Engineering the Electrical Conductivity of Lamellar Silver-Doped Cobalt(II) Selenide Nanobelts for Enhanced Oxygen Evolution

Electrochemical Synthesis of Cation Vacancy-Enriched Ultrathin Bimetallic Oxyhydroxide Nanoplatelets for Enhanced Water Oxidation

Metal cation vacancies, a kind of structural defect, are viewed as a promising strategy for regulating the electronic properties to enhance the catalytic activity. However, the effective introduction of cation vacancies into electrocatalysts still remains a challenge. Herein, we present and elucidate a facile "fast reduction and in situ phase transformation" strategy at room temperature to simultaneously introduce abundant metal cation vacancies (cobalt vacancies and iron vacancies) into Co_0.5Fe_0.5OOH electrocatalysts. The incorporation of the Fe element could tailor the micrometer-sized ultrathin CoOOH platelets into nanometer-sized ultrathin Co_0.5Fe_0.5OOH platelets, and the tailoring process is accompanied with the generation of numerous cation vacancies. The defect degree of CoOOH could be effectively tuned by the incorporation of Fe, resulting in more active sites and lower energy barrier, and thereby the intrinsic catalytic activity of electrocatalysts was further enhanced. Compared to CoOOH, the optimized nanometer-sized ultrathin Co_0.5Fe_0.5OOH platelets (Co_0.5Fe_0.5OOH-NSUPs) require a smaller overpotential of 220 mV at a current density of 20 mA cm^-2, lower Tafel slope of 38.2 mV dec^-1, and better long-term durability without obvious decay for more than 200 h at a high current density of 40 mA cm^-2. The electrochemical performances are equal to or better than that of the reported first-class electrocatalysts. More importantly, this work provides new perspective for designing and fabricating efficient multimetal electrocatalysts in large scale.

Rapid Fabrication of Ni/NiO@CoFe Layered Double Hydroxide Hierarchical Nanostructures by Femtosecond Laser Ablation and Electrodeposition for Efficient Overall Water Splitting

The development of simple and effective methods for the rapid preparation of electrocatalysts for overall water splitting from earth-abundant elements is an important and challenging task. A facile and ultrafast two-step method was developed to prepare a Ni/NiO@CoFe layered double hydroxide hierarchical nanostructure (NCF) within a few minutes by femtosecond laser ablation and electrodeposition. In 1 m KOH solution, the optimized NCF catalysts show a low overpotential of 230 mV for the oxygen evolution reaction (OER) at a current density of 10 mA cm^-2 with a low Tafel slope of 34.3 mV dec^-1 , indicating fast and efficient OER kinetics. Owing to the synergistic effect between NiO and CoFe layered double hydroxide, the hydrogen evolution reaction performance of the NCF was also improved. The synthesized electrocatalysts were further utilized in overall water splitting with a potential of only 1.56 V at a current density of 10 mA cm^-2 and excellent durability, better than that of the commercial RuO₂ (+)//Pt/C(-) system. The present work provides new insights on the rapid and facile preparation of efficient electrocatalysts for overall water splitting on a large scale.

Metal Organic Framework-Templated Synthesis of Bimetallic Selenides with Rich Phase Boundaries for Sodium-Ion Storage and Oxygen Evolution Reaction

Two-phase or multiphase compounds have been evidenced to exhibit good electrochemical performance for energy applications; however, the mechanism insights into these materials, especially the performance improvement by engineering the high-active phase boundaries in bimetallic compounds, remain to be seen. Here, we report a bimetallic selenide heterostructure (CoSe₂/ZnSe) and the fundamental mechanism behind their superior electrochemical performance. The charge redistribution at the phase boundaries of CoSe₂/ZnSe was experimentally and theoretically proven. Benefiting from the abundant phase boundaries, CoSe₂/ZnSe exerts low Na⁺ adsorption energy and fast diffusion kinetics for sodium-ion batteries and high activity for oxygen evolution reaction. As expected, excellent sodium storage capability, specifically a superb cyclic stability of up to 800 cycles for the Na₃V₂(PO₄)₃∥CoZn-Se full cell, and efficient water oxidation with a small overpotential of 320 mV to reach 10 mA cm^-2 were obtained. This work demonstrates the importance of phase boundaries in bimetallic compounds to boost the performance in various fields.

