Integrating oxophilic and protophilic properties in a multivalent Co9S8@CoMoPx electrode to boost alkaline hydrogen evolution†

Abstract

The alkaline hydrogen evolution reaction (HER) is plagued by intricate interfacial reactions involving the dissociation of interfacial H₂O molecules and adsorption/desorption of H_ads/OH_ads species, which impede the practical application of water electrolysis. Herein, a self-supported Co₉S₈@CoMoP_x electrode with a nanosheet cluster morphology was developed using a stepwise electrodeposition method for an efficient electrocatalytic HER. Benefiting from the coexistence of multivalent metal sites, the Co₉S₈@CoMoP_x electrode integrated both oxophilic and protophilic properties to facilitate the cracking of molecular H₂O and subsequent hydrogen generation. As a result, the obtained Co₉S₈@CoMoP_x electrode exhibited superior alkaline HER activities, delivering an overpotential of 226 mV at −500 mA cm⁻² with a low attenuation rate of 11 μV h⁻¹ after 1000 h. An anion-exchange membrane water electrolysis device was then assembled by matching the Co₉S₈@CoMoP_x cathode with an NiFe-based anode to demonstrate its industrial application potential. This work emphasizes the significance of constructing multivalent metal sites to simultaneously achieve oxophilicity and protophilicity, providing a guideline for the rational design of heterostructure electrocatalysts for efficient energy conversion.