Superaerophobic Electrode with Metal@Metal‐Oxide Powder Catalyst for Oxygen Evolution Reaction

A stable and highly active oxygen evolution reaction (OER) electrode is the key for fast and robust O₂ production, which is one of the essential points for various kinds of energy conversion systems, such as water splitting, lithium‐O₂ battery and artificial photosynthesis. Here, superaerophobic electrodes with metal@metal‐oxide powder catalysts are shown, which demonstrate high and stable OER activity. The active‐site‐density of metal@metal‐oxide catalysts is increased over one order of magnitude than those of pure metal oxides due to the large enhancement of electrical conductivity, revealing the substantial enhancement of electrochemical OER kinetics. Furthermore, the superaerophobic property of electrodes is favorable for fast O₂ desorption, which improves electrochemical active surface area (EASA) during OER. The superaerophobic electrode with metal@metal‐oxide powder catalysts provides the new insight for increase of active‐site‐density and EASA simultaneously, which are the key factors to determine the activity of OER electrode.     

Phosphorous‐Doped Graphite Layers with Outstanding Electrocatalytic Activities for the Oxygen and Hydrogen Evolution Reactions in Water Electrolysis

Advances demonstrate that the incorporation of phosphorous into the network of nitrogen, sulfur, or fluorine‐doped carbon materials can remarkably enhance their oxygen and hydrogen evolution activities. However, the electrocatalytic behaviors of pristine phosphorous single‐doped carbon catalysts toward the oxygen and hydrogen evolution reactions (OER and HER) are rarely investigated and their corresponding active species are not yet explored. To clearly ascertain the effects of phosphorous doping on the OER and HER and identify the active sites, herein, phosphorous unitary‐doped graphite layers with different phosphorous species distributions are prepared and the correlations between the oxygen or hydrogen evolution activity and different phosphorous species are investigated, respectively. Results indicate that phosphorous single‐doped graphite layers show a superior oxygen evolution activity to most of the reported OER catalysts and the commercial IrO₂ in alkaline medium, and comparable hydrogen evolution activity to most reported carbon catalysts in acidic medium. Moreover, the relevancies unveil that the C? O? P species are the main OER active species, and the defects derived from the decomposition of C₃? P = O species are the main active sites for HER, as evidenced by density functional theory calculations, showing a new perspective for the design of more effective phosphorous‐containing water‐splitting catalysts.     

Mesh‐on‐Mesh Graphitic‐C3N4@Graphene for Highly Efficient Hydrogen Evolution

Mesoporous materials have attracted considerable interest due to their huge surface areas and numerous active sites that can be effectively exploited in catalysis. Here, 2D mesoporous graphitic‐C₃N₄ nanolayers are rationally assembled on 2D mesoporous graphene sheets (g‐CN@G MMs) by in situ selective growth. Benefiting from an abundance of exposed edges and rich defects, fast electron transport, and a multipathway of charge and mass transport from a continuous interconnected mesh network, the mesh‐on‐mesh g‐CN@G MMs hybrid exhibits higher catalytic hydrogen evolution activity and stronger durability than most of the reported nonmetal catalysts and some metal‐based catalysts.     

A Self‐Standing High‐Performance Hydrogen Evolution Electrode with Nanostructured NiCo2O4/CuS Heterostructures

An efficient self‐standing 3D hydrogen evolution cathode has been developed by coating nickel cobaltite (NiCo₂O₄)/CuS nanowire heterostructures on a carbon fiber paper (CFP). The obtained CFP/NiCo₂O₄/CuS electrode shows exceptional hydrogen evolution reaction (HER) performance and excellent durability in acidic conditions. Remarkably, as an integrated 3D hydrogen‐evolving cathode operating in acidic electrolytes, CFP/NiCo₂O₄/CuS maintains its activity more than 50 h and exhibits an onset overpotential of 31.1 mV, an exchange current density of 0.246 mA cm^?2, and a Tafel slope of 41 mV dec^?1. Compared to other non‐Pt electrocatalysts reported to date, CFP/NiCo₂O₄/CuS exhibits the highest HER activity and can be used in HER to produce H₂ with nearly quantitative faradaic yield in acidic aqueous media with stable activity. Furthermore, by using CFP/NiCo₂O₄/CuS as a self‐standing electrode in a water electrolyzer, a current density of 18 mA cm^?2 can be achieved at a voltage of 1.5 V which can be driven by a single‐cell battery. This strategy provides an effective, durable, and non‐Pt electrode for water splitting and hydrogen generation.     

