Surface Engineering of MoS2 via Laser‐Induced Exfoliation in Protic Solvents

With excellent performance in the hydrogen evolution reaction (HER), molybdenum disulfide (MoS₂) is considered a promising nonprecious candidate to substitute Pt‐based catalysts. Herein, pulsed laser irradiation in liquid is used to realize one‐step exfoliation of bulk 2H‐MoS₂ to ultrastable few‐layer MoS₂ nanosheets. Such prepared MoS₂ nanosheets are rich in S vacancies and metallic 1T phase, which significantly contribute to the boosted catalytic HER activity. Protic solvents play a pivotal role in the production of S vacancies and 2H‐to‐1T phase transition under laser irradiation. MoS₂ exfoliated in an optimal solvent of formic acid exhibits outstanding HER activity with an overpotential of 180 mV at 10 mA cm^?2 and Tafel slope of 54 mV dec^?1.     

Nickel@Nitrogen‐Doped Carbon@MoS2 Nanosheets: An Efficient Electrocatalyst for Hydrogen Evolution Reaction

Developing cheap, abundant, and easily available electrocatalysts to drive the hydrogen evolution reaction (HER) at small overpotentials is an urgent demand of hydrogen production from water splitting. Molybdenum disulfide (MoS₂) based composites have emerged as competitive electrocatalysts for HER in recent years. Herein, nickel@nitrogen‐doped carbon@MoS₂ nanosheets (Ni@NC@MoS₂) hybrid sub‐microspheres are presented as HER catalyst. MoS₂ nanosheets with expanded interlayer spacings are vertically grown on nickel@nitrogen‐doped carbon (Ni@NC) substrate to form Ni@NC@MoS₂ hierarchical sub‐microspheres by a simple hydrothermal process. The formed Ni@NC@MoS₂ composites display excellent electrocatalytic activity for HER with an onset overpotential of 18 mV, a low overpotential of 82 mV at 10 mA cm^?2, a small Tafel slope of 47.5 mV dec^?1, and high durability in 0.5 H₂SO₄ solution. The outstanding HER performance of the Ni@NC@MoS₂ catalyst can be ascribed to the synergistic effect of dense catalytic sites on MoS₂ nanosheets with exposed edges and expanded interlayer spacings, and the rapid electron transfer from Ni@NC substrate to MoS₂ nanosheets. The excellent Ni@NC@MoS₂ electrocatalyst promises potential application in practical hydrogen production, and the strategy reported here can also be extended to grow MoS₂ on other nitrogen‐doped carbon encapsulated metal species for various applications.     

3D 1T‐MoS2/CoS2 Heterostructure via Interface Engineering for Ultrafast Hydrogen Evolution Reaction

Metallic phase (1T) MoS₂ has been regarded as an appealing material for hydrogen evolution reaction. In this work, a novel interface‐induced strategy is reported to achieve stable and high‐percentage 1T MoS₂ through highly active 1T‐MoS₂/CoS₂ hetero‐nanostructure. Herein, a large number of heterointerfaces can be obtained by interlinked 1T‐MoS₂ and CoS₂ nanosheets in situ grown from the molybdate cobalt oxide nanorod under moderate conditions. Owing to the strong interaction between MoS₂ and CoS₂, high‐percentage of metallic‐phase (1T) MoS₂ of 76.6% can be achieved, leading to high electroconductivity and abundant active sites compared to 2H MoS₂. Furthermore, the interlinked MoS₂ and CoS₂ nanosheets can effectively disperse the nanosheets so as to enlarge the exposed active surface area. The near zero free energy of hydrogen adsorption at the heterointerface can also be achieved, indicating the fast kinetics and excellent catalytic activity induced by heterojunction. Therefore, when applied in hydrogen evolution reaction (HER), 1T‐MoS₂/CoS₂ heterostructure delivers low overpotential of 71 and 26 mV at the current density of 10 mA cm^?2 with low Tafel slops of 60 and 43 mV dec^?1, respectively in alkaline and acidic conditions.     