Evaluating DNA Derived and Hydrothermally Aided Cobalt Selenide Catalysts for Electrocatalytic Water Oxidation

Electrocatalysts with engaging oxygen evolution reaction (OER) activity with lesser overpotentials are highly desired to have increased cell efficiency. In this work, cobalt selenide catalysts were prepared utilizing both wet-chemical route (CoSe and CoSe-DNA) and hydrothermal route (Co_0.85Se-hyd). In wet-chemical route, cobalt selenide is prepared with DNA (CoSe-DNA) and without DNA (CoSe). The morphological results in the wet-chemical route had given a clear picture that, with the assistance of DNA, cobalt selenide had formed as nanochains with particle size below 5 nm, while it agglomerated in the absence of DNA. The morphology was nano networks in the hydrothermally assisted synthesis. These catalysts were analyzed for OER activity in 1 M KOH. The overpotentials required at a current density of 10 mA cm^-2 were 352, 382, and 383 mV for Co_0.85Se-hyd, CoSe, and CoSe-DNA catalysts, respectively. The Tafel slope value was lowest for Co_0.85Se-hyd (65 mV/dec) compared to CoSe-DNA (71 mV/dec) and CoSe (80 mV/dec). The chronoamperometry test was studied for 24 h at a potential of 394 mV for Co_0.85Se-hyd and was found to be stable with a smaller decrease in activity. From the OER study, it is clear that Co_0.85Se was found to be superior to others. This kind of related study can be useful to design the catalyst with increased efficiency by varying the method of preparation.

Gas Bubbles in Electrochemical Gas Evolution Reactions

Electrochemical gas evolution reactions are of vital importance in numerous electrochemical processes including water splitting, chloralkaline process, and fuel cells. During gas evolution reactions, gas bubbles are vigorously and constantly forming and influencing these processes. In the past few decades, extensive studies have been performed to understand the evolution of gas bubbles, elucidate the mechanisms of how gas bubbles impact gas evolution reactions, and exploit new bubble-based strategies to improve the efficiency of gas evolution reactions. In this feature article, we summarize the classical theories as well as recent advancements in this field and provide an outlook on future research topics.

Electron Correlations Engineer Catalytic Activity of Pyrochlore Iridates for Acidic Water Oxidation

The development of highly efficient oxygen-evolving catalysts compatible with powerful proton-exchange-membrane-based electrolyzers in acid environments is of prime importance for sustainable hydrogen production. In this field, understanding the role of electronic structure of catalysts on catalytic activity is essential but still lacking. Herein, a family of pyrochlore oxides R₂ Ir₂ O₇ (R = rare earth ions) is reported as acidic oxygen-evolving catalysts with superior-specific activities. More importantly, it is found that the intrinsic activity of this material significantly increases with the R ionic radius. Electronic structure studies reveal that the increased R ionic radius weakens electron correlations in these iridate oxides. This weakening induces an insulator-metal transition and an enhancement of IrO bond covalency, both of which promote oxygen evolution kinetics. This work demonstrates the importance of engineering the electron correlations to rationalize the catalytic activity toward water oxidation in strongly correlated transition-metal oxides.

The oxygen evolution reaction enabled by transition metal phosphide and chalcogenide pre-catalysts with dynamic changes

Dynamic morphological, structural and compositional changes will occur when transition metal phosphides and chalcogenides are used to catalyze the oxygen evolution reaction, which can substantially enhance their electrocatalytic performance.

Noble-Metal-Free Electrocatalysts for Oxygen Evolution

Oxygen evolution reaction (OER) plays a vital role in many energy conversion and storage processes including electrochemical water splitting for the production of hydrogen and carbon dioxide reduction to value-added chemicals. IrO₂ and RuO₂ , known as the state-of-the-art OER electrocatalysts, are severely limited by the high cost and low earth abundance of these noble metals. Developing noble-metal-free OER electrocatalysts with high performance has been in great demand. In this review, recent advances in the design and synthesis of noble-metal-free OER electrocatalysts including Ni, Co, Fe, Mn-based hydroxides/oxyhydroxides, oxides, chalcogenides, nitrides, phosphides, and metal-free compounds in alkaline, neutral as well as acidic electrolytes are summarized. Perspectives are also provided on the fabrication, evaluation of OER electrocatalysts and correlations between the structures of the electrocatalysts and their OER activities.

