the optimal oxidation state of active sites for *OOH formation, and lower energy barriers. Furthermore, the assembled electrolyzer can steadily produce an industrial-grade current density of 1000 mA cm-2 at a cell voltage input of only 1.81 V for at least 100 h with a Faradaic efficiency near 100%. This study provides a promising strategy for heteroatom-doped interfacial electrocatalysts with high performance for energy and environmental applications.

Multifunctional High-Entropy Alloys and Oxides for Self-Powered Electrocatalytic Nitrate Reduction to Ammonia

High-entropy alloys (HEAs) show high activities toward oxygen reduction reaction (ORR), Zn-air batteries (ZABs) and nitrate reduction reaction (NO3 -RR). In this work, FeNiCoMnRh HEA supported by N-doped carbon frameworks is prepared and showed excellent ORR performance with a half-wave potential (E1/2) of 0.89 V versus RHE, limiting diffusion current (jL) of 5.6 mA cm-2 and better current stability. The HEA-assembled ZAB exhibited a high-power density of 103.8 mW cm-2 with a specific capacity of 790 mAh gZn -1. Also, its oxides presented 77% Faraday efficiency (FE) for ammonia production at -0.3 V versus RHE. Accordingly, our designed ZAB was employed to drive NO3 -RR to construct a self-powered system, which provides an attractive route for low-energy sewage treatment and environmentally friendly preparation of ammonia.

Rapid determination of Se(IV) and tSe in fungal samples by foam electrode-based electrolytic hydride generation coupled atomic fluorescence spectrometry

The key to accurately identifying trace heavy metal elements is to achieve efficient sample introduction while shielding the interference of matrix components. Taking the electrolytic hydride generation (EHG) technology as an example, this paper explored the effects of cathode materials and structural factors on the electrosynthesis of hydrogen selenide (H2Se), particularly on suppressing interference from coexisting components. Systematic electrochemical and spectroscopic tests show that the nickel-based electrode can promote the generation of H2Se, while the multi-layer foam structure with large specific surface area, rich pores and weak gas evolution effect improves the yield and stability of electrosynthesis reaction. Even if the surface state of the electrode changes due to the electrodeposition of high concentration interference ion, the electrochemical behavior of selenium (Se) is basically not affected. After coupling with an atomic fluorescence spectrometer detector, this method has a low detection limit (0.13 μg L-1), a wide linear range (2-100 μg L-1), and stable signal output (RSD, 3.3%, n = 11). With the assistance of high-frequency ultrasound sample extraction and pre-reduction measures, Se(IV) and total Se (tSe) in fungal samples such as mushrooms can be quickly quantified without pre-separation of the matrix. The contribution of this study is to provide an economical and sustainable electrochemical gas separation strategy for spectroscopic quantification of trace and even ultra-trace heavy metal elements in complex matrices.

Tailoring Crystalline States of Alloy Coating for High Current Density and Large Areal Capacity of Zn

Due to issues of hydrogen evolution, corrosion, and uncontrolled deposition behaviors at the Zn anode, the practical implementation of Zn-ion batteries has faced significant obstacles. Very limited attention is directed toward various alloy crystalline states for the Zn anode protection primarily due to the challenge of synthesizing high-quality alloy coatings with diverse crystalline states. In this study, the crystalline state of NiCr alloy coating is precisely manipulated using magnetron sputtering, revealing distinct thermodynamic and kinetic changes induced by variation in the crystalline state. This research emphasizes the fundamental understanding of microstructure dynamics and achieves a highly reversible Zn anode at harsh conditions of high current density (80 mA cm-2) and large areal capacity (40 mAh cm-2), thus enabling high-capacity and longevous pouch battery.

Photonic Sintering as an Electrode Structuring Process to Improve Electrocatalytic Activity and Durability in Anion Exchange Membrane Water Electrolysis

Hydrogen production via water electrolysis is essential for achieving carbon-free energy. However, enhancing the performance of these systems, particularly at the electrode level, remains challenging. Photonic sintering (PS) is proposed as a highly effective post-treatment method for electrodes, highlighting the importance of electrode design and optimization. PS significantly enhances the catalytic activity and durability of spinel-type copper-cobalt oxide-based anodes for the oxygen evolution reaction and Pt@C-based cathodes for the hydrogen evolution reaction, which are attributed to structural and chemical modifications, including active site control, optimized surface chemical bonding, improved catalyst-substrate adhesion, and generation of a reduced surface. PS-treated electrodes maintain well-preserved electrochemical active sites and pore structures, which are crucial for activation polarization and mass transport kinetics. Consequently, an anion exchange membrane water electrolysis cell with PS-treated electrodes achieved 89.57% cell efficiency, 3.91 W cm-2 area-specific power at 1.8 V, and a low degradation rate of 0.049 mV h-1 (at 0.5 A cm-2) and 0.136 mV h-1 (at 1.0 A cm-2) over 500 h. This research overcomes the traditional trade-off between activity and durability, indicating that PS can be widely applied across various energy fields, including electrochemical storage and conversion.