Structure Engineering of MoS2 via Simultaneous Oxygen and Phosphorus Incorporation for Improved Hydrogen Evolution

Oxygen and phosphorus dual‐doped MoS₂ nanosheets (O,P‐MoS₂) with porous structure and continuous conductive network are fabricated using a one‐pot NaH₂PO₂‐assisted hydrothermal approach. By simply changing the precursor solution, the chemical composition and resulting structure can be effectively controlled to obtain desired properties toward the hydrogen evolution reaction (HER). Thanks to the beneficial structure and strong synergistic effects between the incorporated oxygen and phosphorus, the optimal O,P‐MoS₂ exhibit superior electrocatalytic performances compared with those of oxygen single‐doped MoS₂ nanosheets (O‐MoS₂). Specifically, a low HER onset overpotential of 150 mV with a small Tafel slope of 53 mV dec^?1, excellent conductivity, and long‐term durability are achieved by the structural engineering of MoS₂ via O and P co‐doping, making it an efficient HER electrocatalyst for water electrocatalysis. This work provides an alternative strategy to manipulate transition metal dichalcogenides as advanced materials for electrocatalytic and related energy applications.     

Coupling Interface Constructions of MoS2/Fe5Ni4S8 Heterostructures for Efficient Electrochemical Water Splitting

Water splitting is considered as a pollution‐free and efficient solution to produce hydrogen energy. Low‐cost and efficient electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are needed. Recently, chemical vapor deposition is used as an effective approach to gain high‐quality MoS₂ nanosheets (NSs), which possess excellent performance for water splitting comparable to platinum. Herein, MoS₂ NSs grown vertically on FeNi substrates are obtained with in situ growth of Fe₅Ni₄S₈ (FNS) at the interface during the synthesis of MoS₂. The synthesized MoS₂/FNS/FeNi foam exhibits only 120 mV at 10 mA cm^?2 for HER and exceptionally low overpotential of 204 mV to attain the same current density for OER. Density functional theory calculations further reveal that the constructed coupling interface between MoS₂ and FNS facilitates the absorption of H atoms and OH groups, consequently enhancing the performances of HER and OER. Such impressive performances herald that the unique structure provides an approach for designing advanced electrocatalysts.     

Flexible Honeycombed Nanoporous/Glassy Hybrid for Efficient Electrocatalytic Hydrogen Generation

Hydrogen evolution reaction (HER) in alkaline media urgently requires electrocatalysts concurrently possessing excellent activity, flexible free‐standing capability, and low cost. A honeycombed nanoporous/glassy sandwich structure fabricated through dealloying metallic glass (MG) is reported. This free‐standing hybrid shows outstanding HER performance with a very small overpotential of 37 mV at 10 mA cm^?2 and a low Tafel slope of 30 mV dec^?1 in alkaline media, outperforming commercial Pt/C. By alloying 3 at% Pt into the MG precursor, a honeycombed Pt₇₅Ni₂₅ solid solution nanoporous structure, with fertile active sites and large contact areas for efficient HER, is created on the dealloyed MG surface. Meanwhile, the surface compressive lattice‐strain effect is also introduced by substituting the Pt lattice sites with the smaller Ni atoms, which can effectively reduce the hydrogen adsorption energy and thus improve the hydrogen evolution. Moreover, the outstanding stability and flexibility stemming from the ductile MG matrix also make the hybrid suitable for practical electrode application. This work not only offers a reliable strategy to develop cost‐effective and flexible multicomponent catalysts with low Pt usage for efficient HER, but also sheds light on understanding the alloying effects of the catalytic process.     

Ruthenium Nanoparticles on Cobalt‐Doped 1T′ Phase MoS2 Nanosheets for Overall Water Splitting

2D MoS₂ nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co–Ru–MoS₂ hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T′ phase MoS₂ nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles. The catalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is characterized by low overpotentials of 52 and 308 mV at 10 mA cm^?2 and Tafel slopes of 55 and 50 mV decade^?1 in 1.0 m KOH, respectively. Analysis of X‐ray photoelectron and absorption spectra of the catalysts show that the MoS₂ well retained its metallic 1T′ phase, which guarantees good electrical conductivity during the reaction. The Gibbs free energy calculation for the reaction pathway in alkaline electrolyte confirms that the Ru nanoparticles on the Co‐doped MoS₂ greatly enhance the HER activity. Water adsorption and dissociation take place favorably on the Ru, and the doped Co further catalyzes HER by making the reaction intermediates more favorable. The high OER performance is attributed to the catalytically active RuO₂ nanoparticles that are produced via oxidation of Ru nanoparticles.     