NiMo Solid Solution Nanowire Array Electrodes for Highly Efficient Hydrogen Evolution Reaction

Developing high‐performance noble metal–free electrodes for efficient water electrolysis for hydrogen production is of paramount importance for future renewable energy resources. However, a grand challenge is to tailor the factors affecting the catalytic electrodes such as morphology, structure, and composition of nonprecious metals. Alloying catalytic metals can lead to a synergistic effect for superior electrocatalytic properties. However, alloy formation in solution at low synthesis temperatures may result in better catalytic properties as compared to those at high temperatures due to the controlled reaction kinetics of nucleation and growth mechanisms. Herein, an aqueous solution–based preparation technology is developed to produce NiMo alloy nanowire arrays. The NiMo alloy shows significantly improved hydrogen evolution reaction (HER) catalytic activity, featured with extremely low overpotentials of 17 and 98 mV at 10 and 400 mA cm^?2, respectively, in an alkaline medium, which are better than most state‐of‐the‐art non‐noble metal–based catalysts and even comparable to platinum‐based electrodes. Analyses indicate that the lattice distortions induced by Mo incorporation, increased interfacial activity by alloy formation, and plenty of MoNi₄ active sites at nanowires surface collectively contribute to remarkably enhanced catalytic activity. This study provides a powerful toolbox for highly efficient nonprecious metal–based electrodes for practical HER application.     

Water‐Soluble Conjugated Molecule for Solar‐Driven Hydrogen Evolution from Salt Water

Photocatalytic hydrogen evolution is an attractive method for the acquisition of clean and sustainable energy with the use of solar power. Most reported studies have been carried out in scarce pure water. Therefore, the development of an artificial photosynthesis system that works perfectly with the earth's abundant seawater would be attractive. Herein, a supramolecular strategy for photocatalytic hydrogen production from the simulated seawater under sunlight irradiation (AM 1.5G, 100 mW cm^?2) is presented using a water‐soluble, conjugated molecule as the photosensitizer and the photodeposited Pt nanoparticles as the catalyst. Inspired by the natural photosynthesis system, unprecedented advantage of the chloride ions in seawater is taken and the formation of supramolecular structure is promoted by electrostatic interactions between chloride ions and the fine‐designed PorFN, which further facilitates the loading of Pt nanoparticles and multielectron transfer. As a result, a hydrogen evolution rate of 10.8 mmol h^?1 g^?1 is achieved in the simulated seawater. Moreover, the photocatalytic activity shows relatively low dependence on the light intensity, which is of great importance for practical applications.     

RhMoS2 Nanocomposite Catalysts with Pt‐Like Activity for Hydrogen Evolution Reaction

High overpotentials and low efficiency are two main factors that restrict the practical application for MoS₂, the most promising candidate for hydrogen evolution catalysis. Here, Rh?MoS₂ nanocomposites, the addition of a small amount of Rh (5.2 wt%), exhibit the superior electrochemical hydrogen evolution performance with low overpotentials, small Tafel slope (24 mV dec^?1), and long term of stability. Experimental results reveal that 5.2 wt% Rh?MoS₂ nanocomposite, even exceeding the commercial 20 wt% Pt/C when the potential is less than ?0.18 V, exhibits an excellent mass activity of 13.87 A mg_metal^?1 at ?0.25 V, four times as large as that of the commercial 20 wt% Pt/C catalyst. The hydrogen yield of 5.2 wt% Rh?MoS₂ nanocomposite is 26.3% larger than that of the commercial 20 wt% Pt/C at the potential of ?0.25 V. The dramatically improved electrocatalytic performance of Rh?MoS₂ nanocomposites may be attributed to the hydrogen spillover from Rh to MoS₂.     

Reversed Spillover Effect Activated by Pt Atom Dimers Boosts Alkaline Hydrogen Evolution Reaction

The hydrogen spillover effect has garnered considerable attention as a promising avenue to enhance the activity of the hydrogen evolution reaction (HER) in metal-support compound materials. Herein, Pt atom dimers on the NiOOH support are successfully synthesized with a reversed hydrogen spillover effect, demonstrating much better alkaline HER activity than Pt single atoms and Pt clusters. Atomic and electronic structure characterizations unequivocally verify the anchoring of Pt atom dimers on NiOOH through Pt─O bonds, thus obtaining a reversed and enhanced hydrogen spillover effect. Theoretical and experimental results indicate that NiOOH exhibits pronounced water dissociation capability, while the Pt atom dimers, in comparison to Pt single atoms and Pt clusters, demonstrate superior hydrogen desorption ability. The reversed spillover with Pt atom dimers leads to remarkable HER activity in alkaline solutions, as evidenced by an ultra-small overpotential of 13 mV at 10 mA cm⁻². These findings not only provide insights into the potential use of atom dimers for HER, but also shed light on reversed spillover in designing high-performance catalysts.     

