Three-dimensional ZnCo/MoS2–Co3S4/NF heterostructure supported on nickel foam as highly efficient catalyst for hydrogen evolution reaction

Exploring inexpensive and earth-abundant electrocatalysts for hydrogen evolution reactions is crucial in electrochemical sustainable chemistry field. In this work, a high-efficiency and inexpensive non-noble metal catalysts as alternatives to hydrogen evolution reaction (HER) was designed by one-step hydrothermal and two-step electrodeposition method. The as-prepared catalyst is composed of the synergistic MoS₂–Co₃S₄ layer decorated by ZnCo layered double hydroxides (ZnCo-LDH), which forms a multi-layer heterostructure (ZnCo/MoS₂–Co₃S₄/NF). The synthesized ZnCo/MoS₂–Co₃S₄/NF exhibits a small overpotential of 31 mV and a low Tafel plot of 53.13 mV dec^?1 at a current density of 10 mA cm^?2, which is close to the HER performance of the overpotential (26 mV) of Pt/C/NF. The synthesized ZnCo/MoS₂–Co₃S₄/NF also has good stability in alkaline solution. The excellent electrochemical performance of ZnCo/MoS₂–Co₃S₄/NF electrode originates from its abundant active sites and good electronic conductivity brought by the multilayer heterostructure. This work provides a simple and feasible way to design alkaline HER electrocatalysts by growing heterostructures on macroscopic substrates.     

Synthesis of Ni2P/Ni5P4 on porous N decorated rGO foam for efficiently electrocatalytic hydrogen evolution reaction

As a new generation of non-precious metal catalysts, nickel phosphide is regarded as an ideal substitute for precious metal platinum in electrochemical hydrogen evolution. Here, a hydrogen evolution reaction (HER) electrocatalyst is developed by in situ growth of Ni₂P/Ni₅P₄ heterostructures on porous N decorated rGO foam (named Ni₂P/Ni₅P₄/N-rGO). The porous rGO foam structure provides a larger surface area and abundant active sites. The Ni₂P/Ni₅P₄ nanoparticles with heterostructures are uniformly distributed on the rGO sheet, which enhance the charge transfer ability. The decorating of N element also correspondingly improves the HER performance. The as-prepared Ni₂P/Ni₅P₄/N-rGO exhibits excellent HER performance in alkaline medium. When the current density is 10 mA cm^?2, the overpotential is only 22 mV. No obvious loss of HER activity after 2000 cyclic voltammetry indicates that the composite has excellent stability. This work presents a valuable route for fabricating inexpensive and high-performance catalysts for electrocatalysis.     

Phosphorus-doping induced electronic modulation of CoS2–MoS2 hollow spheres on MoO2 film-Mo foil for synergistically boosting alkaline hydrogen evolution reaction

Combination of anionic doping and multicomponent synergism are effective approach to improve the performance of electrocatalysts toward hydrogen evolution reaction (HER) process. Herein, P-doped CoS₂–MoS₂ hollow spheres assembled by countless sheets on oxidized Mo foil (P–CoS₂/MoS₂/MoO₂) was synthesized by hydrothermal and phosphorization process. The unique hollow structure with countless sheets as wall endows more accessible active sites, fast electron/mass transport and high conductivity. P-doping could redistribute the local charge density and optimize the surface charge state to improve the intrinsic activity and accelerate reaction kinetics. The optimized P–CoS₂/MoS₂/MoO₂ exhibits an outstanding HER performance with an overpotential of 85 mV to reach 10 mA cm⁻², a small Tafel slope of 84.6 mV dec⁻¹, superior intrinsic HER activity and robust durability under alkaline solution. This work proposed a feasible strategy to build the hollow, heterostructured and binder-free electrode in renewable energy application.     

