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 (beta-Mo2C), is reported in this work. The catalyst is prepared via a novel one-step solid-state electrolytic reduction of a mixture of MoS2 and polypyrrole nanofiber in molten CaCl2 at 850 degrees C. As comparison, a series of Mo2C materials are prepared by the method using different carbon precursors. TEM tests show that the as-prepared N-doped Mo2C is composed of near-spherical nanoparticles with the particle sizes of about 40-60 nm. Nitrogen-doping of Mo2C is shown to facilitate the exposure of active centers on the surface of the sample, concurrently modify the electronic property of Mo2C to promote electron transfer for HER. As a result, the optimized N-doped Mo2C (Mo2C-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 MH2SO4, 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. (c) 2017 Elsevier Ltd. All rights reserved.