Air-stable phosphorus-doped molybdenum nitride for enhanced elctrocatalytic hydrogen evolution

Molybdenum-based electrocatalysts for hydrogen evolution have been investigated extensively in recent years. However, unlike other non-oxides, molybdenum nitride generally shows a weak preference for hydrogen evolution and low performance owing to surface oxidation and the strong Mo–H bond. Here, we prepare an air-stable molybdenum nitride through a multi-step solid-state reaction. We find that a uniformly dispersed mixture of the precursors is optimal for preparation of the electrocatalyst. To further enhance hydrogen evolution performance towards practical device applications, phosphorus doping is carried out, using a few layered black phosphorus source. The phosphorus-doped molybdenum nitride (P–Mo–N) sample catalyzes hydrogen evolution with potentials of 105, 145, and 157 mV at the current densities of 10, 50, and 100 mA/cm², respectively, in 0.5 M H₂SO₄ solution with a small Tafel slope of 43 mV/dec. Thus it outperforms many of the state-of-art molybdenum-based hydrogen evolution catalysts reported to date.