Synergistic Phase and Disorder Engineering in 1T‐MoSe2 Nanosheets for Enhanced Hydrogen‐Evolution Reaction

MoSe₂ is a promising earth‐abundant electrocatalyst for the hydrogen‐evolution reaction (HER), even though it has received much less attention among the layered dichalcogenide (MX₂) materials than MoS₂ so far. Here, a novel hydrothermal‐synthesis strategy is presented to achieve simultaneous and synergistic modulation of crystal phase and disorder in partially crystallized 1T‐MoSe₂ nanosheets to dramatically enhance their HER catalytic activity. Careful structural characterization and defect characterization using positron annihilation lifetime spectroscopy correlated with electrochemical measurements show that the formation of the 1T phase under a large excess of the NaBH₄ reductant during synthesis can effectively improve the intrinsic activity and conductivity, and the disordered structure from a lower reaction temperature can provide abundant unsaturated defects as active sites. Such synergistic effects lead to superior HER catalytic activity with an overpotential of 152 mV versus reversible hydrogen electrode (RHE) for the electrocatalytic current density of j = ?10 mA cm^?2, and a Tafel slope of 52 mV dec^?1. This work paves a new pathway for improving the catalytic activity of MoSe₂ and generally MX₂‐based electrocatalysts via a synergistic modulation strategy.     

Carbon‐Encapsulated WOx Hybrids as Efficient Catalysts for Hydrogen Evolution

Developing non‐noble metal catalysts as Pt substitutes, with good activity and stability, remains a great challenge for cost‐effective electrochemical evolution of hydrogen. Herein, carbon‐encapsulated WO_x anchored on a carbon support (WO_x@C/C) that has remarkable Pt‐like catalytic behavior for the hydrogen evolution reaction (HER) is reported. Theoretical calculations reveal that carbon encapsulation improves the conductivity, acting as an electron acceptor/donor, and also modifies the Gibbs free energy of H* values for different adsorption sites (carbon atoms over the W atom, O atom, W? O bond, and hollow sites). Experimental results confirm that WO_x@C/C obtained at 900 °C with 40 wt% metal loading has excellent HER activity regarding its Tafel slope and overpotential at 10 and 60 mA cm^?2, and also has outstanding stability at ?50 mV for 18 h. Overall, the results and facile synthesis method offer an exciting avenue for the design of cost‐effective catalysts for scalable hydrogen generation.     

Sandwich‐like MoS2@SnO2@C with High Capacity and Stability for Sodium/Potassium Ion Batteries

Sandwich‐like MoS₂@SnO₂@C nanosheets are prepared by facile hydrothermal reactions. SnO₂ nanosheets can attach to exfoliated MoS₂ nanosheets to prevent restacking of adjacent MoS₂ nanosheets, and carbon transformed from polyvinylpyrrolidone is coated on MoS₂@SnO₂, forming a sandwich structure to maintain cycling stability. As an anode for sodium‐ion batteries, the electrode greatly deliverers a high initial discharge specific capacity of 530 mA h g^?1 and maintains at 396 mA h g^?1 after 150 cycles at 0.1 A g^?1. Even at a large current density of 1 A g^?1, it can hold 230 mA h g^?1 after 450 cycles. Besides, as an anode for K⁺ storage, the electrode also shows a discharge capacity of 312 mA h g^?1 after 25 cycles at 0.05 A g^?1. This work may provide a new strategy to prepare other composites which can be applied to new kind of rechargeable batteries.     

High Edge Selectivity of In Situ Electrochemical Pt Deposition on Edge‐Rich Layered WS2 Nanosheets

Recent studies show that the Pt electrode can be slowly dissolved into the acidic media and regenerate on the working electrode along with the long‐time hydrogen evolution reaction (HER) test. However, to date, the relationship between the Pt deposition and the intrinsic properties of the working electrode remains elusive. Herein, for the first time, the edge selectivity of in situ electrochemical Pt deposition on layered 2H‐WS₂ nanosheets, whose edge surface with rich dangling bonds is chemically active to regulate their properties, especially the interfacial reaction occurring between the electrode surface and the adjacent thin layer of the solution, is theoretically elucidated and experimentally verified by controlling the cathode polarization test using Pt wire as the counter electrode in H₂SO₄ solution. It is revealed that the layered WS₂ nanosheets with rich exposed edges show much stronger interaction with Pt atoms because the terminated S₂^2? or S^2? ligands on the edge exhibit much lower binding energy for Pt atoms compared with the apical S^2? ligands on the terrace surface. The in situ electrochemical Pt‐deposited WS₂ nanosheets with rich exposed edges can act as a highly active hybrid electrocatalyst to accelerate HER kinetics and exhibit commercial Pt‐like HER performance, especially in the alkaline media.     

