Dual-phase MoC-Mo2C nanosheets prepared by molten salt electrochemical conversion of CO2 as excellent electrocatalysts for the hydrogen evolution reaction

Dual-phase structures usually have better electrocatalytic activity in the hydrogen evolution reaction (HER) due to synergistic effects. Herein, a novel strategy is proposed to prepare dual-phase MoC-Mo2C nanosheets by electro-reduction of CO2 on the Mo cathode in CaCl2-CaO molten salts through an in situ reaction between molybdenum and carbon. The composition of the molybdenum carbide samples can be adjusted by the cell voltage and temperature. As the Mo2C contents go up, the HER activity of molybdenum carbide increases initially and then decreases slightly. The dual-phase MoC-Mo2C nanosheets prepared at 850 °C and 2.5 V show the best activity due to the hydrogen adsorption-desorption balance. The results reveal an innovative and sustainable strategy to prepare highly efficient HER electrocatalysts and also a green route to recycle and utilize CO2.