Vacancy-mediated dual-step phosphorization-sulfurization of MnMoO4 for efficient acidic hydrogen evolution

Abstract

Developing efficient and acid-stable electrocatalysts from earth-abundant materials remains a central challenge for sustainable hydrogen production. Here, we propose a vacancy-mediated dual-step anion engineering strategy, in which sequential phosphorization and sulfurization cooperatively modulate the electronic structure of MnMoO₄ for acidic hydrogen evolution. Phosphorus incorporation thermodynamically promotes oxygen-vacancy formation, while subsequent sulfur occupation stabilizes defect sites and optimizes the surface coordination environment, yielding a heteroatom-enriched P,S–MnMoO₄ catalyst. As a result, P,S–MnMoO₄ delivers a low overpotential of 198 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ and maintains stable operation over 50 h. Spectroscopic and electrochemical analyses reveal enhanced charge-transfer kinetics and an enlarged electrochemically active surface area induced by cooperative anion incorporation. Density functional theory calculations further demonstrate that P–S co-incorporation strengthens orbital hybridization between active sites and adsorbed H*, achieving a near-optimal hydrogen adsorption free energy and lowering the thermodynamic barrier for the Volmer step. This work establishes a generalizable anion-relay design paradigm for activating metal oxides toward efficient acidic HER.