In-situ synthesis of coupled molybdenum carbide and molybdenum nitride as electrocatalyst for hydrogen evolution reaction

Searching for high-efficiency and earth-abundant electrocatalysts towards hydrogen evolution reaction (HER) is one of the most promising pathways to ameliorate environmental contamination. In this work, we report a facile protocol to achieve the synthesis of the coupled molybdenum carbide and molybdenum nitride (Mo2C/Mo2N), in which ammonium heptamolybdate (AHM) serves as molybdenum source and hexamethylenetetramine (HMT) is chosen as a N-containing carbon source. By virtue of adjusting the ratios of precursors and carbonization temperatures, a variety of products with different structural features and HER performance can be obtained. Compared to single component of carbide or nitride, the Mo2C/Mo2N hybrid prepared with AHM/HMT ratio of 1:2 at 700 °C shows superior catalytic activity, with an overpotential of 205 mV required to drive 10 mA cm−2 of current density and a Tafel slope of 71.8 mV dec−1. The boosted HER performance is attributed to the synergistic effect between Mo2C and Mo2N, and the electronic modulation of active sites due to N-doping.