Enhanced Hydrogen Evolution Reaction in Alkaline Media via Ruthenium-Chromium Atomic Pairs Modified Ruthenium Nanoparticles

Precisely optimizing the electronic metal support interaction (EMSI) of the electrocatalysts and tuning the electronic structures of active sites are crucial for accelerating water adsorption and dissociation kinetics in alkaline hydrogen evolution reaction (HER). Herein, an effective strategy is applied to modify the electronic structure of Ru nanoparticles (RuNPs) by incorporating Ru single atoms (RuSAs) and Ru and Cr atomic pairs (RuCrAPs) onto a nitrogen-doped carbon (N-C) support through optimized EMSI. The resulting catalyst, RuNPs-RuCrAPs-N-C, shows exceptional performance for alkaline HER, achieving a six times higher turnover frequency (TOF) of 13.15 s⁻¹ at an overpotential of 100 mV, compared to that of commercial Pt/C (2.07 s⁻¹). Additionally, the catalyst operates at a lower overpotential at a current density of 10 mA·cm⁻2 (η10 = 31 mV), outperforming commercial Pt/C (η10 = 34 mV). Experimental results confirm that the RuCrAPs modified RuNPs are the main active sites for the alkaline HER, facilitating the rate-determining steps of water adsorption and dissociation. Moreover, the Ru-Cr interaction also plays a vital role in modulating hydrogen desorption. This study presents a synergistic approach by rationally combining single atoms, atomic pairs, and nanoparticles with optimized EMSI effects to advance the development of efficient electrocatalysts for alkaline HER.

Pt/α-MoC Catalyst Boosting pH-Universal Hydrogen Evolution Reaction at High Current Densities

Constructing subnanometric electrocatalysts is an efficient method to synergistically accelerate H2O dissociation and H+ reduction for pH-universal hydrogen evolution reaction (HER) for industrial water electrolysis to produce green hydrogen. Here, we construct a subnanometric Pt/α-MoC catalyst, where the α-MoC component can dissociate water effectively, with the rapid proton release kinetics of Pt species on Pt/α-MoC to obtain a good HER performance at high current densities in all-pH electrolytes. Quasi-in situ X-ray photoelectron spectroscopy analyses and density functional theory calculations confirm the highly efficient water dissociation capability of α-MoC and the thermodynamically favorable desorption process of hydrolytically dissociated protons on Pt sites at the high current density. Consequently, Pt/α-MoC requires only a low overpotential of 125 mV to achieve a current density of 1000 mA cm-2. Moreover, a Pt/α-MoC-based proton exchange membrane water electrolysis device exhibits a low cell voltage (1.65 V) and promising stability over 300 h with no performance degradation at an industrial-level current density of 1 A cm-2. Notably, even at a current of 100 A, the cell voltage remains low at 2.15 V, demonstrating Pt/α-MoC's promising potential as a scalable alternative for industrial hydrogen production. These findings elucidate the synergistic mechanism of α-MoC and atomically dispersed Pt in promoting efficient HER, offering valuable guidance for the design of electrocatalysts in high current density hydrogen.

Cascade Reaction Enables Heterointerfaces-Enriched Nanoarrays for Ampere-Level Hydrogen Production

Designing high-performance electrocatalysts with superior catalytic activity and stability is essential for large-scale hydrogen production via water electrolysis. Heterostructure nanoarrays are promising candidates, though achieving both high activity and stability simultaneously, especially under high current densities, remains challenging. To this end, we have developed a cascade reaction process that constructs a series of heterostructure nanoarrays with rich heterointerfaces. This process involves treating nickel foam (NF) with molten KSCN and transition metal salts. Initially, NF reacts with KSCN to form Ni9S8 nanoarrays and S2- ions, which are subsequently captured by transition metal ions to form sulfides that are directly integrated onto the nanoarrays, resulting in abundant heterointerfaces. Both experimental and theoretical results indicate that these rich heterointerfaces significantly enhance the interfacial interaction between Ni9S8 and RuS2 within the nanoarrays (termed RH-Ni9S8/RuS2), markedly improving both the intrinsic activity and stability for the hydrogen evolution reaction (HER). Impressively, the RH-Ni9S8/RuS2 demonstrates exceptional HER performance, achieving a low overpotential of just 180 mV at 1000 mA cm-2 and maintaining stability for up to 500 h under such high-current-density conditions. This innovative approach paves the way for the interfacial design and synthesis of high-performance catalysts for ampere-level hydrogen production.

