Novel synthesis of molybdenum phosphide employing a single source precursor and its use as a hydrogen evolution catalyst with broad pH activity

Abstract

Molybdenum phosphide is a promising noble-metal-free catalyst for the H₂ evolution reaction. The synthesis of molybdenum phosphide was usually delicate, requiring a mixture of Mo and P precursors and hard reaction conditions. Herein, we report on a novel strategy for synthesizing molybdenum phosphide by employing a molybdenum complex, namely [Mo^III(dppe)I₃DMF] wherein dppe is 1,2-bis(diphenylphosphino) ethane, as the single precursor source. The synthesis, structural characterization and thermal behaviour of [Mo^III(dppe)I₃DMF], being a novel Mo^III complex, was described. The thermal decomposition of [Mo^III(dppe)I₃DMF] generating hexagonal crystalline molybdenum phosphide was investigated in details showing the impacts of decomposition temperature to the product's morphology, chemical composition and crystallinity. The best molybdenum phosphide was obtained at 800 °C which showed attractive catalytic activities for the H₂ evolution in acidic, neutral and alkaline electrolytes. It displayed an onset potential at −0.13 V vs. RHE and required −0.3 V vs. RHE to sustain the benchmarking catalytic current density of 10 mA/cm². It was found to be stable during the H₂ evolution catalysis.