Enhanced activity of selenocyanate-containing transition metal chalcogenides supported by nitrogen-doped carbon materials for the oxygen reduction reaction

The SeCN⁻ containing transition metal chalcogenides supported by nitrogen-doped carbon catalyzes the ORR activity.

Grafting Cobalt Diselenide on Defective Graphene for Enhanced Oxygen Evolution Reaction

Cobalt diselenide (CoSe₂) has been demonstrated to be an efficient and economic electrocatalyst for oxygen evolution reaction (OER) both experimentally and theoretically. However, the catalytic performance of up-to-now reported CoSe₂-based OER catalysts is still far below commercial expectation. Herein, we report a hybrid catalyst consisting of CoSe₂ nanosheets grafted on defective graphene (DG). This catalyst exhibits a largely enhanced OER activity and robust stability in alkaline solution (overpotential at 10 mA cm⁻²: 270 mV; Tafel plots: 64 mV dec⁻¹). Both experimental evidence and density functional theory calculations reveal that the outstanding OER performance of this hybrid catalyst can be attributed to the synergetic effect of exposed cobalt atoms and carbon defects (electron transfer from CoSe₂ layer to defect sites at DG). Our results suggest a promising way for the development of highly efficient and low-cost OER catalysts based on transition metal dichalcogenides.

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A hybrid catalyst with in-plane CoSe₂/defective graphene heterostructures

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The catalyst exhibits an excellent and stable oxygen evolution reaction (OER) activity

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Enhanced OER performance is due to the synergy of exposed cobalt atoms and carbon defects

Dynamic Structure Evolution of Composition Segregated Iridium-Nickel Rhombic Dodecahedra toward Efficient Oxygen Evolution Electrocatalysis

The anodic oxygen evolution reaction (OER) is central to various energy conversion devices, but the investigation of the dynamic evolution of catalysts in different OER conditions remains quite limited, which is unfavorable for the understanding of the actual structure-activity relationship and catalyst optimization. Herein, we constructed monodispersed IrNi _x nanoparticles (NPs) with distinct composition-segregated features and captured their structural evolution in various OER environments. We decoded the interesting self-reconstruction of IrNi _x NPs during the OER, in which an Ir-skin framework is generated in an acidic electrolyte, while a Ni-rich surface layer is observed in an alkaline electrolyte owing to Ni migration. Benefiting from such self-reconstruction, considerable OER enhancements are achieved under both acidic and alkaline conditions. For comparison, IrNi _x nanoframes with Ir skins prepared by chemical etching show a similar structural evolution result in the acidic electrolyte, but a total different phenomenon in the alkaline electrolyte. By tracking the structural evolution of IrNi _x catalysts and correlating them with OER activity trajectories, the present work provides a significant understanding for designing efficient OER catalysts with controlled compositional distributions.

Hierarchically Porous Fe2 CoSe4 Binary-Metal Selenide for Extraordinary Rate Performance and Durable Anode of Sodium-Ion Batteries

Owing to high energy capacities, transition metal chalcogenides have drawn significant research attention as the promising electrode materials for sodium-ion batteries (SIBs). However, limited cycle life and inferior rate capabilities still hinder their practical application. Improvement of the intrinsic conductivity by smart choice of elemental combination along with carbon coupling of the nanostructures may result in excellence of rate capability and prolonged cycling stability. Herein, a hierarchically porous binary transition metal selenide (Fe2 CoSe4 , termed as FCSe) nanomaterial with improved intrinsic conductivity was prepared through an exclusive methodology. The hierarchically porous structure, intimate nanoparticle-carbon matrix contact, and better intrinsic conductivity result in extraordinary electrochemical performance through their synergistic effect. The synthesized FCSe exhibits excellent rate capability (816.3 mA h g-1 at 0.5 A g-1 and 400.2 mA h g-1 at 32 A g-1 ), extended cycle life (350 mA h g-1 even after 5000 cycles at 4 A g-1 ), and adequately high energy capacity (614.5 mA h g-1 at 1 A g-1 after 100 cycles) as anode material for SIBs. When further combined with lab-made Na3 V2 (PO4 )3 /C cathode in Na-ion full cells, FCSe presents reasonably high and stable specific capacity.

