Design Superior Alkaline Hydrogen Evolution Electrocatalyst by Engineering Dual Active Sites for Water Dissociation and Hydrogen Desorption.

Abstract

In alkaline media, the water-dissociation-related Volmer process always suppresses the hydrogen formation/desorption process, which makes it challenging to develop non-noble-metal alkaline electrocatalysts with excellent catalytic activity. Here, we proposed a two-pronged strategy to simultaneously promote the kinetic process of both water dissociation and hydrogen desorption with the Co-doped WO2/amorphous CoxW hybrid electrocatalyst. Impressively, the optimized hybrid exhibits an outstanding hydrogen evolution reaction (HER) activity with the quite small Tafel slope of 19.77 mV dec-1 and ultralow overpotential of just 25 mV to reach a current density of 10 mA cm-2 in alkaline media. Both experiments and density functional theory calculations reveal that the top-level HER performance can be attributed to the cooperation of two different active components, in which the water molecule can easily be activated on the amorphous CoxW with low energy barrier (ΔGw = 0.46 eV), while hydrogen atoms can rapidly desorb from the Co-doped WO2 with an optimal Gibbs free energy of hydrogen adsorption (ΔGH* = -0.06 eV). Also, the density functional theory calculation further confirms that the H* tends to combine with another H* via Tafel step rather than Heyrovsky step. The findings provide unique insights for the development of the state-of-the-art non-noble-metal HER electrocatalyst with a Pt-like kinetic behavior in alkaline media.