Alkaline Hydrogen Evolution Reaction Research Articles

Synthesis Framework for Designing PtPdCoNiMn High-Entropy Alloy: A Stable Electrocatalyst for Enhanced Alkaline Hydrogen Evolution Reaction.

High entropy alloys (HEAs) are an emerging class of advanced materials characterized by their multifunctionality and potential to replace commercial catalysts in electrocatalytic water splitting. The synergy among the various alloyed elements in HEAs makes them particularly promising for applications in electrocatalysis. However, preparation of HEA via bottom-up approaches by avoiding the formation of mono, di, and tri metallic alloys in the nanoscale is challenging. This aspect is addressed, in this study by exploring the logical selection of solvents, reducing agents, and capping agents, along with their relative fractions, in the solvothermal synthesis of the HEA comprising platinum-palladium-cobalt-nickel-manganese (PtPdCoNiMn). It is established that the reducing capabilities of both the solvent and reducing agent are crucial for the reduction of each metal to form a single-phase HEA. The synthesized HEA (20 wt.%)/functionalized carbon (FC) demonstrates excellent performance as an HER catalyst, exhibiting a low overpotential of 48.7mV at -10 mA cm-2 in an alkaline electrolyte. This performance is characterized by high reaction kinetics and stability at elevated current densities. Furthermore, the catalyst shows impressive performance in both simulated and actual seawater. This development reduces the reliance on platinum while enhancing the long-term durability and catalytic efficiency of the electrocatalyst.

Dual Modulation of Hydroxyl Action on Ruthenium Surface by Single‐Atom Supports for Alkaline H2 Evolution

AbstractRuthenium (Ru)‐based catalysts are known to accelerate the slow kinetics of the alkaline hydrogen evolution reaction (HER). However, enhancing the transfer kinetics of adsorbed hydroxyl (OHad) remains challenging. Herein, a dual‐regulation strategy is presented to alleviate OH blockage on the catalyst surface, using a cluster‐level Ru electrocatalyst supported by single‐atom CoN4 generated in situ on carbon nanotubes (CNTs). Experimental and theoretical studies demonstrate that introducing oxophilic single‐atom CoN4 can mitigate the strong interaction between Ru and OHad by directly competing for OHad on the Ru surface, thereby preventing Ru site poisoning. Meanwhile, single‐atom CoN4 effectively modifies the electronic structure of Ru atomic clusters (ACs), indirectly optimizing the energy barriers for OH desorption at the Ru interface and promoting OHad release. The electronic interaction between Ru ACs and CoN4 also inhibits Ru atom migration, significantly enhancing catalytic stability. The resulting catalyst shows excellent HER activity at 10 mA cm−2 with a low overpotential of 15 mV in alkaline solution and remains stable at 200 mA cm−2 for over 1000 h. An alkaline anion‐exchange membrane water electrolyzer (AEMWE) using this catalyst can exhibit an ultralow potential (1.785 V at 1 A·cm−2) and high stability at 500 mA·cm−2.

Unconventional Hexagonal Close-Packed High-Entropy Alloy Surfaces Synergistically Accelerate Alkaline Hydrogen Evolution.

Accelerating the alkaline hydrogen evolution reaction (HER), which involves the slow cleavage of HO-H bonds and the adsorption/desorption of hydrogen (H*) and hydroxyl (OH*) intermediates, requires developing catalysts with optimal binding strengths for these intermediates. Here, the unconventional hexagonal close-packed (HCP) high-entropy alloy (HEA) atomic layers are prepared composed of five platinum-group metals to enhance the alkaline HER synergistically. The breakthrough is made by layer-by-layer heteroepitaxial deposition of subnanometer RuRhPdPtIr HEA layers on the HCP Ru seeds, despite the thermodynamic stability of Rh, Pd, Pt, and Ir in a face-centered cubic (FCC) structure except for Ru. The synchrotron X-ray absorption spectroscopy (XAS) confirms the atomic mixing and coordination environment of HCP RuRhPdPtIr HEA. Most importantly, they exhibit notable improvements in both electrocatalytic activity and durability for the HER in an alkaline environment, as compared to their FCC RuRhPdPtIr counterparts. Electrochemical measurements, operando XAS analysis, and density functional theory unveil that the binding strengths of H* and OH* intermediates on the active Pt and Ir sites can be weakened and strengthened to a moderate level, respectively, by mixing non-active Ru, Rh, and Pd atoms with Pt and Ir atoms within the HCP HEA with strong synergistic electronic effects.