Bifunctional bamboo-like CoSe2 arrays for high-performance asymmetric supercapacitor and electrocatalytic oxygen evolution

Bifunctional bamboo-like CoSe₂ arrays are synthesized by thermal annealing of Co(CO₃)_0.5OH grown on carbon cloth in Se atmosphere. The CoSe₂ arrays obtained have excellent electrical conductivity, larger electrochemical active surface areas, and can directly serve as a binder-free electrode for supercapacitors and the oxygen evolution reaction (OER). When tested as a supercapacitor electrode, the CoSe₂ delivers a higher specific capacitance (544.6 F g^-1 at current density of 1 mA cm^-2) compared with CoO (308.2 F g^-1) or Co₃O₄ (201.4 F g^-1). In addition, the CoSe₂ electrode possesses excellent cycling stability. An asymmetric supercapacitor (ASC) is also assembled based on bamboo-like CoSe₂ as a positive electrode and active carbon as a negative electrode in a 3.0 M KOH aqueous electrolyte. Owing to the unique stucture and good electrochemical performance of bamboo-like CoSe₂, the as-assembled ACS can achieve a maximum operating voltage window of 1.7 V, a high energy density of 20.2 Wh kg^-1 at a power density of 144.1 W kg^-1, and an outstanding cyclic stability. As the catalyst for the OER, the CoSe₂ exhibits a lower potential of 1.55 V (versus RHE) at current density of 10 mA cm^-2, a smaller Tafel slope of 62.5 mV dec^-1 and an also outstanding stability.

Self-Template Synthesis of Co-Se-S-O Hierarchical Nanotubes as Efficient Electrocatalysts for Oxygen Evolution under Alkaline and Neutral Conditions

We develop a facile self-template synthetic method to construct hierarchical Co-Se-S-O (CoSe _xS_{2- x}@Co(OH)₂) nanotubes on a carbon cloth as a self-standing electrode for electrocatalytic oxygen evolution reaction (OER). In the synthetic process, separate selenization and sulfurization on the Co(OH)F precursor in different solvents have played an important role in constructing CoSe _xS_{2- x} (Co-Se-S) hierarchical nanotubes, which was further transformed into the nanotube-like Co-Se-S-O via an in situ electrochemical oxidation process. The Co-Se-S-O obtained by the Kirkendall effect through two stepwise anion-exchange reactions represents the first quaternary Co-Se-S-O nanotube array, which dramatically enhances its surface area and conductivity. Further, it only requires low overpotentials of 230 and 480 mV to achieve a 10 mA cm^-2 current density. The OER performance of Co-Se-S-O is much more efficient than that of its monochalcogenide counterparts, as well as the commercial benchmark catalyst IrO₂.

Conductive Tungsten Oxide Nanosheets for Highly Efficient Hydrogen Evolution

Exploring efficient and economical electrocatalysts for hydrogen evolution reaction is of great significance for water splitting on an industrial scale. Tungsten oxide, WO₃, has been long expected to be a promising non-precious-metal electrocatalyst for hydrogen production. However, the poor intrinsic activity of this material hampers its development. Herein, we design a highly efficient hydrogen evolution electrocatalyst via introducing oxygen vacancies into WO₃ nanosheets. Our first-principles calculations demonstrate that the gap states introduced by O vacancies make WO₃ act as a degenerate semiconductor with high conductivity and desirable hydrogen adsorption free energy. Experimentally, we prepared WO₃ nanosheets rich in oxygen vacancies via a liquid exfoliation, which indeed exhibits the typical character of a degenerate semiconductor. When evaluated by hydrogen evolution, the nanosheets display superior performance with a small overpotential of 38 mV at 10 mA cm^-2 and a low Tafel slope of 38 mV dec^-1. This work opens an effective route to develop conductive tungsten oxide as a potential alternative to the state-of-the-art platinum for hydrogen evolution.