Boosting electrochemical hydrogen evolution activity of MoS2 nanosheets via facile decoration of Au overlayer

--Owing to its unique physicochemical properties, two-dimensional (2D) layered MoS₂ has been proposed as a potential catalyst for efficient hydrogen evolution reaction (HER). However, their large-scale application is still hindered due to limited active sites, poor conductivity, and restacking during synthesis. Herein, we report a one-step hydrothermal route to grow MoS₂ nanosheets on molybdenum (Mo) foil substrate followed by Au decoration as an active cocatalyst to enhance the HER performance of MoS₂ nanosheets. A facile, quick, and controlled decoration of stable Au overlayer with different mass loadings was performed using a sputtering Au coating unit for different deposition times (10s, 30s, and 50s), thus paving the way for producing efficient and inexpensive HER electrocatalysts. Electrochemical studies of different Au–MoS₂/Mo hybrids demonstrate that the optimized Au–MoS₂/Mo-30s sample exhibits ultralow onset potential (52 ± 2 mV vs. RHE), small overpotentials of 136 ± 6 and 318 ± 3 mV (vs. RHE) at current densities of 10 and 100 mA cm^?2, a small Tafel slope (46.23 ± 6 mV/dec), along with an outstanding electrochemical stability over a couple of days. Presence of metallic 1T-phase of MoS₂, as well as the synergistic effect between MoS₂ and Au, result in enhanced electrical conductivity, high density of active sites, large electrochemically accessible surface area, and fast charge transfer at the catalyst-electrolyte interface for boosting HER activity of the hybrid catalyst.     

Nanostructural Co–MoS2/NiCoS supported on reduced Graphene oxide as a high activity electrocatalyst for hydrogen evolution in alkaline media

There are many tremendous challenges to enhance the hydrogen evolution reaction (HER) activity of MoS₂. In this study, nanoflower-like Co–MoS₂/NiCoS structure supported on reduced Graphene Oxide (rGO) was rationally developed via a simple hydrothermal route, where the synergistic regulations of both interface structural and electronic conductivity were successfully presented by using controllable interface engineering and Co metal ions doped into MoS₂ nanosheets. Ascribed to the 3D flower-like nanostructure with massive active sites, the interface coupling effect between MoS₂ and Ni–Co–S phase, and Co-doped MoS₂ can modulate its surface electronic density. The optimal Co–MoS₂/NiCoS/rGO hybrid exhibits excellent HER activity in 1.0 M KOH, with a small overpotential (η₁₀, 84 mV) at 10 mA cm^?2 and a low Tafel slope (46 mV dec^?1), accompanied by good stability. This work provides an effective route to produce other electrocatalysts based on interface structure and electronic conductivity engineering for HER in the future.     

Carbon dots modified molybdenum disulfide as a high-efficiency hydrogen evolution electrocatalyst

Molybdenum disulfide (MoS₂) is considered a low-cost material that may replace platinum-based electrocatalysts towards hydrogen evolution reaction (HER). However, the catalytic activity of MoS₂ is limited by the low conductivity and lack of active sites. Here, a biomass carbon dots-molybdenum disulfide (BCDs-MoS₂) composite was synthesized as a HER catalyst by a simple hydrothermal method. The BCDs-MoS₂ catalyst displayed excellent electrocatalytic performance for HER with lower onset overpotential (115 mV), smaller Tafel slope (56.57 mV dec^?1) as well as high cycling stability, which superior to those of homemade MoS₂, commercial MoS₂, and most of the reported MoS₂-based catalysts. According to the characterization results of morphology, surface properties, and valence states of elements, the outstanding catalytic activity of BCDs-MoS₂ is ascribed to its loose structure with a large specific surface area along with abundant edges and defects, and the increase in the amount of S₂^2? and S^2? which possess higher activity due to the addition of the BCDs. This study can afford a new strategy to design high performance HER catalysts.     

Advanced catalysts for hydrogen evolution reaction based on MoS2/NiCo2S4 heterostructures in Alkaline Media

There are great challenges to develop and fabricate a high performance, low-cost and stable non-platinum catalyst for hydrogen evolution reaction (HER). In our study, we firstly developed a simple method to successfully fabricate a new MoS₂/NiCo₂S₄ heterostructure by a two-step hydrothermal method, and studied the HER property of MoS₂/NiCo₂S₄, where the as-prepared NiCo-layered double hydroxide (NiCo-LDH) was used as the precursor of NiCo₂S₄. Benefitting from the prominent synergistic effect between NiCo₂S₄ and MoS₂, MoS₂ provided massive catalytic active edge sites, and NiCo₂S₄ enhanced the conductivity of the composite. As a result, the MoS₂/NiCo₂S₄ showed excellent HER catalytic activity, with a current of 10 mA cm⁻² at overpotential of 94 mV for HER and a low Tafel slope of 46 mV dec⁻¹, and good cycling stability in Alkaline Media. As well as, our work offered one promising high active and stable non-platinum catalyst for overall water splitting.     

