Electrochemically synthesized N-doped molybdenum carbide nanoparticles for efficient catalysis of hydrogen evolution reaction

An efficient catalyst for hydrogen evolution reaction (HER), nanostructured nitrogen-doped molybdenum carbide (β-Mo 2 C), is reported in this work. The catalyst is prepared via a novel one-step solid-state electrolytic reduction of a mixture of MoS 2 and polypyrrole nanofiber in molten CaCl 2 at 850 °C. As comparison, a series of Mo 2 C materials are prepared by the method using different carbon precursors. TEM tests show that the as-prepared N-doped Mo 2 C is composed of near-spherical nanoparticles with the particle sizes of about 40–60 nm. Nitrogen-doping of Mo 2 C is shown to facilitate the exposure of active centers on the surface of the sample, concurrently modify the electronic property of Mo 2 C to promote electron transfer for HER. As a result, the optimized N-doped Mo 2 C (Mo 2 C- PPyF -1/1) displays a low onset potential of 78.1 mV for HER and a Tafel slope of 59.6 mV dec −1 in 0.5 M H 2 SO 4 , meanwhile exhibits high activity and stability in a broad pH range (0–14). Furthermore, the synthesis method is extended to fabricate other N-doped transition metal carbides (NbC, TaC and TiC). All of the N-doped materials exhibit significantly enhanced activity compared to the undoped ones.