Tuning the electronic-state of metal cobalt/cobalt iron alloy hetero-interface embedded in nitrogen-doped carbon nanotube arrays for boosting electrocatalytic overall water splitting

Maximizing the utilization of active sites and tuning the electronic-state are crucial yet extremely challenging in enhancing the ability of alloy-based catalysts to catalyze hydrogen and oxygen evolution reactions (HER and OER). Here, the 3D self-supported N-doped carbon nanotube arrays (NCNTAs) was synthesized on Ni foam by the drop-casting and calcination method, where the metal Co and Co7Fe3 alloy were enclosed at the NCNT tip (denoted as Co/Co7Fe3@NCNT/NF). The Co/Co7Fe3 hetero-interface formation led to changes in the electronic state, which can optimize the adsorption free energy of reaction intermediates and thereby boost the intrinsic catalytic performance. The well-dispersed carbon nanotube arrays with superhydrophilic and superaerophobic characteristic promotes electrolyte permeation and bubbles escape. Therefore, the optimized Co/Co7Fe3-10@NCNT/NF exhibits superior bifunctional activities with overpotential of 93 and 174 mV at 10 mA cm-2 for HER and OER, respectively. For overall water splitting (OWS), the assembled dual electrode device with Co/Co7Fe3-10@NCNT/NF only requires a low voltage of 1.56 V to achieve 10 mA cm-2 and stabilizes for 24 h at 100 mA cm-2. The result underscores the importance of hetero-interface electronic effect and carbon nanotube arrays in catalytic water splitting, providing valuable insights for the design of more advanced bifunctional electrocatalysts for OWS.

Dual-bioinspired Janus mesh membrane with controllable bubbles manipulation property for efficient water splitting and pure gas collection

Water splitting, as a promising clean energy source, has garnered significant attention owing to the escalating global energy crisis. However, prior research has largely focused on electrode materials rather than bubble manipulation, which plays a crucial role in the process. Although using the previously published "Releasing strategy" effectively eliminates micro-sized bubbles from the electrode material for efficient water splitting, the released tiny-sized bubbles pose challenges for controllable and pure collection. Herein, a new "Managing strategy", integrating the "Transporting strategy" for rapid directional bubble transport with the "Collecting strategy" for controllable bubble collection, aiming to develop smart integrated water-splitting devices for efficient continuous water splitting and pure gas collection. This advanced functional electrode, designed with a lotus leaf-inspired Janus wettability interface for timely directional bubble transport and a water-spider hair structure-inspired aerophilic surface for efficient bubble collection, enables pure, efficient, and continuous water splitting. It achieves this by releasing gas products of controllable larger sizes, collecting them at a faster rate, and reducing the probability of H2/O2 collisions. Beyond enabling water splitting, this approach is also applicable to other gas-involving applications.

RuCo@C Hollow Nanoprisms Derived from ZIF-67 for Enhanced Hydrogen and Oxygen Evolution Reactions

Zeolitic imidazolate frameworks (ZIFs) are commonly used to create complex hollow structures for energy applications. This study presents a simple method to produce a novel hollow nanoprism Co@C hierarchical composite from ZIF-67 through high-temperature treatment at 800 °C. This composite serves as a platform for Ru nanoparticle deposition, forming RuCo@C hollow nanoprism (RuCo@C HNP). As an electrocatalyst in 1 M KOH, RuCo@C HNP exhibits excellent hydrogen evolution reaction (HER) performance, with a low overpotential of 32 mV to reach 10 mA cm-2, a Tafel slope of 39.67 mV dec-1, a high turnover frequency (TOF) of 3.83 s-1 at η200, and stable performance over 50 h. It also achieves a low η10 of 266 mV for the oxygen evolution reaction (OER) with a Tafel slope of 45.22 mV dec-1. Density functional theory (DFT) calculations reveal that Ru doping in Ni/Co maintains a low water dissociation barrier, reduces the energy barrier for the OER rate-determining step, and creates active sites for H*, enhancing adsorption/desorption abilities. These results are attributed to the synergy between Co and Ru and the hollow prism structure's increased surface area. This method for synthesizing hollow structures using ZIF composites shows promise for applications in the energy sector.