Preparation of ultrathin molybdenum disulfide dispersed on graphene via cobalt doping: A bifunctional catalyst for hydrogen and oxygen evolution reaction

The development of highly active and low-cost catalysts for hydrogen evolution reaction (HER) is significant for the development of clean and renewable energy research. Owing to the low H adsorption free energy, molybdenum disulfide (MoS₂) is regarded as a promising candidate for HER, but it shows low activity for oxygen evolution reaction (OER). Herein, graphene-supported cobalt-doped ultrathin molybdenum disulfide (Co–MoS₂/rGO) was synthesized via a one-pot hydrothermal method. The obtained hybrids modified electrode exhibits a high HER catalytic activity with a low overpotential of 147 mV at the current density of 10 mA cm⁻², a small Tafel slope of 49.5 mV dec⁻¹, as well as good electrochemical stability in acidic electrolyte. Meanwhile, the catalyst shows remarkable OER activity with a low overpotential of 347 mV at 10 mA cm⁻². The superior activity is ascribed not only to the high conductivity originated from the reduced graphene, but also to the synergistic effect between MoS₂ and cobalt.     

Cu–MoS2/rGO hybrid material for enhanced hydrogen evolution reaction performance

Cu doped MoS₂ (Cu–MoS₂)/reduced graphene oxide (rGO) (Cu–MoS₂/rGO) hybrid material is fabricated by a facile one-step solvothermal method. The X-ray diffraction (XRD) results suggest that the doping of Cu does not alter the crystal structure of MoS₂. X-ray photoelectron spectroscopy (XPS) analysis reveal that the doping of Cu atoms influences the electronic structure of MoS₂, which is favorable to increase active sites of edges. Electrochemical impedance spectroscopy (EIS) results indicate that Cu–MoS₂/rGO performed a faster charge-transfer in comparison to MoS₂/rGO hybrid. In addition, the resultant Cu–MoS₂/rGO catalyst with Cu/Mo mole ratio of 9% exhibits a lower overpotential of 199 mV at 10 mA cm⁻², small Tafel slop of 44 mV dec⁻¹ and cycling stability, indicative of enhanced electrocatalytic activity towards HER. The improved performance is attributed to the increased active sites and a synergistic effect between copper and molybdenum, leading to electronic structure change and charge redistribution of MoS₂.     

Amorphous MoS2 nanosheets on MoO2 films/Mo foil as free-standing electrode for synergetic electrocatalytic hydrogen evolution reaction

A facile oxidation-sulfidation strategy is proposed to fabricate the vertically aligned amorphous MoS₂ nanosheets on MoO₂ films/Mo foil (MF) as free-standing electrode, which features as the integration of three merits (high conductivity, abundant exposures of active sites, and enhanced mass transfer) into one electrode for hydrogen evolution reaction (HER). Density functional theory (DFT) calculations reveal the strong interaction between MoS₂ and MoO₂, which can enhance the intrinsic conductivity with narrow bandgap, and decreases hydrogen adsorption free energy (ΔG_H1 = ~0.06 eV) to facilitate the HER process. Benefiting from the unique hierarchical structure with amorphous MoS₂ nanosheets on conductive MoO₂ films/MF to facilitate the electron/mass transfer by eliminate contact resistance, controllable number of stacking layers and size of MoS₂ slabs to expose more edge sites, the optimal MoS₂/MoO₂/MF exhibits outstanding activity with overpotential of 154 mV at the current density of 10 mA cm⁻², Tafel slope of 52.1 mV dec⁻¹, and robust stability. Furthermore, the intrinsic HER activity (vs. ECSA) on MoS₂/MoO₂/MF is significantly enhanced, which shows 4.5 and 18.6 times higher than those of MoS₂/MF and MoO₂/MF at overpotential of 200 mV, respectively.     

