Highly dispersed Ni2−Mo P nanoparticles on oxygen-defect-rich NiMoO4− nanosheets as an active electrocatalyst for alkaline hydrogen evolution reaction

Development of high-performance electrocatalysts requires a comprehensive consideration of intrinsic activity, number of active sites and electrical conductivity. Herein, we report the facile synthesis of a highly active electrocatalyst towards alkaline hydrogen evolution reaction (HER), which involves a joint application of composition modulation, nanostructuring and defect engineering strategies to address the three key issues. A 3D hierarchically nanostructured Ni2−xMoxP/NiMoO4−y catalyst is synthesized using hydrothermal in combination with phosphorization methods. Phosphorization treatment of the ammonium nickel molybdate precursor results in the concurrent formation of highly dispersed Mo-doped Ni2P nanoparticles and oxygen-defect-rich NiMoO4−y substrate, which work in concert to provide synergistic active sites for alkaline HER. The presence of abundant oxygen-vacancies in NiMoO4 lattice leads to significant improvement of electrical conductivity. Furthermore, the nanoporous hierarchical structure of the catalyst promises abundance of accessible active sites and an improved reactant/product mass transfer kinetics. As a consequence of the favorable combination of these attributes, the non-precious Ni2−xMoxP/NiMoO4−y catalyst exhibits an intriguing catalytic performance towards the HER in alkaline solution, with an overpotential of ~36 mV at a current density of 10 mA cm−2 and a Tafel slope of 53 mV dec−1, which are among the best reported values of noble-metal-free electrocatalysts for alkaline HER.