Novel CoP Hollow Prisms as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction in Acid media and Overall Water-splitting in Basic media

•Hollow CoP prisms have been synthesized using Co3(CH3COO)5(OH) cubes as precursors.•Hollow CoP prisms have excellent activity and stability for HER in acid media.•Hollow CoP is a bifunctional electrocatalyst for HER and OER in alkaline media.•The amorphous oxygen-containing species on CoP may be real active sites for OER.

Cobalt phosphide (CoP) with hollow prisms nanostructure has been successfully synthesized via a facile two-step micro-assisted method. Firstly, uniform Co3(CH3COO)5(OH) cubes are prepared by microwave method. Then as-prepared Co3(CH3COO)5(OH) cubes as precursors have been conducted by phosphorization at low temperature. Novel CoP hollow prisms with 1 μm length, 500 nm width and 500 nm height have been synthesized. The obtained CoP hollow prisms can be used as both an efficient electrocatalyst for HER in acid media (0.5 M H2SO4 solution) and a remarkable bifunctional electrocatalyst for overall water-splitting in alkaline media (1.0 M KOH solution) which might be attributed to their high surface area, porosity and good distribution. The OER mechanisms of CoP in alkaline solution have been investigated through XPS and SEM Mapping, which demonstrate that the amorphous oxygen-containing nanostructure on the surface of CoP may be the real catalytic active species. In addition, phosphidation of uniform cobalt salt hydrates precursor with specific structure at low temperature is a newfangled and effective strategy to synthesis bifunctional electrocatalyst CoP.

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