Molybdenum Phosphide/Carbon Nanotube Hybrids as pH‐Universal Electrocatalysts for Hydrogen Evolution Reaction

Molybdenum phosphide (MoP) has received increasing attention due to its high catalytic activity in hydrogen evolution reaction (HER). However, it remains difficult to construct well‐defined MoP nanostructures with large density of active sites and high intrinsic activity. Here, a facile and general method is reported to synthesize an MoP/carbon nanotube (CNT) hybrid featuring small‐sized and well‐crystallized MoP nanoparticles uniformly coated on the sidewalls of multiwalled CNT. The MoP/CNT hybrid exhibits impressive HER activities in pH‐universal electrolytes, and requires the overpotentials as low as 83, 102, and 86 mV to achieve a cathodic current density of 10 mA cm^?2 in acidic 0.5 m H₂SO₄, neutral 1 m phosphate buffer solution, and alkaline 1 m KOH electrolytes, respectively. It is found that the crystallinity of MoP has significant influence on HER activity. This study provides a new design strategy to construct MoP nanostructures for optimizing its catalytic performance.     

高析氢活性Ni-Mo-Zn合金电极的制备与表征

采用两步电沉积方法在碱性柠檬酸盐-氨水络合体系中制备了含有Ni-Mo中间层的Ni-Mo-Zn电极,通过在热碱溶液中浸泡除去部分Zn后得到高析氢活性电极.SEM测试发现,该电极的合金镀层表面有多层结构和二级颗粒,它们经热碱溶液浸泡后会形成大颗粒包裹小颗粒(粒径小于1μm)的类似"藤壶"状表面形貌.通过稳态阴极极化曲线考察了不同电极的催化析氢性能,发现含有Ni-Mo中间镀层的Ni-Mo-Zn电极在碱洗后较Ni电极和没有中间层的Ni-Mo-Zn电极具有更高的析氢活性.在0.1 A·cm-2电流密度下,析氢反应极化电位分别比Ni电极和没有中间层的Ni-Mo-Zn电极正移502 mV和93 mV,交换电流密度分别是Ni电极和Ni-Mo-zn电极的91倍和4倍.该电极的高活性主要归因于镀层的特殊表面结构和Ni-Mo中间镀层的存在.     

Rh?MoS2 Nanocomposite Catalysts with Pt‐Like Activity for Hydrogen Evolution Reaction

High overpotentials and low efficiency are two main factors that restrict the practical application for MoS₂, the most promising candidate for hydrogen evolution catalysis. Here, Rh? MoS₂ nanocomposites, the addition of a small amount of Rh (5.2 wt%), exhibit the superior electrochemical hydrogen evolution performance with low overpotentials, small Tafel slope (24 mV dec^?1), and long term of stability. Experimental results reveal that 5.2 wt% Rh? MoS₂ nanocomposite, even exceeding the commercial 20 wt% Pt/C when the potential is less than ?0.18 V, exhibits an excellent mass activity of 13.87 A mg_metal^?1 at ?0.25 V, four times as large as that of the commercial 20 wt% Pt/C catalyst. The hydrogen yield of 5.2 wt% Rh? MoS₂ nanocomposite is 26.3% larger than that of the commercial 20 wt% Pt/C at the potential of ?0.25 V. The dramatically improved electrocatalytic performance of Rh? MoS₂ nanocomposites may be attributed to the hydrogen spillover from Rh to MoS₂.     

