A Universal pH range and Highly-efficient Mo2C-based Electrocatalyst for the Hydrogen Evolution Reaction

Electrochemical water splitting is a promising way to generate ‘green’ hydrogen. The efficiency of this process relies on the effectiveness of the electrocatalysts used. The electro-kinetics of the hydrogen evolution reaction (HER) is highly pH dependent and conventional catalysts typically employ expensive and rare platinum-based materials. The development of low-cost, multi-component electrocatalysts, where each of the components has a synergistic effect, can be an effective approach to improve kinetics. Herein, a series of transition metal (Fe, Mn, Co, Ni)-modified molybdenum carbides in a nitrogen-doped carbon matrix (TM-Mo2C@NCF) are synthesised to maximise exposed active sites. Among which, Fe-Mo2C@NCF deliver the best-in-class HER performance over a wide range of electrolytes. Tafel slopes of 76, 109 and 110 mV dec-1 and overpotentials of 65, 130 and 129 mV at 10 mA cm-2 were obtained in 1.0 M KOH, 1.0 M phosphate buffer solution (PBS) and 0.5 M H2SO4, respectively. The computational study further indicates that the synergistic electronic modulation co-activated by Fe and N dopants in Fe-Mo2C@NCF can reduce the Gibbs free energy of H adsorption (∆GH*) and render the Mo-Mo bridge site the most energetically favorable adsorption site for H* intermediate, which contributes to an increased HER performance.