Polyoxomolybdate-derived MoS2/nitrogen-doped reduced graphene oxide hybrids for efficient hydrogen evolution

Integrating MoS₂ with carbon-based materials, especially graphene, is an effective strategy for preparing highly active non-noble-metal electrocatalysts in the hydrogen evolution reaction (HER). This work demonstrates a convenient hydrothermal method to fabricate molybdenum disulfide nanosheets/nitrogen-doped reduced graphene oxide (MoS₂/NGO) hybrids using polyoxomolybdate as the Mo precursor. Introducing more defects and expanding interlayer spacing of MoS₂ can be achieved through decreasing the pH value of the reactive system due to the existed high-nuclear polyoxometalate clusters. MoS₂/NGO hybrids prepared at low pH exhibit superior HER activity to those obtained at high pH. MoS₂/NGO-pH1.5 exhibits an ultralow overpotential of 81 mV at 10 mA cm⁻², a low Tafel slope of 60 mV·dec⁻¹ and good stability in alkaline electrolyte. Such excellent electrocatalytic activity is contributed by the abundant HER catalytic active sites, the increased electrochemically-accessible area and the synergetic effects between the active MoS₂ catalyst and NGO support.