Structure-Induced Stability in Sinuous Black Silicon for Enhanced Hydrogen Evolution Reaction Performance

Clean energy infrastructures of the future depend on efficient, low-cost, long-lasting systems for the conversion and storage of solar energy. This is currently limited by the durability and economic viability of today's solar energy systems. These limitations arise from a variety of technical challenges; primarily, a need remains for the development of stable solar absorber–catalyst interfaces and improved understanding of their mechanisms. Although thin film oxides formed via atomic layer deposition have been widely employed between the solar absorber–catalyst interfaces to improve the stability of photoelectrochemical devices, few stabilization strategies have focused on improving the intrinsic durability of the semiconductor. Here, a sinuous black silicon photocathode (s-bSi) with intrinsically improved stability owing to the twisted nanostructure is demonstrated. Unlike columnar black silicon with rapidly decaying photocurrent density, s-bSi shows profound stability in strong acid, neutral, and harsh alkaline conditions during a 24-h electrolysis. Furthermore, scanning transmission electron microscopy studies prior to and post electrolysis demonstrate limited silicon oxide growth inside the walls of s-bSi. To the authors’ knowledge, this is the first time structure-induced stability has been reported for enhancing the stability of a photoelectrode/catalyst interface for solar energy conversion.     

Ordered Mesoporous Metastable α‐MoC1−x with Enhanced Water Dissociation Capability for Boosting Alkaline Hydrogen Evolution Activity

The sluggish reaction kinetics of the alkaline hydrogen evolution reaction (HER) remains an important challenge for water–alkali electrolyzers, which originates predominantly from the additional water dissociation step required for the alkaline HER. In this work, it is demonstrated theoretically and experimentally that metastable, face‐centered‐cubic α‐MoC_1?x phase shows superior water dissociation capability and alkaline HER activity than stable, hexagonal‐close‐packed Mo₂C phase. Next, high surface area ordered mesoporous α‐MoC_1?x (MMC) is designed via a nanocasting method. In MMC structure, the α‐MoC_1?x phase facilitates the water dissociation reaction, while the mesoporous structure with high surface area enables a high dispersion of metal NPs and efficient mass transport. As a result, Pt nanoparticles (NPs) supported on MMC (Pt/MMC) show substantially enhanced alkaline HER activity in terms of overpotentials, Tafel slopes, mass and specific activities, and exchange current densities, compared to commercial Pt/C and Pt NPs supported on particulate α‐MoC_1?x or β‐Mo₂C. Notably, Pt/MMC shows very low Tafel slope of 30 mV dec^–1, which is the lowest value among the reported Pt‐based alkaline HER catalysts, suggesting the critical role of MMC in enhancing the HER kinetics. The promotional effect of MMC support in the alkaline HER is further demonstrated with an Ir/MMC catalyst.     

Atomic-Scale Configuration Enables Fast Hydrogen Migration for Electrocatalysis of Acidic Hydrogen Evolution

The efficiency of hydrogen evolution reaction (HER) electrocatalysts under acidic conditions is largely determined by the equilibrium of hydrogen adsorption/desorption on the catalyst surface. A promising strategy for enhancing the performance of multimetal-supported HER electrocatalysts is the utilization of hydrogen spillover. However, current heterostructured catalysts often present challenges such as high interfacial transport barriers, extended reaction paths, and intricate synthesis processes. Addressing these limitations, a novel orthorhombic SrHf_1−xRu_xO_3−δ perovskite oxide is proposed as an exemplary model for an atomic-level configuration design strategy. This material exhibits a unique synergistic effect of multiple atomic-level catalytic sites between Hf/Ru pairs, overcoming the aforementioned challenges. This study presents a new cooperative mechanism for HER, consisting of three steps: proton adsorption on the Hf site, hydrogen migration via a strong O-bridge site, and H₂ detachment from the Ru active site. The high conductivity and unusual charge redistribution within the Hf-O-Ru structure further enhance the specific acidic HER activity of SrHf_1−xRu_xO_3−δ. This research paves the way for designing high-performance HER catalysts for acidic media, leveraging hydrogen spillover and atomic-scale configurations. The findings have significant implications for the development of efficient, cost-effective, and environmentally friendly hydrogen production technologies.     

Bifunctional Electrode Design Targeting Co-Enhanced Kinetics and Mass Transport for Hydrogen and Water Oxidation Reactions

Bifunctional catalysts based on noble metals have achieved practical-level performances in round-trip energy conversion systems. However, the required amount of noble metals should be substantially reduced via a new catalyst design that can pursue the synergy of the constituent materials’ intrinsic properties and architectural maneuver over reactant/product transport. In this study, cross-stacked Ir and Pt nanowires resolved the bottlenecks of two reactions essential for the hydrogen-based energy system: i) hydrogen spillover phenomenon between Pt and Ir nanowires to expedite the hydrogen oxidation reaction and ii) spacing Ir nanowires sufficiently to enhance the mass transport of the oxygen evolution reaction. Simultaneously accommodating the different strategies within the single catalyst layer, a new horizon to design a bifunctional electrode is proposed with the high performance of polymer electrolyte membrane unitized regenerative fuel cells: 47% of round-trip efficiency at 0.5 A cm⁻² with total noble metal loading < 0.3 mg cm⁻².     

