Enhanced hydrogen evolution reactivity on Mo₂C–Mo₂N composites

Abstract

We have studied the electrolysis of water, by performing a combined experimental and theoretical study of the hydrogen evolution reaction (HER) capability of Mo₂C–Mo₂N composites. Experimentally, we have synthesized nanowires with varying Mo₂C:Mo₂N ratios. We have found that the composites show good HER activity in an acidic medium, that is superior to that of either pristine Mo₂C or Mo₂N. These experimental results are supported by ab initio density functional theory calculations. Interestingly, we find that it is vital to incorporate van der Waals corrections to accurately reproduce the experimentally observed structural transition from an orthorhombic to tetragonal phase as x, the N concentration in Mo₂C_1−xN_x, is increased. By computing Gibbs free energy for H adsorption on Mo₂C_1−xN_x surfaces, our calculations confirm the experimental finding that mixed systems have superior HER activity to pristine systems, with N-rich systems being most active.