Strong Coupling of MoS2 Nanosheets and Nitrogen‐Doped Graphene for High‐Performance Pseudocapacitance Lithium Storage

Layered material MoS₂ is widely applied as a promising anode for lithium‐ion batteries (LIBs). Herein, a scalable and facile dopamine‐assisted hydrothermal technique for the preparation of strongly coupled MoS₂ nanosheets and nitrogen‐doped graphene (MoS₂/N‐G) composite is developed. In this composite, the interconnected MoS₂ nanosheets are well wrapped onto the surface of graphene, forming a unique veil‐like architecture. Experimental results indicate that dopamine plays multiple roles in the synthesis: a binding agent to anchor and uniformly disperse MoS₂ nanosheets, a morphology promoter, and the precursor for in situ nitrogen doping during the self‐polymerization process. Density functional theory calculations further reveal that a strong interaction exists at the interface of MoS₂ nanosheets and nitrogen‐doped graphene, which facilitates the charge transfer in the hybrid system. When used as the anode for LIBs, the resulting MoS₂/N‐G composite electrode exhibits much higher and more stable Li‐ion storage capacity (e.g., 1102 mAh g^?1 at 100 mA g^?1) than that of MoS₂/G electrode without employing the dopamine linker. Significantly, it is also identified that the thin MoS₂ nanosheets display outstanding high‐rate capability due to surface‐dominated pseudocapacitance contribution.     

Intrinsic Ferromagnetism in Mn‐Substituted MoS2 Nanosheets Achieved by Supercritical Hydrothermal Reaction

Doping atomically thick nanosheets is a great challenge due to the self‐purification effect that drives the precipitation of dopants. Here, a breakthrough is made to dope Mn atoms substitutionally into MoS₂ nanosheets in a sulfur‐rich supercritical hydrothermal reaction environment, where the formation energy of Mn substituting for Mo sites in MoS₂ is significantly reduced to overcome the self‐purification effect. The substitutional Mn doping is convincingly evidenced by high‐angle annular dark‐field scanning transmission electron microscopy and X‐ray absorption fine spectroscopy characterizations. The Mn‐doped MoS₂ nanosheets show robust intrinsic ferromagnetic response with a saturation magnetic moment of 0.05 µ _B Mn^?1 at room temperature. The intrinsic ferromagnetism is further confirmed by the reversibility of the magnetic behavior during the cycle of incorporating/removing Li codopants, showing the critical role of Mn 3d electronic states in mediating the magnetic interactions in MoS₂ nanosheets.     

Interface Modulation of MoS2/Metal Oxide Heterostructures for Efficient Hydrogen Evolution Electrocatalysis

Developing efficient earth‐abundant MoS₂ based hydrogen evolution reaction (HER) electrocatalysts is important but challenging due to the sluggish kinetics in alkaline media. Herein, a strategy to fabricate a high‐performance MoS₂ based HER electrocatalyst by modulating interface electronic structure via metal oxides is developed. All the heterostructure catalysts present significant improvement of HER electrocatalytic activities, demonstrating a positive role of metal oxides decoration in promoting the rate‐limited water dissociation step for the HER mechanism in alkaline media. The as‐obtained MoS₂/Ni₂O₃H catalyst exhibits a low overpotential of 84 mV at 10 mA cm^?2 and small charge‐transfer resistance of 1.5 Ω in 1 m KOH solution. The current density (217 mA cm^?2) at the overpotential of 200 mV is about 2 and 24 times higher than that of commercial Pt/C and bare MoS₂, respectively. Additionally, these MoS₂/metal oxides heterostructure catalysts show outstanding long‐term stability under a harsh chronopotentiometry test. Theoretical calculations reveal the varied sensitivity of 3d‐band in different transition oxides, in which Ni‐3d of Ni₂O₃H is evidently activated to achieve fast electron transfer for HER as the electron‐depletion center. Both electronic properties and energetic reaction trends confirm the high electroactivity of MoS₂/Ni₂O₃H in the adsorption and dissociation of H₂O for highly efficient HER in alkaline media.     