Embedding RhPx in N,P Co‐Doped Carbon Nanoshells Through Synergetic Phosphorization and Pyrolysis for Efficient Hydrogen Evolution

Rational design and controllable synthesis of well‐defined nanostructures with high stability and Pt‐like activity for hydrogen evolution reaction (HER) are critical for renewable energy conversion. Herein, a unique pyrolysis strategy is demonstrated for the synthesis of RhP_x nanoparticles (NPs) in N, P co‐doped thin carbon nanoshells (RhP_x@NPC nanoshells) that display high electrocatalytic activity and stability over a wide pH range. This strategy involves simultaneous phosphorization and pyrolysis processes that can produce highly‐dispersed RhP_x NPs within N, P co‐doped carbon nanoshells and at the same time induce thinning of carbon nanoshells from inside out. The resulting RhP_x@NPC nanoshells not only possess Pt‐like activity for HER with low overpotentials to achieve 10 mA cm^?2 (22 mV in 0.5 m H₂SO₄, 69 mV in 1.0 m KOH, and 38 mV in 1.0 m phosphate buffered saline (PBS)) but also provide long‐term durability in a wide pH range. The remarkable HER performance of RhP_x@NPC nanoshells is ascribed to the high surface area, abundant mesoporosity, strong catalyst–support interaction, ultrathin carbon encapsulation, and N, P co‐doping. This work provides an effective strategy for designing heterostructured electrocatalysts with high catalytic activity and stability desired for reactions that may occur under harsh conditions.     

Three‐Dimensional Structures of MoS2 Nanosheets with Ultrahigh Hydrogen Evolution Reaction in Water Reduction

The hydrogen evolution reaction in an alkaline environment using a non‐precious catalyst with much greater efficiency represents a critical challenge in research. Here, a robust and highly active system for hydrogen evolution reaction in alkaline solution is reported by developing MoS₂ nanosheet arrays vertically aligned on graphene‐mediated 3D Ni networks. The catalytic activity of the 3D MoS₂ nanostructures is found to increase by 2 orders of magnitude as compared to the Ni networks without MoS₂. The MoS₂ nanosheets vertically grow on the surface of graphene by employing tetrakis(diethylaminodithiocarbomato)molybdate(IV) as the molybdenum and sulfur source in a chemical vapor deposition process. The few‐layer MoS₂ nanosheets on 3D graphene/nickel structure can maximize the exposure of their edge sites at the atomic scale and present a superior catalysis activity for hydrogen production. In addition, the backbone structure facilitates as an excellent electrode for charge transport. This precious‐metal‐free and highly efficient active system enables prospective opportunities for using alkaline solution in industrial applications.     

In Situ Grown Pristine Cobalt Sulfide as Bifunctional Photocatalyst for Hydrogen and Oxygen Evolution

Herein, transition metal chalcogenides of pristine cobalt sulfides are rationally designed to act as robust bifunctional photocatalysts for visible‐light‐driven water splitting for the first time. Through moderate solvothermal route, cobalt sulfides are synthesized in situ growth and observed by scanning electron microscope image analysis. Noteworthily, 3D hierarchical cobalt sulfides acting as bifunctional photocatalysts are implemented to catalyze the visible‐light‐driven oxygen evolution reaction and hydrogen evolution reaction. This efficient, earth‐abundant, and nonnoble water splitting catalyst for artificial photosynthesis is thoroughly analyzed by various spectroscopic techniques with the aim of investigating its photocatalytic mechanism under visible‐light illumination. The main catalyst of CoS‐2 exhibits considerable H₂ evolution rate of 1196 µmol h^?1 g^?1 and O₂ yield of 63.5%. The efficient activity is attributed to the effective electron transfer between the photosensitizer and catalyst, which is verified by transient absorption experiments. The effective electron transfer between the photosensitizer and catalyst during water oxidation is verified by the dramatic decline of [Ru(bpy)₃]³⁺ concentration in the presence of the catalyst CoS‐2. At the same time, transient absorption experiments support a rapid electron transfers from ³EY* (excited photosensitizer eosin‐Y) to the catalyst CoS‐2 for efficient hydrogen evolution.