Surface-Reconstructed CdNNi3 Antiperovskite Electrocatalyst: Unlocking Ampere-Level Current Density for Hydrogen Evolution.

Developing conductive electrocatalysts is crucial for decreasing the ohmic loss induced by electric resistance of the catalyst layer in the large-current-density hydrogen evolution reaction (HER), which has been overlooked previously. In this study, we screen a highly conductive antiperovskite CdNNi3 with negligible ohmic loss, as a highly active and durable HER electrocatalyst capable of unlocking ampere-scale current densities. CdNNi3 exhibits an impressive activity (an overpotential of 235 mV) at 1 A cm-2 and maintains its performance steadily at an ampere-scale current density (at 1 A cm-2 over 400 h). Besides, the CdNNi3-enabled anion-exchange membrane water electrolyzer outperforms that of the benchmark Pt/C, evidenced by a reduced cell voltage of 160 mV at 1 A cm-2, and presents a favorable stability at 1 A cm-2. Importantly, this study experimentally discovers the dynamic surface reconstruction phenomena of antiperovskite nitrides during alkaline HER. Theoretical analysis suggests that the presence of Cd in the reconstructed surface effectively adjusts the local electronic configuration of active sites, which promotes the adsorption of OH and reduces the binding strength to H, thereby facilitating the water dissociation step and reducing the energy barrier of the potential-determining step in the HER process.

Constructing Ru-Co2P Lewis Acid-Base Pairs to Prompt Hydrogen Evolution Reaction in Alkaline Seawater Electrolyte.

Seawater electrolysis is an ideal approach to generating green hydrogen. Nevertheless, the sluggish kinetics of water dissociation and the detrimental chlorine chemistry environment are serious obstructions for industrial applications. Herein, constructing unique (Co) Lewis acid and (Ru-P) base pair sites in Ru-Co2P decorated on nitrogen and phosphorus co-doped carbon (Ru-Co2P/NPC) significantly optimizes the energy barrier of water dissociation and enhances the anti-corrosive ability for alkaline seawater splitting. As expected, the optimal Ru-Co2P/NPC-2 exhibits exceptional hydrogen evolution reaction (HER) performances with overpotentials as low as 22.0 and 26.0mV to derive 10 mAcm-2 and operate steadily (@ 50 mAcm-2) over 30 h in alkaline and alkaline seawater electrolytes. The experimental and theoretical results elucidate that Co acting as Lewis acid sites prompts the water adsorption and breakage of the H─O bond, whereas Ru-P as Lewis base sites facilitates the hydrogen desorption in alkaline media. Furthermore, modulated chemical microenvironments can be beneficial to hinder chloride corrosion on the active sites of catalysts. This work sheds light on the rational construction of a highly efficient electrocatalyst for alkaline HER in seawater.

Cu- and S-Doped Heteropolyacid Co2Mo10 as Electrocatalysts for Efficient Hydrogen Evolution.