CoSex nanocrystalline-dotted CoCo layered double hydroxide nanosheets: a synergetic engineering process for enhanced electrocatalytic water oxidation

Manipulating the electrical conductivity and morphology of Co-based (hydr)oxides is significant for optimizing energy conversion in the oxygen evolution reaction (OER). Herein, 2D CoSe_x nanocrystalline-dotted porous CoCo layered double hydroxide nanosheets (Co-Se NSs) were designed and synthesized via a modified in situ reduction and interface-directed assembly in an inert atmosphere. During the synchronous reduction/precipitation reaction between Co²⁺-oleylamine and NaHSe at the toluene-water interface, the hydrated Co-O and Co-Se clusters are generated and sequentially assemble under strong extrusion driven by the interfacial tension. Owing to the enriched vacancies on the lateral surfaces, the obtained loose and porous Co-Se NS presents low crystallinity. Moreover, electrons could spontaneously transfer from the CoCo LDH to the neighboring CoSe_x nanocrystallites due to the stronger electron-withdrawing capability of metallic CoSe_x, and thus more Co atoms in the CoCo layered double hydroxide (LDH) present a high oxidation state. This synergistic manipulation in the structure, component, and electron configuration of the Co-Se NS can increase the density of the OER active-sites, improve the electrical conductivity, and also offer a large accessible surface area and permeable channels for ion adsorption and transport. As a result, the resulting Co-Se NSs feature high catalytic activity towards OER, in particular a low onset potential of 1.48 V and an overpotential of only 290 mV at a current density of 10 mA cm^-2 for the Co-Se-2 NS, as well as good stability in an accelerated durability test. The strategy developed here provides a reliable and valid way to synthesize multicomponent NSs, and is able to be extended to other areas of application.

Architecting a Mesoporous N-Doped Graphitic Carbon Framework Encapsulating CoTe2 as an Efficient Oxygen Evolution Electrocatalyst

To improve the efficiency of cobalt-based catalysts for water electrolysis, tremendous efforts have been dedicated to tuning the composition, morphology, size, and structure of the materials. We report here a facile preparation of orthorhombic CoTe₂ nanocrystals embedded in an N-doped graphitic carbon matrix to form a 3D architecture with a size of ∼500 nm and abundant mesopores of ∼4 nm for the oxygen evolution reaction (OER). The hybrid electrocatalyst delivers a small overpotential of 300 mV at 10 mA cm^-2, which is much lower than that for pristine CoTe₂ powder. After cycling for 2000 cycles or driving continual OER for 20 h, only a slight loss is observed. The mesoporous 3D architecture and the strong interaction between N-doped graphitic carbon and CoTe₂ are responsible for the enhancement of the electrocatalytic performance.

Rational Design of Cobalt-Iron Selenides for Highly Efficient Electrochemical Water Oxidation

Exploring active, stable, earth-abundant, low-cost, and high-efficiency electrocatalysts is highly desired for large-scale industrial applications toward the low-carbon economy. In this study, we apply a versatile selenizing technology to synthesize Se-enriched Co_1-xFe_xSe₂ catalysts on nickel foams for oxygen evolution reactions (OERs) and disclose the relationship between the electronic structures of Co_1-xFe_xSe₂ (via regulating the atom ratio of Co/Fe) and their OER performance. Owing to the fact that the electron configuration of the Co_1-xFe_xSe₂ compounds can be tuned by the incorporated Fe species (electron transfer and lattice distortion), the catalytic activity can be adjusted according to the Co/Fe ratios in the catalyst. Moreover, the morphology of Co_1-xFe_xSe₂ is also verified to strongly depend on the Co/Fe ratios, and the thinner Co_0.4Fe_0.6Se₂ nanosheets are obtained upon selenization treatment, in which it allows more active sites to be exposed to the electrolyte, in turn promoting the OER performance. The Co_0.4Fe_0.6Se₂ nanosheets not only exhibit superior OER performance with a low overpotential of 217 mV at 10 mA cm^-2 and a small Tafel slope of 41 mV dec^-1 but also possess ultrahigh durability with a dinky degeneration of 4.4% even after 72 h fierce water oxidation test in alkaline solution, which outperforms the commercial RuO₂ catalyst. As expected, the Co_0.4Fe_0.6Se₂ nanosheets have shown great prospects for practical applications toward water oxidation.