Heterostructure and phase engineering synergistically activated highly efficient alkaline hydrogen evolution in Mo2C/MoS2-rGO hybrids

Heterostructure and phase engineering are effective method to tune the electronic structure of MoS₂, which can activate and boost its intrinsic catalytic activity. Herein, the theoretical calculations reveal that the free energy of H1 adsorption (ΔG_H1) for Mo₂C (−0.65 eV) is lower than MoS₂ (2.05 eV), which is favorable for hydrogen adsorption. Inspired by the theoretical predictions, we develop a facile strategy to prepare nanostructured Mo₂C/MoS₂ dispersed on reduced graphene oxide (rGO) via a hydrothermal preparation and carburization reaction. Since the Mo₂C/MoS₂-rGO nanostructures with great deal of both MoS₂ and Mo₂C edges by heterostructure and phase engineering, which can induce massive active sites for HER on the surface of rGO, the intimate interfacial coupling effect between Mo₂C and MoS₂ can effectively improve the charge transfer rate. The Mo₂C/MoS₂-rGO catalyst exhibits exceptional HER properties, delivering a high turnover frequency (TOF) of 0.209 s⁻¹ at an overpotential of 200 mV in 0.1 M KOH. This work may open a new window for designing NPM electrocatalysts with highly efficient HER property based on earth-abundant materials.     

N-doped carbon wrapped CoFe alloy nanoparticles with MoS2 nanosheets as electrocatalyst for hydrogen and oxygen evolution reactions

Developing efficient and cost-effective transition metal-based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial to generate clean and renewable hydrogen energy. The construction of hybrid catalysts with multiple active sites is an effective approach to promote catalytic performance. Herein, a molybdenum disulfide (MoS₂)-based hybrid with N-doped carbon wrapped CoFe alloy (MoS₂/CoFe@NC) was synthesized through a typical hydrothermal method. The MoS₂/CoFe@NC exhibits excellent electrocatalytic performance with overpotentials of 172 mV for HER and 337 mV for OER at 10 mA cm⁻², and long-term stability of 24-h electrolytic reaction in 1 M KOH solution. The chemical coupling between MoS₂ and CoFe@NC provides improved electronic structures and more accessible active sites. The CoFe@NC substrate accelerates the charge transfer to MoS₂ through a synergistic effect. This work demonstrates that the CoFe@NC is a promising substrate for depositing MoS₂ nanosheets (NSs) to achieve excellent catalytic performance for both HER and OER.     

Flower-like CoS2/MoS2 nanocomposite with enhanced electrocatalytic activity for hydrogen evolution reaction

Molybdenum sulfide (MoS₂) has received tremendous attracts for its promising performance in the aspects of hydrogen evolution reaction (HER). To improve the HER activity of MoS₂, we designed a flower-shaped CoS₂/MoS₂ nanocomposite with enhanced HER electroactivity compared with MoS₂ nanosheets by a simple one-step hydrothermal method. The facile approach brings about distinct transformation of the morphology from nanosheets to nanoflower structures. The introduction of Co element into MoS₂ results in the larger active surface area, more edge-terminated structures, and higher conductivity of the CoS₂/MoS₂ nanocomposite, which are good for improving the HER electroactivity. In brief, the optimized catalyst exhibits the low overpotential of 154 mV at 10 mA cm^?2, small Tafel slope of 61 mV dec^?1, and excellent stability in acidic solution.     

Hollow hexagonal NiSe–Ni3Se2 anchored onto reduced graphene oxide as efficient electrocatalysts for hydrogen evolution in wide-pH range

Integrating transition metal complexes with carbon-based materials, especially graphene, is a useful strategy for synthesizing effective hydrogen evolution catalysts. Herein, we report a design of hollow hexagonal NiSe–Ni₃Se₂ nanosheets grown on reduced graphene oxide (NiSe–Ni₃Se₂/rGO) by a simple hydrothermal method as an effective catalyst for hydrogen evolution reaction (HER) in the full pH range. In 0.5 M H₂SO₄, the NiSe–Ni₃Se₂/rGO possesses 112 mV to achieve 10 mA cm^?2 and a small Tafel slope (61 mV dec^?1). In 1.0 M PBS and 1.0 M KOH, the overpotentials are 261 and 188 mV at 10 mA cm^?2, and Tafel slopes are 103 and 92 mV dec^?1, respectively. Meanwhile, it owns good cycle stability and durability over 20 h in the whole pH range (0-14). In all solutions, the HER performance of NiSe–Ni₃Se₂/rGO is better than that of NiSe–Ni₃Se₂. This is because the rGO substrate accelerates the electron transfer and improves the electrical conductivity, increasing HER activity of catalyst.     