Engineering 2D Metal–Organic Framework/MoS2 Interface for Enhanced Alkaline Hydrogen Evolution

2D metal–organic frameworks (MOFs) have been widely investigated for electrocatalysis because of their unique characteristics such as large specific surface area, tunable structures, and enhanced conductivity. However, most of the works are focused on oxygen evolution reaction. There are very limited numbers of reports on MOFs for hydrogen evolution reaction (HER), and generally these reported MOFs suffer from unsatisfactory HER activities. In this contribution, novel 2D Co‐BDC/MoS₂ (BDC stands for 1,4‐benzenedicarboxylate, C₈H₄O₄) hybrid nanosheets are synthesized via a facile sonication‐assisted solution strategy. The introduction of Co‐BDC induces a partial phase transfer from semiconducting 2H‐MoS₂ to metallic 1T‐MoS₂. Compared with 2H‐MoS₂, 1T‐MoS₂ can activate the inert basal plane to provide more catalytic active sites, which contributes significantly to improving HER activity. The well‐designed Co‐BDC/MoS₂ interface is vital for alkaline HER, as Co‐BDC makes it possible to speed up the sluggish water dissociation (rate‐limiting step for alkaline HER), and modified MoS₂ is favorable for the subsequent hydrogen generation step. As expected, the resultant 2D Co‐BDC/MoS₂ hybrid nanosheets demonstrate remarkable catalytic activity and good stability toward alkaline HER, outperforming those of bare Co‐BDC, MoS₂, and almost all the previously reported MOF‐based electrocatalysts.     

Rational Design of Atomic Layers of Pt Anchored on Mo2C Nanorods for Efficient Hydrogen Evolution over a Wide pH Range

Transition metal carbide compound has been extensively investigated as a catalyst for hydrogenation, for example, due to its noble metal‐like properties. Herein a facile synthetic strategy is applied to control the thickness of atomic‐layer Pt clusters strongly anchored on N‐doped Mo₂C nanorods (Pt/N‐Mo₂C) and it is found that the Pt atomic layers modify Mo₂C function as a high‐performance and robust catalyst for hydrogen evolution. The optimized 1.08 wt% Pt/N‐Mo₂C exhibits 25‐fold, 10‐fold, and 15‐fold better mass activity than the benchmark 20 wt% Pt/C in neutral, acidic, and alkaline media, respectively. This catalyst also represents an extremely low overpotential of ?8.3 mV at current density of 10 mA cm^?2, much better than the majority of reported electrocatalysts and even the commercial reference catalyst (20 wt%) Pt/C. Furthermore, it exhibits an outstanding long‐term operational durability of 120 h. Theoretical calculation predicts that the ultrathin layer of Pt clusters on Mo‐Mo₂C yields the lowest absolute value of ΔG_H*. Experimental results demonstrate that the atomic layer of Pt clusters anchored on Mo₂C substrate greatly enhances electron and mass transportation efficiency and structural stability. These findings could provide the foundation for developing highly effective and scalable hydrogen evolution catalysts.     

Ultrasmall Fe3O4 Nanoparticle/MoS2 Nanosheet Composites with Superior Performances for Lithium Ion Batteries

A novel composite consisting of graphene‐like MoS₂ nanosheets and ultrasmall Fe₃O₄ nanoparticles (≈3.5 nm) is synthesized as an anode for lithium ion battery application. In such composite anode, MoS₂ nanosheets provide flexible substrates for the nanoparticle decoration, accommodating the volume changes of Fe₃O₄ during cycling process; while Fe₃O₄ nanoparticles primarily act as spacers to stabilize the composite structure, making the active surfaces of MoS₂ nanosheets accessible for electrolyte penetration during charge/discharge processes. Owing to the high reversible capacity provided by the MoS₂ nanosheets and the superior high rate performance offered by ultrasmall Fe₃O₄ nanoparticles, superior cyclic and rate performances are achieved by Fe₃O₄/MoS₂ anode during the subsequent electrochemical tests, delivering 1033 and 224 mAh g^?1 at current densities of 2000 and 10 000 mA g^?1, respectively.     

