Boosting electrocatalytic hydrogen evolution over a Mo2C–W2C heterostructure by interface-induced electron modulation

Carbides have a high d-band electronic density of states at the Fermi level and hence characteristics resembling those of platinum. However, due to the strong adsorption of hydrogen intermediates on the surface of the carbides, the kinetics of the hydrogen evolution reaction (HER) is severely limited. Here, we demonstrate a strategy to improve the HER kinetics of carbides by modulating the surface electronic structure. Mo2C–W2C ultrafine nanoparticles on reduced graphene oxide (Mo2C–W2C/RGO) with strong electron interaction are constructed to improve the HER activity. The interfacial interaction between Mo2C and W2C adjusts the electronic structure of the surface, and the favorable hydrogen desorption on this surface is proved by density functional theory calculations. Benefitting from the adjusted electronic structures on the Mo2C–W2C heterointerface, the hydrogen adsorption free energies on both the Mo and W sites of Mo2C–W2C are close to the ideal values (0 eV). As expected, the Mo2C–W2C/RGO exhibits a superior HER activity with ultra-low overpotentials of 81 mV and 87 mV at a current density of −10 mA cm−2 under acidic and alkaline conditions, respectively, as well as remarkable stability. This work reveals the modulating effect of the electronic structure of carbides on the HER activity, which has a profound guiding effect for the directional design of advanced electrocatalysts.