Mo2C/VC heterojunction embedded in graphitic carbon network: An advanced electrocatalyst for hydrogen evolution

Pt-free metal carbide electrocatalysts with high activity are highly desirable for the hydrogen evolution reaction (HER) in economical and large-scale water splitting. However, pure-phase carbides suffer from mismatching hydrogen adsorption/desorption kinetics. Herein, Mo2C and VC nanoparticles are embedded in a three-dimensional (3D) graphitic carbon network (Mo2C/VC@C) via phase separation of V2MoO8 with NaHCO3 as the carbon source in a magnesiothermic reduction process. The Mo2C/VC heterojunction with abundant interfacial area and exposed active sites not only lead to moderate hydrogen adsorption energy and enhanced deasorption kinetics, but also facilitate efficient electron transfer. Moreover, the 3D carbon network provides high conductivity and structural support. The Mo2C/VC@C catalyst exhibits a low overpotential of 122 mV at a current density of 10 mV cm(-2) with a small Tafel slope of 43.8 mV dec(-1) in addition to outstanding stability for over 10,000 cycles. Density-functional theory calculations reveal that the heterointerface of Mo2C/VC adjusts the electronic structures of Mo2C and VC and lowers the binding energy with hydrogen to enhance the HER performance. The concept, synthesis method, and materials properties described here provide insights into future development of high-efficiency HER catalysts for commercial water splitting.