Vacancy-Mediated Dual-Step Phosphorization-Sulfurization of MnMoO 4 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 dualstep anion engineering strategy, in which sequential phosphorization and sulfurization cooperatively modulate the electronic structure of MnMoO 4 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-MnMoO 4 catalyst. As a result, P,S-MnMoO 4 delivers a low overpotential of 198 mV at 10 mA•cm -2 in 0.5 M H 2 SO 4 and maintains stable operation over 50 h. Spectroscopic and electrochemical analyses reveal enhanced charge-transfer kinetics and enlarged electrochemically active surface area induced by cooperative anion incorporation. Density functional theory calculations further demonstrate that P-S coincorporation 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.