This study employed polyoxometalate Co2Mo10 as a precursor and a two-step method to prepare carbon cloth-supported CuxS-CoS2-MoS2 materials. The morphology and structure of the materials were characterized using XRD, XPS, SEM, TEM, and other techniques. Interestingly, changes in the reducing gas during the calcination process could adjust the product morphology, thereby altering catalytic activity. Electrochemical results indicated that the CuxS-CoS2-MoS2 nanomaterials prepared under an NH3 atmosphere exhibited unique morphology and structural advantages. They demonstrated significant electrocatalytic activity for the hydrogen evolution reaction (HER) in alkaline and acidic electrolytes (overpotentials of 108 and 196 mV at a current density of 10 mA cm-2, lower than the overpotentials of 143 and 226 mV obtained under a H2-Ar atmosphere during calcination) and excellent long-term durability. These findings provide insights and methods for synthesizing multicomponent electrocatalysts with enhanced catalytic performance.

Electronic Structure Engineering of RuNi Alloys Decrypts Hydrogen and Hydroxyl Active Site Separation and Enhancement for Efficient Alkaline Hydrogen Evolution.

Rational design of the active sites of hydrolysis dissociation intermediates to weaken their active site competition and toxicity is a key challenge to achieve efficient and stable hydrogen evolution reaction (HER) in ruthenium-containing alloys. Density Functional Theory (DFT) simulations reveal that the transfer of the d-band electrons from Ru to Ni in RuNi alloys results in a Gibbs free energy of -0.12eV for the Ru0.250Ni Fcc-site H*. In addition, the high spin state of the electrons outside the Ru nucleus strengthens the adsorption of OH* on the Ru─Ni bond, which weakens the active-site competition and toxicity successfully. This theoretical prediction is confirmed by electrodeposition of prepared aRuxNi, and the RuNi alloys obtained by Ru atom doping have excellent HER properties. aRu0.250Ni has overpotentials of 38 and 162.4mV at -10 and -100mAcm-2, respectively, and can be stably operated at -100mAcm-2 Dual-electrode system aRu0.250Ni//bRu0Ni demonstrates an ultra-low battery voltage (1.86V @500mAcm-2) and excellent stability (24h@300mAcm-2). This holistic work resolves the mechanism of active site separation and strengthening in RuNi alloys, and provides a new design idea for the preparation of highly efficient alkaline HER electrodes.

Super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle with abundant plane- and edge-type active interfaces for robust all-pH hydrogen evolution

Transition metal sulfides (TMSs) are primitive composition of biocatalysts that are active for molecular hydrogen production. The development of non-precious TMSs with appropriate spatial ordering has great potentials to contribute high-level hydrogen generation. Herein, super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle (Super-NiS/WS2/Ni3S4) with high spatial ordering and abundant plane- and edge-type WS2-NiS and WS2-Ni3S4 heterointerfaces were elaborately constructed though manipulating the sequential dissociation of phosphotungstic acid (PW12) as W precursor and nickel foam as Ni precursor in one pot. When evaluated for the electrocatalytic hydrogen evolution reaction (HER), the Super-NiS/WS2/Ni3S4 only required overpotentials of 57, 95, and 151 mV to drive HER in alkaline, acid, and neutral media, respectively, and presented favorable reaction kinetics and test stability. The theoretical and experimental results verify the adsorption and dissociation of water molecules are preferential on WS2-plane-related heterointerfaces. The Gibbs free energy (ΔGH*) analysis indicated the WS2-plane-NiS interface is thermodynamically optimal for HER. Moreover, the collaborations of the abundant plane- and edge-type active interfaces, the open nanosheet-based vertical array, and the phosphorus doping in Super-NiS/WS2/Ni3S4 strengthen mass transport and electron transfer in electrocatalysis. The polyoxometalates-based synthetic strategy will inspire the new vision for the rational design and construction of advanced functional materials.

