Reduction tailored NiCoLDH with rich oxygen vacancies boosts peroxymonosulfate activation for efficient tetracycline degradation: Synergy of oxygen vacancies and NiCo dual active sites

Peroxymonosulfate (PMS)-based advanced oxidation is a promising wastewater treatment strategy, yet efficient PMS activation for the rapid removal of refractory organics in waters remains challenging. Herein, a green reductive oxygen vacancy (O V ) engineering strategy mediated by KBH 4 is adopted to tailor NiCoLDH for enhanced PMS activation toward tetracycline (TC) degradation. The structure-activity relationship between relative O V content and the apparent rate constant (k obs ) is systematically elucidated. Results reveal that Ni Co bimetallic sites serve as intrinsic active centers for PMS activation via redox cycling, while O V plays a critical regulatory role by enhancing PMS adsorption, accelerating interfacial electron transfer and generating in situ surface active oxygen (O*) as an electron shuttle to sustain Co 2+ /Ni 2+ regeneration, thereby promoting SO 4 •− and 1 O 2 production. The O V coupled Ni Co dual sites are identified as the actual functional active units for PMS activation. The optimal NiCoLDH 30 achieves a k obs of 0.360 min −1 , 4 times that of pristine NiCoLDH with complete TC removal within 7 min. The catalyst also exhibits good pH tolerance (5–11), anti-interference capacity, and structural stability, maintaining 97% TC removal over 12 h of continuous operation. This work provides a feasible strategy for developing high-performance LDH-based PMS activators.