The intrinsic hydrogen evolution performance of 2D molybdenum carbide

Molybdenum carbide (Mo2C), a member of transition metal carbides (TMCs), has shown promise in water splitting. Although excellent hydrogen evolution reaction (HER) performance of Mo2C has been achieved both in acid and basic media, the intrinsic hydrogen evolution ability of two-dimensional (2D) Mo2C is still not clear due to the difficulty of calculating the actual active surface area involved in the HER. In this work, the HER activity of Mo2C nanosheets is measured on single 2D Mo2C, which is synthesized through low-temperature carbonization of 2D molybdenum dioxide (MoO2) nanosheets on a SiO2/Si substrate. The edge sites of Mo2C exhibit high catalytic activity with a small Tafel slope of 40.2 mV dec(-1) and an overpotential of 152 mV for 10 mA cm(-2) in alkaline media. Theoretical analyses reveal that the energy barriers for cleaving the OH-H bond in H2O on the edge of Mo2C are much smaller than those on the basal plane of Mo2C and the Mo site of the edge of Mo2C displays the optimal Delta G(H) for the H absorption.