Vanadium-Incorporated CoP₂ with Lattice Expansion for Highly Efficient Acidic Overall Water Splitting

A proton exchange membrane water electrolyzer (PEMWE) in acidic medium is a hopeful scenario for hydrogen production using renewable energy, but the grand challenge lies in substituting noble-metal catalysts. Herein, a robust electrocatalyst of V-CoP₂ porous nanowires arranged on a carbon cloth is successfully fabricated by incorporating vanadium into the CoP₂ lattice. Structural characterizations and theoretical analysis indicate that lattice expansion of CoP₂ caused by V incorporation results in the upshift of the d-band center, which is conducive to hydrogen adsorption for boosting the hydrogen evolution reaction (HER). Besides, V promotes surface reconstruction to generate a thicker Co₃ O₄ layer with an oxygen vacancy that enhances acid-corrosion resistance and optimizes the adsorption of water and oxygen-containing species, thus improving activity and stability toward the oxygen evolution reaction (OER). Accordingly, it presents a superior acidic overall water splitting activity (1.47 V@10 mA cm^-2 ) to Pt-C/CC||RuO₂ /CC (1.59 V@10 mA cm^-2 ), and remarkable stability. This work proposes a new route to design efficient non-noble metal electrocatalysts for PEMWE.