Engineering multiple nano-twinned high entropy alloy electrocatalysts toward efficient water electrolysis

Inducing defects in high entropy alloys (HEAs) has been recognized as a promising approach for tuning surface energetics and catalytic activities. However, the comprehensive understanding and facile synthetic methods for defect-rich HEAs remain challenging. Herein, we present an interstitial-atom engineering strategy that involves interstitial atom doping to synthesize B-doped FeCoNiCuMoB HEA films containing abundant multiple nano-twin boundaries. The resulting fivefold-twinned FeCoNiCuMoB catalyst exhibits exceptional performance in alkaline hydrogen evolution reaction (HER, 26mV at -10 mA cm-2) and oxygen evolution reaction (OER, 201mV at 10mAcm-2). Notably, the two-electrode electrolyzer composed of the FeCoNiCuMoB film electrodes achieved the 10mAcm-2 at an ultralow cell voltage (1.48V) for water electrolysis, simultaneously maintaining long-term durability. Through in-situ Raman spectroscopy, X-ray absorption spectroscopy (XAS), electrochemical analyses, and density functional theory (DFT) calculations, we elucidate that the unique twin boundaries play a crucial role in tailoring surficial electronic structures. Moreover, election-rich B atoms display optimized atomic configurations, synergistically contributing to a thermodynamically favourable HER/OER pathway. This work provides a platform via interstitial-atom engineering for designing exceptional HEA catalysts, integrating planar defects and electronic effects, to enhance the efficiencies in water electrolysis applications.

Engineering the interfacial hetero-structure for high-current-density hydrogen evolution

Modulating the hetero-structures with abundant interfaces in catalyst is a feasible but challenging strategy to improve the catalytic performance. In this work, a highly efficient catalyst (R-CoMoOx/Ni (Co)) was prepared with plentiful interfacial structures to accelerate the hydrogen evolution reaction (HER), which contained both reduced CoO and MoO2 as a R-CoMoOx substrate and metallic Ni (Co) particles as the catalytic center. The combination of CoO and MoO2 with a Co-O-Mo local structure in R-CoMoOx led to an electron-enriched Co center to catch the dissociated H+, while the abundant interfacial interaction between R-CoMoOx and Ni (Co) could accelerate the charge transfer and then facilitate the production of H2 through a fast Volmer-Tafel pathway. As a result, the integrated R-CoMoOx/Ni (Co) catalyst could drive alkaline HER with ultra-low overpotentials of 16 mV for 10 mA cm−2 (25 °C) and 186 mV for 1000 mA cm−2 (60 °C), respectively, with a good stability over 100 h. Moreover, by coupling with RuO2 electrode in an anion exchange membrane system, it could achieve 1000 mA cm−2 at 1.78 V for overall water splitting with a high energy conversion efficiency of 70.4 %. The H2 production cost at 1000 mA cm−2 was merely $ 0.952 per gasoline gallon equivalent, much less than the target cost of the US Department of Energy.

Tailoring Hydrogen Adsorption via Charge Transfer at Bimetallic Cr0.48Ru0.52 Alloy Nanoparticles Decorated on Carbon Nanofiber for Enhanced Hydrogen Evolution Catalysis

Designing and synthesizing highly efficient and stable electrocatalysts for the hydrogen evolution reaction (HER) is crucial for the practical and large-scale application of hydrogen sources. Recent research has focused on tuning the electronic structure of electrocatalysts to achieve optimal HER activity, with particular emphasis on interfacial engineering to induce electron transfer and optimize HER kinetics. In this study, as part of research into heterointerface engineering, bimetallic Cr0.48Ru0.52 alloy nanoparticles decorated on carbon nanofibers (Cr0.48Ru0.52/CNFs) were fabricated through a simple electrospinning and post-calcination process to serve as an efficient alkaline HER catalyst. The Cr0.48Ru0.52/CNFs demonstrated exceptional electrocatalytic HER performance, with an overpotential of only 13 mV at −10 mA cm−2 and a Tafel slope of 60.8 mV dec−1, indicating high catalytic activity compared to commercial benchmark catalysts (i.e., Ru/C and Pt/C). First-principles density functional theory calculations support these results, revealing that Cr0.48Ru0.52 balances proton reduction (Volmer step) and H* desorption (Tafel/Heyrovsky step) processes during electrocatalysis, as evidenced by the near-zero hydrogen adsorption (ΔGH*) value (ca. −0.11 eV). Therefore, this study highlights that Cr0.48Ru0.52/CNFs, with noble Ru comprising only half of the total metal content, can promote optimal HER kinetics under alkaline condition.

