Revealing the Synergistic Effect of Cation and Anion Vacancies on Enhanced Fenton-Like Reaction: The Electron Density Modulation of O 2p-Co 3d Bands.

Defect engineering is considered as a flexible and effective mean to improve the performance of Fenton-like reactions. Herein, a simple method is employed to synthesize CoO catalysts with Co-O vacancy pairs (V) for peroxymonosulfate (PMS) activation. Multi-scaled characterization, experimental, and simulation results jointly revealed that the cation vacancies-V contributed to enhanced conductivity and anion vacancies-V provided a new active center for the O generation. CoO-V can optimize the O 2p and Co 3d bands with the strong assistance of synergistic double vacancies to reduce the reaction energy barrier of the "PMS → Co(IV) = O → O" pathway, ultimately triggering the stable transition of mechanism. CoO-V catalysts with radical-nonradical collaborative mechanism achieve the synchronous improvement of activity and stability, and have good environmental robustness to favor water decontamination applications. This result highlights the possibility of utilizing anion and cation vacancy engineering strategies to rational design CoO-based materials widely used in catalytic reactions.