Pyrite-Type Nanomaterials for Advanced Electrocatalysis

Since being proposed by John Bockris in 1970, hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy. Access to reliable and affordable hydrogen economy, however, requires cost-effective and highly efficient electrocatalytic materials that replace noble metals (e.g., Pt, Ir, Ru) to negotiate electrode processes such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). Although substantial advances in the development of inexpensive catalysts, successful deployment of these materials in fuel cells and electrolyzers will depend on their improved activity and robustness. Recent research has demonstrated that the nanostructuring of Earth-abundant minerals provides access to newly advanced energy materials, particularly for nanostructured pyrites, which are attracting great interest. Crystalline pyrites commonly contain the characteristic dianion units and have cations occurring in octahedral coordination-whose generalized formula is MX₂, where M can be transition metal of groups 8-12 and X is a chalcogen. The diversity of pyrites that are accessible and their versatile and tunable properties make them attractive for a wide range of applications from photovoltaics to energy storage and electrocatalysis. Pyrite-type structures can be further extended to their ternary analogues, for example, CoAsS (cobaltite), NiAsS (gersdorffite), NiSbS (ullmannite), CoPS, and many others. Moreover, improved properties of pyrites can be realized through grafting them with promoter objects (e.g., metal oxides, metal chalcogenides, noble metals, and carbons), which bring favorable interfaces and structural and electronic modulations, thus leading to performance gains. In recent years, research on the synthesis of pyrite nanomaterials and on related structure understanding has dramatically advanced their applications, which offers new perspectives in the search for efficient and robust electrocatalysts, yet a focused review that concentrates the critical developments is still missing. In this Account, we describe our recent progress on the discoveries and applications of nanostructured pyrite-type materials in the area of electrocatalysis. We first briefly highlight some interesting properties of pyrite-type materials and why they are attractive for modern electrocatalysis. Some recent advances on their synthesis that allows access to highly nanostructured pyrite-type materials are reviewed, along with the grafting of resultant pyrites with foreign materials (e.g., metal oxides, metal chalcogenides, noble metals, and carbons) to enable improved catalytic performances. We finally spotlight the exciting examples where pyrite nanostructures were used as efficient electrocatalysts to drive the OER, HER, and methanol-tolerant ORR. It is reasonable to assume that, with significant efforts and focus, the next few years will bring new advances on the pyrites and other minerals for electrocatalysis.

3D Nitrogen-Anion-Decorated Nickel Sulfides for Highly Efficient Overall Water Splitting

Developing non-noble-metal electrocatalysts with high activity and low cost for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is of paramount importance for improving the generation of H₂ fuel by electrocatalytic water-splitting. This study puts forward a new N-anion-decorated Ni₃ S₂ material synthesized by a simple one-step calcination route, acting as a superior bifunctional electrocatalyst for the OER/HER for the first time. The introduction of N anions significantly modifies the morphology and electronic structure of Ni₃ S₂ , bringing high surface active sites exposure, enhanced electrical conductivity, optimal HER Gibbs free-energy (ΔG_H* ), and water adsorption energy change (ΔG_H2O* ). Remarkably, the obtained N-Ni₃ S₂ /NF 3D electrode exhibits extremely low overpotentials of 330 and 110 mV to reach a current density of 100 and 10 mA cm^-2 for the OER and HER in 1.0 m KOH, respectively. Moreover, an overall water-splitting device comprising this electrode delivers a current density of 10 mA cm^-2 at a very low cell voltage of 1.48 V. Our finding introduces a new way to design advanced bifunctional catalysts for water splitting.

Molybdenum Disulfide-Black Phosphorus Hybrid Nanosheets as a Superior Catalyst for Electrochemical Hydrogen Evolution

Engineering electronic properties is a promising way to design nonprecious-metal or earth-abundant catalysts toward hydrogen evolution reaction (HER). Herein, we deposited catalytically active MoS₂ flakes onto black phosphorus (BP) nanosheets to construct the MoS₂-BP interfaces. In this case, electrons flew from BP to MoS₂ in MoS₂-BP nanosheets because of the higher Fermi level of BP than that of MoS₂. MoS₂-BP nanosheets exhibited remarkable HER performance with an overpotential of 85 mV at 10 mA cm^-2. Due to the electron donation from BP to MoS₂, the exchange current density of MoS₂-BP reached 0.66 mA cm^-2, which was 22 times higher than that of MoS₂. In addition, both the consecutive cyclic voltammetry and potentiostatic tests revealed the outstanding electrocatalytic stability of MoS₂-BP nanosheets. Our finding not only provides a superior HER catalyst, but also presents a straightforward strategy to design hybrid electrocatalysts.