Relaying alkaline hydrogen evolution over locally amorphous Ni/Co-based phosphides constructed by diffusion-limited phase-transition

Abstract

Ni/Co-based phosphides are a family of promising electrocatalysts for hydrogen evolution reaction (HER), but the sluggish water dissociation kinetics impedes their applications in alkaline condition. Herein, locally amorphous NiCoP (LA-NiCoP) with enhanced orbital coupling to facilitate water dissociation is constructed by a low-temperature molten salt enabled diffusion-limited phase-transition strategy. Time-dependent experiment systematically clarifies the crystallinity regulation mechanism of NiCoP associated with its nonclassical crystallization process of amorphous-to-crystalline transition. As the alkaline HER electrocatalyst, LA-NiCoP exhibits a close to Pt/C activity (ƞ10 =45 mV). Both experimental and theoretical results show that the Co atoms in the amorphous phase display higher proportion of unoccupied 3d orbitals than the crystalline counterpart, which interacts with the O 2p of H2O for activating the cleavage of HO–H bond. This work not only provides a facile approach to prepare locally amorphous phosphides, but also offers a new protocol to accelerate the water dissociation kinetics.