Superior Hydrogen Evolution Reaction Performance in 2H‐MoS2 to that of 1T Phase

In the hydrogen evolution reaction (HER), energy‐level matching is a prerequisite for excellent electrocatalytic activity. Conventional strategies such as chemical doping and the incorporation of defects underscore the complicated process of controlling the doping species and the defect concentration, which obstructs the understanding of the function of band structure in HER catalysis. Accordingly, 2H‐MoS₂ and 1T‐MoS₂ are used to create electrocatalytic nanodevices to address the function of band structure in HER catalysis. Interestingly, it is found that the 2H‐MoS₂ with modulated Fermi level under the application of a vertical electric field exhibits excellent electrocatalytic activity (as evidenced by an overpotential of 74 mV at 10 mA cm^?2 and a Tafel slope of 99 mV per decade), which is superior to 1T‐MoS₂. This unexpected excellent HER performance is ascribed to the fact that electrons are injected into the conduction band under the condition of back‐gate voltage, which leads to the increased Fermi level of 2H‐MoS₂ and a shorter Debye screen length. Hence, the required energy to drive electrons from the electrocatalyst surface to reactant will decrease, which activates the 2H‐MoS₂ thermodynamically.     

Phosphorus‐Rich Colloidal Cobalt Diphosphide (CoP2) Nanocrystals for Electrochemical and Photoelectrochemical Hydrogen Evolution

Developing earth‐abundant and efficient electrocatalysts for photoelectrochemical water splitting is critical to realizing a high‐performance solar‐to‐hydrogen energy conversion process. Herein, phosphorus‐rich colloidal cobalt diphosphide nanocrystals (CoP₂ NCs) are synthesized via hot injection. The CoP₂ NCs show a Pt‐like hydrogen evolution reaction (HER) electrocatalytic activity in acidic solution with a small overpotential of 39 mV to achieve ?10 mA cm^?2 and a very low Tafel slope of 32 mV dec^?1. Density functional theory (DFT) calculations reveal that the high P content both physically separates Co atoms to prevent H from over binding to multiple Co atoms, while simultaneously stabilizing H adsorbed to single Co atoms. The catalytic performance of the CoP₂ NCs is further demonstrated in a metal–insulator–semiconductor photoelectrochemical device consisting of bottom p‐Si light absorber, atomic layer deposition Al–ZnO passivation layers, and the CoP₂ cocatalyst. The p‐Si/AZO/TiO₂/CoP₂ photocathode shows a photocurrent density of ?16.7 mA cm^?2 at 0 V versus reversible hydrogen electrode (RHE) and an output photovoltage of 0.54 V. The high performance and stability are attributed to the junction between p‐Si and AZO, the corrosion‐resistance of the pinhole‐free TiO₂ protective layer, and the fast HER kinetics of the CoP₂ NCs.     

Urea-assisted synthesis of amorphous molybdenum sulfide on P-doped carbon nanotubes for enhanced hydrogen evolution

Amorphous molybdenum sulfide on P-doped carbon nanotubes (MoS _x /P-CNTs) composite with an original leaves–branch architecture for hydrogen evolution reaction (HER) is successfully fabricated by urea-assisted synthesis via a facile hydrothermal process. It is found that urea used in the process of preparation played a crucial role in the establishment of this unique structure, where leaves-like MoS _x nanosheets are uniformly anchored on P-CNTs substrate. Besides, the optimal amount of MoS _x on P-CNTs bundles is investigated in this paper. Due to the synergistic coupling effects of MoS _x nanosheets and P-CNTs bundles, as a result, the unique structure maintains abundant active sites, a high electrical conductivity as well as distinctive electrons transport mechanism, which gives the optimum MoS _x /P-CNTs composite, a higher activity for HER with an overpotential of 151 mV (vs. RHE) to reach a current density of 10 mA cm^?2 and a smaller Tafel slope of 49 mV dec^?1. Stability tests indicate that the catalyst exhibits excellent electrochemical durability in 0.5 M H₂SO₄ solution. We envision that this work could provide new insights into the rational design of MoS _x -based electrocatalysts for energy conversion and storage.