Dynamic regulation of ferroelectric polarization using external stimuli for efficient water splitting and beyond

Establishing and regulating the ferroelectric polarization in ferroelectric nano-scale catalysts has been recognized as an emerging strategy to advance water splitting reactions, with the merits of improved surface charge density, high charge transfer rate, increased electronic conductivity, the creation of real active sites, and optimizing the chemisorption energy. As a result, engineering and tailoring the ferroelectric polarization induced internal electric field provides significant opportunities to improve the surface and electronic characteristics of catalysts, thereby enhancing the water splitting reaction kinetics. In this review, an interdisciplinary and comprehensive summary of recent advancements in the construction, characterization, engineering and regulation of the polarization in ferroelectric-based catalysts for water splitting is provided, by exploiting a variety of external stimuli. This review begins with a detailed overview of the classification, benefits, and identification methodologies of the ferroelectric polarization induced internal electric field; this offers significant insights for an in-depth analysis of ferroelectric-based catalysts. Subsequently, we explore the underlying structure-activity relationships for regulating the ferroelectric polarization using a range of external stimuli which include mechanical, magnetic, and thermal fields to achieve efficient water splitting, along with a combination of two or more fields. The review then highlights emerging strategies for multi-scale design and theoretical prediction of the relevant factors to develop highly promising ferroelectric catalysts for efficient water splitting. Finally, we present the challenges and perspectives on the potential research avenues in this fascinating and new field. This review therefore delivers an in-depth examination of the strategies to engineer the ferroelectric polarization for the next-generation of water electrolysis devices, systems and beyond.

Enhanced Water Splitting with Sulfur-Doped Nickel Ferrite for Green Hydrogen at Industrial Current Density

The main challenge for water electrolysis is that continuous and effective hydrogen evolution at high current densities is unattainable due to the quick degradation of performance that occurs with extended large-current operation. In this work, sulfur-doped nickel ferrite nanocomposites were prepared using simple hydrothermal method with the objective of improving electrocatalytic green hydrogen production at industrial current densities. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to analyse the crystalline structure, morphology, and chemical composition of the synthesised nanocomposites. The prepared S-NiFe2O4/NF (NS-85) catalyst exhibits excellent electrochemical water-splitting activity, a low overpotential, a high current density, and extended stability lasting more than 12 hours. The NS-85/NF electrode has a cathodic current density of 300 mA cm-2 at -0.329 V overpotential and at the lowest overpotential of -0.264 V, the electrode has a current density of 100 mA cm-2. Our work provides new approaches to the development of earth-abundant, stable, scalable, and highly effective catalysts for industrial water electrolysis.

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

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

Rational design of precatalysts and controlled evolution of catalyst-electrolyte interface for efficient hydrogen production

The concept of precatalyst is widely accepted in electrochemical water splitting, but the role of precatalyst activation and the resulted changes of electrolyte composition is often overlooked. Here, we elucidate the impact of potential-dependent changes for both precatalyst and electrolyte using Co2Mo3O8 as a model system. Potential-dependent reconstruction of Co2Mo3O8 precatalyst results in an electrochemically stable Co(OH)2@Co2Mo3O8 catalyst and additional Mo dissolved as MoO42- into electrolyte. The Co(OH)2/Co2Mo3O8 interface accelerates the Volmer reaction and negative potentials induced Mo2O72- (from MoO42-) further enhances proton adsorption and H2 desorption. Leveraging these insights, the well-designed MoO42-/Mo2O72- modified Co(OH)2@Co2Mo3O8 catalyst achieves a Faradaic efficiency of 99.9% and a yield of 1.85 mol h-1 at -0.4 V versus reversible hydrogen electrode (RHE) for hydrogen generation. Moreover, it maintains stable over one month at approximately 100 mA cm-2, highlighting its industrial suitability. This work underscores the significance of understanding on precatalyst reconstruction and electrolyte evolution in catalyst design.