One-step solution-induced impregnation synthesis of strongly coupled platinum–molybdenum/silicon carbide quantum dots heterostructures encapsulated on reduced graphene oxide sheet as electrocatalyst for hydrogen evolution reaction

Strongly coupled platinum-based transition-metal oxide/carbon hybrids and the development of quantum-dot structures of hybrid catalysts are cost-effective and maximize accessible active sites. However, a significant obstacle still exists for the rational proposal and simple synthesis of hybrid quantum-dot material catalysts. Herein, novel Pt_xMo_1-xSiC quantum dots encapsulated in reduced graphene oxide (rGO) (Pt_xMo_1-xSiC QDs @rGO) for catalyzing the hydrogen evolution reaction (HER) were fabricated through a simple solution-induced impregnation method. The optimized Pt₅Mo₉₅SiC QDs @rGO catalyst only require overpotentials of 18 mV and 25 mV to deliver current densities of 10 mA cm⁻² and 250 mA cm⁻² in acidic media, respectively. The synergistic effects of the inner Pt_xMo_1-xSiC QDs networks and outer conductive rGO sheets that promote electron transfer are responsible for the outstanding HER performance. This work presents a novel method for producing an extremely effective HER catalyst for applications on large-scale.     

MoS2/NiFeS2 heterostructure as a highly efficient electrocatalyst for overall water splitting at high current densities

Searching for efficient, stable and low-cost nonprecious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is highly desired in overall water splitting (OWS). Herein, presented is a nickel foam (NF)-supported MoS₂/NiFeS₂ heterostructure, as an efficient electrocatalyst for OER, HER and OWS. The MoS₂/NiFeS₂/NF catalyst achieves a 500 mA cm⁻² current density at a small overpotential of 303 mV for OER, and 228 mV for HER. Assembled as an electrolyzer for OWS, such a MoS₂/NiFeS₂/NF heterostructure catalyst shows a quite low cell voltage (≈1.79 V) at 500 mA cm⁻², which is among the best values of current non-noble metal electrocatalysts. Even at the extremely large current density of 1000 mA cm⁻², the MoS₂/NiFeS₂/NF catalyst presents low overpotentials of 314 and 253 mV for OER and HER, respectively. Furthermore, MoS₂/NiFeS₂/NF shows a ceaseless durability over 25 h with almost no change in the cell voltage. The superior catalytic activity and stability at large current densities (>500 mA cm⁻²) far exceed the benchmark RuO₂ and Pt/C catalysts. This work sheds a new light on the development of highly active and stable nonprecious electrocatalysts for industrial water electrolysis.     

One-step synthesis of oxygen incorporated V–MoS2 supported on partially sulfurized nickel foam as a highly active catalyst for hydrogen evolution

Highly active noble-metal-free catalysts for hydrogen evolution reaction (HER) are essential for the sustainable production of hydrogen. MoS₂ based HER catalysts are potentially competitive to noble metals but facing the challenges of low conductivity, density of active sites and intrinsic activity in basal planes. Herein, oxygen incorporated V–MoS₂ supported on partially sulfurized nickel foam (V–Mo(x)S/NF) are synthesized as binder-free HER catalysts via a one-step in-situ hydrothermal method. By controlling the fed atomic ratios of V/Mo, the optimal V–Mo(0.05)S/NF shows the low HER overpotential of ~31 and ~115 at 10 mA cm⁻² and 100 mA cm⁻², respectively in alkaline electrolyte, which is among the most active noble-metal and noble-metal-free HER catalysts reported. In V–Mo(0.05)S/NF, the introduced V and partially sulfurized nickel foam increases the conductivity. The hedgehog-like morphology ensures the exposure of high-density active sites. More importantly, the incorporated surface oxygen can be readily tuned by the fed atomic ratios of V/Mo, which plays the primary role in promoting the intrinsic HER activity for V–Mo(x)S/NF. This work demonstrates the feasibility of boosting HER through the precise control of incorporated surface oxygen in MoS₂ based catalysts.     

