Engineering Mo–O Covalency via P-Doping for Enhanced Hydrogen Evolution

The metal–oxygen covalent bond in transition metal oxides significantly influences oxygen electrocatalysis, yet its role in the hydrogen evolution reaction (HER) remains poorly understood. In this study, we develop a P-doped MoO3 (P-MoO3) electrocatalyst with enriched oxygen vacancies and modulated electronic structure, revealing the influence of Mo–O covalency on HER activity. Experimental and theoretical analyses indicate that phosphorus incorporation into the MoO3 lattice expands the band gap between Mo 4d and O 2p orbitals, weakens the Mo–O covalency, and shifts the d-orbital center, collectively optimizing hydrogen adsorption energy and enhancing HER activity. Leveraging these features, the P-MoO3 electrocatalyst achieves high activity, demonstrating a low overpotential of 109 mV at 10 mA cm–2 in alkaline electrolyte. This work provides fundamental insights into the role of Mo–O covalency in HER, offering a novel perspective on water-splitting electrocatalyst design.