Hydrogen Evolution Reactivity of Pentagonal Carbon Rings and p‐d Orbital Hybridization Effect with Ru

AbstractTopological defects are inevitable existence in carbon‐based frameworks, but their intrinsic electrocatalytic activity and mechanism remain under‐explored. Herein, the hydrogen evolution reaction (HER) of pentagonal carbon‐rings is probed by constructing pentagonal ring‐rich carbon (PRC), with optimized electronic structures and higher HER activity relative to common hexagonal carbon (HC). Furthermore, to improve the reactivity, we couple Ru clusters with PRC (Ru@PRC) through p‐d orbital hybridization between C and Ru atoms, which drives a shortcut transfer of electrons from Ru clusters to pentagonal rings. The electron‐deficient Ru species leads to a notable negative shift in d‐band centers of Ru and weakens their binding strength with hydrogen intermediates, thus enhancing the HER activity in different pH media. Especially, at a current density of 10 mA cm−2, PRC greatly reduces alkaline HER overpotentials from 540 to 380 mV. And Ru@PRC even exhibits low overpotentials of 28 and 275 mV to reach current densities of 10 and 1000 mA cm−2, respectively. Impressively, the mass activity and price activity of Ru@PRC are 7.83 and 15.7 times higher than that of Pt/C at the overpotential of 50 mV. Our data unveil the positive HER reactivity of pentagonal defects and good application prospects.

Mo Migration‐Induced Crystalline to Amorphous Conversion and Formation of RuMo/NiMoO4 Heterogeneous Nanoarray for Hydrazine‐Assisted Water Splitting at Large Current Density

AbstractManipulating the atomic structure of the catalyst and tailoring the dissociative water‐hydrogen bonding network at the catalyst‐electrolyte interface is essential for propelling alkaline hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR), but remains a great challenge. Herein, we constructed an advanced a‐RuMo/NiMoO4/NF heterogeneous electrocatalyst with amorphous RuMo alloy nanoclusters anchored to amorphous NiMoO4 skeletons on Ni foam by a heteroatom implantation strategy. Theoretical calculations and in situ Raman tests show that the amorphous and alloying structure of a‐RuMo/NiMoO4/NF not only induces the directional evolution of interfacial H2O, but also lowers the d‐band center (from −0.43 to −2.22 eV) of a‐RuMo/NiMoO4/NF, the Gibbs free energy of hydrogen adsorption (ΔGH*, from −1.29 to −0.06 eV), and the energy barrier of HzOR (ΔGN2(g)=1.50 eV to ΔGN2*=0.47 eV). Profiting from these favorable factors, the a‐RuMo/NiMoO4/NF exhibits excellent electrocatalytic performances, especially at large current densities, with an overpotential of 13 and 129 mV to reach 10 and 1000 mA cm−2 for HER. While for HzOR, it needs only −91 and 276 mV to deliver 10 and 500 mA cm−2, respectively. Further, the constructed a‐RuMo/NiMoO4/NF||a‐RuMo/NiMoO4/NF electrolyzer demands only 7 and 420 mV to afford 10 and 500 mA cm−2.