Synergizing superwetting and architected electrodes for high-rate water splitting

Water splitting is one of the most promising technologies for generating green hydrogen. To meet industrial demand, it is essential to boost the operation current density to industrial levels, typically in the hundreds of mA cm-2. However, operating at these high current densities presents significant challenges, with bubble formation being one of the most critical issues. Efficient bubble management is crucial as it directly impacts the performance and stability of the water splitting process. Superwetting electrodes, which can enhance aerophobicity, are particularly favorable for facilitating bubble detachment and transport. By reducing bubble contact time and minimizing the size of detached bubbles, these electrodes help prevent blockage and maintain high catalytic efficiency. In this review, we aim to provide an overview of recent advancements in tackling bubble-related issues through the design and implementation of superwetting electrodes, including surface modification techniques and structural optimizations. We will also share our insights into the principles and mechanisms behind the design of superwetting electrodes, highlighting the key factors that influence their performance. Our review aims to guide future research directions and provides a solid foundation for developing more efficient and durable superwetting electrodes for high-rate water splitting.

Efficient Methanol Oxidation Kinetics Enabled by an Ordered Heterocatalyst with Dual Electric Fields

Induced by a sharp-tip-enhanced electric field, periodical nanoassemblies can regulate the reactant flux on the electrode surface, efficiently optimizing the mass transfer kinetics in electrocatalysis. However, when the nanoscale building blocks in homoassemblies are arranged densely, it results in the overlap and reduction of the local electric field. Herein, we present a comprehensive kinetic heteromodel that simultaneously couples the sharp-tip-enhanced electric field and charge transfer electric field between different building blocks with any arrangement densities. The dual electric fields drive the diffusion of reactants from the bulk solution to the electrode surface, significantly enhancing mass transfer kinetics along the horizontal and longitudinal directions, which promotes the electrocatalytic activity significantly. Moreover, the wide generality of the model is further confirmed by electrochemical experiments involving various electrocatalytic systems and catalysts. Therefore, this work highlights the significant role of dual electric fields in electrocatalysis, which is expected to facilitate the development of customized and outstanding catalysts in the future.

Guanine-Assisted Contrived Low Pt-Integrated Mo2C/C for Hydrogen Evolution Reaction

Due to the high cost of the available Pt electrocatalysts, the large-scale water electrolysis production of hydrogen has been hindered. Hydrogen generation via electrochemical water splitting is a renewable energy essential to a sustainable society, creating a distinct material interface that shows Pt-like properties with long-term stability crucial to hydrogen evolution reactions (HERs). Here, we synthesized the guanine-assisted facile synthesis of 1 wt % Pt/Mo2C/C having a layered type morphology via solid state calcined process followed by chemical reduction. The well-developed 1 wt % Pt/Mo2C/C heterostructure is analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to understand the percentage of Pt doped on Mo2C/C. The as-synthesized 1 wt % Pt/Mo2C/C heterostructure exhibits a better HER activity than a commercial Pt/C with a small overpotential of 19 mV to reach a current density at 10 mA cm-2 with a Tafel slope of 28 mV/dec. The catalyst 1 wt % Pt/Mo2C/C shows a long-term stability of 42 h in 0.5 M H2SO4. The layered sheet structure with the N-doped carbon (C) nanosheet, encapsulating well-dispersed Pt within the layers, significantly enhances the reaction kinetics of the 1 wt % Pt/Mo2C/C. This design creates a synergistic effect among Mo2C, Pt, and the carbon matrix, improving catalytic performance. Theoretical calculations using the density functional theory (DFT) indicate the active sites for hydrogen evolution on Pt-integrated Mo2C/C. The 1 wt % Pt/Mo2C/C possessed a significantly reduced ΔGH* value (-0.06 eV) as compared to the pristine Mo2C/C material (ΔGH* = 0.34 eV), suggesting a higher catalytic activity. This simple method offers a fresh means to make clearly defined carbides and sheds light on creating low-Pt catalysts for a scalable HER.

Efficient Nitrate to Ammonia Conversion on Bifunctional IrCu4 Alloy Nanoparticles

Electrochemical nitrate reduction (NO3RR) to ammonia presents a promising alternative strategy to the traditional Haber-Bosch process. However, the competitive hydrogen evolution reaction (HER) reduces the Faradaic efficiency toward ammonia, while the oxygen evolution reaction (OER) increases the energy consumption. This study designs IrCu4 alloy nanoparticles as a bifunctional catalyst to achieve efficient NO3RR and OER while suppressing the unwanted HER. This is achieved by operating the NO3RR at positive potentials using the IrCu4 catalyst, which allows a Faradaic efficiency of 93.6% for NO3RR. When applied to OER catalysis, the IrCu4 alloy also shows excellent results, with a relatively low overpotential of 260 mV at 10 mA cm-2. Stable ammonia production can be achieved for 50 h in a 16 cm2 flow electrolyzer in simulated working conditions. Our research provides a pathway for optimizing NO3RR through bifunctional catalysts in a tandem approach.

