Nesting CoMo Binary Alloy Nanoparticles onto Molybdenum Oxide Nanosheet Arrays for Superior Hydrogen Evolution Reaction.

Transition-metal alloys have attracted a great deal of attention as an alternative to Pt-based catalysts for hydrogen evolution reaction (HER) in alkaline. Herein, a facile and convenient strategy to fabricate CoMo binary alloy nanoparticles nesting onto molybdenum oxide nanosheet arrays on nickel foam is developed. By modulating the annealing time and temperature, the CoMo alloy catalyst displays a superior HER performance. Owing to substantial active sites of nanoparticles on nanosheets as well as the intrinsic HER activity of CoMo alloy and no use of binders, the obtained catalyst requires an extremely low overpotential of only 68 mV at 10 mA cm in alkaline, with a corresponding Tafel slope of 61 mV dec. At the same time, the catalyst demonstrates excellent stability during the long-term measurements. The density functional theory calculation provides a deeper insight into the HER mechanism, unveiling that the active sites on the CoMo-based catalyst are Mo atoms. This strategy of combining catalytic active species with hierarchical nanoscale materials can be extended to other applications and provides a candidate of nonnoble metal catalysts for practical electrochemical water splitting.