Synergistic Alkaline Hydrogen Evolution Catalysis over MoC Triggered by Doping Single Ru Atoms

AbstractThe rational design of single atom‐based catalysts and precise elucidation of the synergistic interaction between the metal site and substrate are pivotal to identifying the real active sites and explicating the catalytic mechanisms at the atomic scale, thus contributing to the development of high‐performance catalysts for diverse industrial implementations. Herein, a Ru single‐atom doping strategy is developed to activate the MoC substrate with superior hydrogen evolution reaction (HER) activity in an alkaline medium. The atomically dispersed Ru sites are elaborately doped into MoC nanoparticles loaded on 3D N‐doped carbon nanoflowers (Ru‐SAs@MoC/NCFs hereafter). The experimental results and theoretical calculations manifest that the atomically isolated Ru dopants can effectively trigger the Mo sites with thermodynamically favorable water adsorption/dissociation energies and facilitate the OH− desorption on Ru sites and H adsorption on N sites, thus synergistically expediating the overall alkaline HER kinetics. As such, the well‐designed Ru‐SAs@MoC/NCFs demonstrate extraordinary HER activity with a low overpotential of 16 mV at 10 mA cm−2 in 1.0 m KOH electrolyte, outperforming Pt/C benchmark and a vast of molybdenum/ruthenium‐based HER catalysts reported to date. These findings disclose the alkaline HER mechanistic induced by the atomic doping modulation and suggest a design principle of high‐efficiency electrocatalysts via the atomic‐level manipulation leverage.

Efficient Solvothermal Synthesis of Defect-Rich Cu-BTC•MOF with Enhanced Electrocatalytic Activity in Alkaline Hydrogen Evolution Reaction

Efficient Solvothermal Synthesis of Defect-Rich Cu-BTC•MOF with Enhanced Electrocatalytic Activity in Alkaline Hydrogen Evolution Reaction

MXene quantum dots-Co(OH)2 heterojunction stimulated Co2+δ sites for boosted alkaline hydrogen evolution

Persevering structural stability of the active species after phase reconfiguration poses a key challenge for various sustainable catalytic systems. In this study, we construct a robust β-Co(OH)2 electrocatalyst via self-adaptive coordination of MXene quantum dots (MQDs) during phase transition from the Co2(OH)3Cl precursor to β-Co(OH)2 (MQDs/β-Co(OH)2/Co foam). The heterojunction induced the excellent electron transfer, causing the lattice strain of β-Co(OH)2, and the accumulated electrons at the MQDs end regulated the electronic density of Co sites (Co2+δ), reversing the structural instability of β-Co(OH)2 within the applied reduction potential range. Furthermore, density functional theory calculation confirms the role of well-matched heterogeneous interfaces in HER. The result shows the high-valance Co2+δ sites promote adsorption and dissociation of H2O, increasing proton supply and accelerating reaction rate. Concurrently, MQDs facilitate the adsorption of hydrogen intermediates and H2 generation. Our architected catalyst exhibited exceptional alkaline hydrogen evolution reactions (HERs) performance (91 mV@10 mA cm−2) and superior stability outperforms most reported β-Co(OH) 2-based catalysts. Our work demonstrates the efficacy of MQDs as co-catalysts in enhancing the activity and structural stability of catalysts.

Multi-synergy enabling Ni-doped MoS2@N-doped carbon composite as versatile catalysts toward hydrogen production and photovoltaics

Construction of efficient non-precious catalyst with desired chemical composition and well-defined nanostructure is of great essential to enhance the kinetics of hydrogen evolution reaction (HER) and triiodide (I3−) reduction reaction (IRR), which is conducive to promote the development of green hydrogen production and obtain impressive photovoltaic performance of dye-sensitized solar cells (DSSCs). Herein, ZIF-8 derived N-doped carbon (NC) wrapped with two-dimensional Ni-doped MoS2 nanosheets (Ni–MoS2@NC) are elaborately designed. The catalytic activity of Ni–MoS2@NC for HER and IRR are significantly improved by modifying electronic structure through heteroatom doping. The optimized Ni–MoS2@NC has lower overpotential of 122 mV at 10 mA cm−2 in comparison with counterpart. Meanwhile, the power conversion efficiency (PCE) of DSSCs based on Ni–MoS2@NC CE catalyst is comparable to that of Pt. Density functional theory (DFT) calculation is used to unveil the mechanism of Ni–MoS2@NC for alkaline HER and IRR, namely, the multi-synergy of various sites endows Ni–MoS2@NC with appropriate Gibbs free energy for H∗ adsorption and water dissociation energy, while the top and interfacial S sites of Ni–MoS2@NC are responsible for the adsorption and activation of I3−. Our work provides a feasible route to design efficient catalysts in the field of energy conversion and understand mechanism.