Separating nanobubble nucleation for transfer-resistance-free electrocatalysis

Electrocatalytic gas-evolving reactions often result in bubble-covered surfaces, impeding the mass transfer to active sites. Such an issue will be worsened in practical high-current-density conditions and can cause sudden cell failure. Herein, we develop an on-chip microcell-based total-internal-reflection-fluorescence-microscopy to enable operando imaging of bubbles at sub-50 nm and dynamic probing of their nucleation during hydrogen evolution reaction. Using platinum-interfacial metal layer-graphene as model systems, we demonstrate that the strong binding energy between interfacial metal layer and graphene-evidenced by a reduced metal-support distance and enhanced charge transfer-facilitates hydrogen spillover from platinum to the graphene support due to lower energy barriers compared to the platinum-graphene system. This results in the spatial separation of bubble nucleation from the platinum surface, notably enhancing catalytic activity, as demonstrated in both microcell and polymer electrolyte membrane cell experiments. Our findings offer insights into bubble nucleation control and the design of electrocatalytic interfaces with minimized transfer resistance.

Oxyanions Enhancing Crystallinity of Reconstructed Phase for Oxygen Evolution Reaction

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

A Chalcogenide-Derived NiFe2O4 as Highly Efficient and Stable Anode for Anion Exchange Membrane Water Electrolysis

Developing low-cost, highly active, and durable oxygen evolution reaction (OER) electrodes is one of the critical scientific issues for anion exchange membrane water electrolyzer (AEM-WE). Herein, we report a vacancy-rich and alkali-stable NiFe2O4-type electrode (named as NiFeOx-350-Ov), derived from the chemical-vapor deposited precursor NiFeSexSy-350, as an efficient and robust anode material. The obtained electrode affords current densities of 100 and 500 mA cm-2 at overpotentials of 245 and 270 mV, respectively, and displays excellent long-term durability sustaining 1.0 A cm-2 at least for 1000 h. When coupled with Ni4Mo/MoO2/NF as a hydrogen evolution reaction (HER) catalyst, the resulting platinum-group metal (PGM)-free single-cell AEM-WE exhibits a cell voltage of 1.71 V at the current density of 1000 mA cm-2 at 80 °C and long-term durability during a current-cycling test between 0.5 A cm-2 and 1.0 A cm-2 over 150 h at 60 °C. This work highlights a unique reconstruction strategy for preparing highly active and durable OER catalysts used in PGM-free AEM-WE.

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.

Fabrication of Ru-doped CuMnBP micro cluster electrocatalyst with high efficiency and stability for electrochemical water splitting application at the industrial-level current density

Electrochemical water splitting has been considered as a key pathway to generate environmentally friendly green hydrogen energy and it is essential to design highly efficient electrocatalysts at affordable cost to facilitate the redox reactions of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, a novel micro-clustered Ru/CuMnBP electrocatalyst is introduced, prepared via hydrothermal deposition and soaking-assisted Ru doping approaches on Ni foam substrate. Ru/CuMnBP micro-clusters exhibit relatively low HER/OER turnover overpotentials of 11 mV and 85 mV at 10 mA/cm2 in 1 M KOH. It also demonstrates a low 2-E turnover cell voltage of 1.53 V at 10 mA/cm2 for the overall water-splitting, which is comparable with the benchmark electrodes of Pt/C||RuO2. At a super high-current density of 2000 mA/cm2, the dual functional Ru/CuMnBP demonstrates an exceptionally low 2-E cell voltage of 3.13 V and also exhibits superior stability for over 10 h in 1 M KOH. Excellent electrochemical performances originate from the large electrochemical active surface area with the micro cluster morphology, high intrinsic activity of CuMnBP micro-clusters optimized through component ratio adjustment and the beneficial Ru doping effect, which enhances active site density, conductivity and stability. The usage of Ru in small quantities via the simple soaking doping approach significantly improves electrochemical reaction rates for both HER and OER, making Ru/CuMnBP micro-clusters promising candidates for advanced electrocatalytic applications.