Enhancing Alkaline Hydrogen Evolution Electrocatalysis through Hydrogen Spillover in a Ni₃S₂@Cu₂S Heterostructure

Efficient electrocatalysts based on transition metal compounds (TMCs) are essential for advancing water electrolysis technology by facilitating the hydrogen evolution reaction (HER). However, achieving optimal adsorption energy that promotes both hydrogen adsorption and desorption at a single active site is challenging due to significant deviations of the hydrogen adsorption Gibbs free energy (ΔGH) in most transition metals from thermal neutrality. To address this challenge, the hydrogen spillover effect provides a solution by spatially separating hydrogen adsorption and desorption sites. This separation breaks the Sabatier principle and enables catalysts to overcome the constraints imposed by ΔGH, resulting in enhanced catalytic activity. In this study, we examined the triggering conditions for the hydrogen spillover effect and made theoretical predictions indicating that, at the Cu2S/Ni3S2 interface, the internal polarization field (IPF) and the weakened thermodynamic barrier for hydrogen migration can induce this effect. To validate our theoretical predictions, we prepared catalysts with abundant Cu2S@Ni3S2 heterointerfaces for the hydrogen elution reaction (HER). Notably, the catalyst exhibited remarkable performance in a 1.0 M KOH electrolyte, achieving a current density of 10 mA cm–2 with a mere 39 mV overpotential. This study confirms, both theoretically and experimentally, the feasibility of utilizing the hydrogen spillover effect to enhance the catalytic activity of TMCs toward the HER.