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

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 Co_xW 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 Co_xW with low energy barrier (ΔG_w = 0.46 eV), while hydrogen atoms can rapidly desorb from the Co-doped WO₂ with an optimal Gibbs free energy of hydrogen adsorption (ΔG_H* = -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.