Sustainable hydrogen production with synergistic electron transfer enhancement in nickel-based alkaline HER electrocatalyst empowered by graphene oxide

The hydrogen evolution reaction (HER) plays a crucial role in driving forward the transition to a hydrogen-based economy by providing a means to generate pure hydrogen. However, the efficient and cost-effective production of hydrogen via HER faces significant challenges, particularly at the cathode. To address these challenges, we produced a hybrid material – 2D graphene oxide (GO) sheets coated onto nickel sulfide (NiS) microspheres anchored on Ni Foam (GO@NiS/Ni Foam) using a straightforward synthesis technique. Our research highlights the significant influence of the interaction between GO and NiS on the performance of HER, attributed to the enhancement of electron transport at the interface. Furthermore, the GO@NiS/Ni Foam composite exhibits remarkable durability over extended periods, maintaining its superior functionality for up to 40 h of continuous operation. This underscores its potential for practical implementation in efficient water-splitting processes, offering a promising solution to the challenges hindering widespread adoption of hydrogen technology.

Application of Hydrogen Spillover to Enhance Alkaline Hydrogen Evolution Reaction

AbstractAlkaline water splitting has shown great potential for industrial‐scale hydrogen production. However, its broad application is constrained by hydrogen evolution reaction (HER) electrocatalysts, which struggle to achieve optimal current density at low overpotential. The utilization of the hydrogen spillover effect to augment the performance of HER represents a burgeoning area of research. Although previous studies mainly focused on hydrogen spillover in acidic media, the latest studies have shown that hydrogen spillover also exists under alkaline conditions, and its role in improving HER performance cannot be ignored. This review examines the mechanisms of HER under acidic and alkaline conditions, elucidating the distinctive behavior of hydrogen spillover in these environments and its influence on catalytic processes. At the same time hydrogen spillover characterization methods are systematically summarized, these technologies for understanding and control of hydrogen release process provides strong support. Finally, the recent electrocatalysts that enhance the catalytic performance of alkaline HER by hydrogen spillover effect are comprehensively sorted out and summarized. This review not only demonstrate the practical value of hydrogen spillover under alkaline conditions, but also provide new directions for future design and optimization of electrocatalysts.

Coupled Lattice‐Expanded Ni and MoO2 Array for Efficient Alkaline Hydrogen Evolution

AbstractTransition metal oxides have attracted much attention due to their good electrical conductivity, high chemical stability, and easy electronic structure modulation. However, it is still a great challenge to solve the problems of sluggish reaction kinetics and high overpotential in the alkaline hydrogen evolution reaction (HER) due to their poor intrinsic activity. Herein, a lattice‐expanded Ni‐decorated MoO2 array (Ni‐MoO2‐700) catalyst is prepared for the alkaline HER. Unlike most of the reported literature, the decoration of metal heteroatoms may lead to lattice expansion of the carrier catalyst. In contrast, lattice expansion of Ni is also achieved by adjusting the annealing temperature in this work. The Ni‐induced lattice‐expanding effect can not only modulate the electronic structure of the catalyst but also accelerate electron transfer during the reaction, thus increasing its intrinsic activity for the HER. As a result, Ni‐MoO2‐700 exhibits significantly enhanced catalytic activity with an overpotential of 74.9 mV at 10 mA cm−2 in 1.0 m KOH, which is far superior to that of most of the reported advanced Ni‐ and Mo‐based materials. This work provides deep intrinsic insight and a great opportunity to design efficient transition metal oxide catalysts for the alkaline HER.