Electrocatalyst Design: Directional Proton Drift via Free Energy Gradient Leading to Enhanced Hydrogen Evolution Reaction.

Abstract

Large-scale green hydrogen production via the electrocatalytic hydrogen evolution reaction (HER) in alkaline media is often limited by the sluggish Volmer step. Herein, we present a HER catalyst, engineered by depositing Fe₁Co₁ alloy onto a Ni₃S₂ substrate. This architecture promotes directional proton drift from the proton-accepting alloy to Ni₃S₂, driven by a Gibbs free energy gradient, thereby enhancing hydrogen desorption and accelerating HER kinetics. The minimal work function difference (ΔΦ ≈ 0.05 eV) between the alloy and substrate ensures optimal interfacial charge distribution, while the heterogeneous interface generates distinct active sites for hydrogen adsorption and efficient migration. As a result, the catalyst achieves 10 mA cm^-2 at an overpotential of only 66 mV and maintains an outstanding durability, operating for 200 h at 100 mA cm^-2. Ab initio calculations confirm that the Fe₁Co₁-Ni₃S₂ interface lowers both thermodynamic and kinetic barriers for water dissociation and fine-tunes hydrogen intermediate binding, leading to rapid desorption.