Three-dimensional hierarchical nanoporous (Mn,Ni)-Doped Cu2S architecture towards high-efficiency overall water splitting

Dealloying technique is an important approach to design porous structures and highly active catalysts. In this work, monolithic nanoporous (Mn,Ni)-doped Cu₂S skeletons with controllable composition and tunable porosity are synthesized via dealloying and sulfuration technique. The as-prepared S-np-Mn₇₀Cu₂₉Ni₁ electrode exhibits outstanding catalytic performance toward HER and OER in 1.0 M KOH solution, which drives high current density of 50 mA cm^?2 at the overpotentials of 136 and 317 mV respectively. The excellent catalytic performance is attributed to the unique three-dimensional interconnected bicontinuous nanoporous architecture, which not only exposes high-density catalytic active sites, but also accelerates electron/mass transfer between catalyst surface and electrolyte. Density functional theory (DFT) calculations also reveal that (Mn,Ni)-doped Cu₂S matrix can accelerate water adsorption/dissociation and optimize adsorption-desorption energetics of H intermediates, thus improving the intrinsic HER activity of nanoporous Cu₂S electrocatalysts. Meanwhile, an alkaline water electrolyzer is constructed with the S-np-Mn₇₀Cu₂₉Ni₁ electrode as anode and cathode respectively, depicting remarkable performance in water electrolysis. In the light of advantages such as adjustable composition and tunable porosity in alloying-dealloying process, it offers a new vision for tuning the porosity and catalytic activities of transition metal sulfides and other active catalysts.     

Atomic-scale intercalation of amorphous MoS2 nanoparticles into N-doped carbon as a highly efficient electrocatalyst for hydrogen evolution reaction

The hydrogen evolution reaction (HER) properties of the catalysts are significantly dependent on their microscopic structure. Interfacial engineering at the atomic level is the main approach to design high performance of electrocatalysts. Herein, an interfacial modulation strategy is proposed to fabricate monolayer amorphous MoS₂ nanoparticles with an average of 3.5 nm in diameter stuck in multilayer N-doped carbon (MoS₂/NC), boosting a high HER activity. The amorphous MoS₂ could provide more edge active sites and NC layers endow the fast electron transfer. The XPS, Raman spectra and density functional theory (DFT) calculations reveal that the C–S bond in MoS₂/NC provides the fast electron transfer and decreases H binding energy. Benefiting the unique sandwiched structure, the MoS₂/NC boosts a low overpotential of 152.6 mV at a current density of 10 mA cm⁻², a small Tafel slope of 60.3 mV dec⁻¹, and outstanding long-term stability with 97.3% retention for over 24 h. This strategy provides a new opportunity and development of interfacial engineering for turning intrinsic catalytic activity for water splitting.     

Zinc oxide functionalized molybdenum disulfide heterostructures as efficient electrocatalysts for hydrogen evolution reaction

Technology urges to replace the state-of-the-art catalysts such as platinum with low cost, earth abundant and durable electrocatalysts for efficient hydrogen evolution (HER) reaction which is going to become the major sustainable production of energy in future. Herein, we present the heterostructure based MoS₂.ZnO (MZO) heterostructures for successful electrochemical water splitting process. For HER, the prepared MoS₂.ZnO nanocomposites show the over potential as low as 239 mV at cathodic current density 10 mAcm⁻² with an exchange current density of 3.2 μAcm⁻². A Tafel slope of about 62 mV per decade suggested to have the Volmer-Heyrovsky mechanism for the HER process with MoS₂.ZnO nanocomposite as the catalyst. The small Tafel slope indicates a promising electrocatalyst for HER in practical application. The strong interface formation at the MoS₂.ZnO heterostructure facilitates higher catalytic activity and excellent cycling stability. The heterostructure formation based on semiconductor two dimensional (2D) transition metal dichalcogenides (TMDC) open up new avenues for effective manipulation of HER catalysts.