Co-P-O bridges enabling spin-related interfacial charge regulation for synchronizing redox kinetics in dual-pollutant...

Removing antibiotics and toxic heavy metals from complex wastewater is often limited by kinetic mismatch between oxidation and reduction processes during coupled treatment. Herein, a CoP/TiO₂ photoelectrocatalytic heterojunction with an engineered Co-P-O interfacial configuration was developed to regulate interfacial charge transfer and synchronize redox reactions. The interfacial P species are proposed to act as electron-mediating centers, facilitating directional electron transport and potentially contributing to spin-related interfacial charge-transfer characteristics. Control experiments using Co(OH)₂/TiO₂ and CoO/TiO₂ indicate that the enhanced performance originates primarily from P incorporation rather than thermal transformation or Co phase evolution. Experimental observations combined with theoretical calculations support a plausible Co-P-O interfacial linkage that promotes charge redistribution and reduces interfacial resistance, although direct atomic-scale verification remains challenging. Mechanistic investigations suggest that the system operates via a multi-reactive-species pathway involving radicals, photogenerated holes, and possible non-radical processes, rather than a single dominant oxidant. This cooperative mechanism may facilitate electron utilization for both persulfate activation and Cr(VI) reduction, likely involving a dynamic Co²⁺/Co³⁺ redox cycle. The optimized electrode achieved 94.6% removal of metronidazole and 99.9% reduction of Cr(VI) within 60 min. In addition, the system exhibits excellent stability over 30 cycles with negligible structural degradation and low metal leaching. Significant mineralization and toxicity reduction are confirmed by total organic carbon analysis and luminescent bacteria assays. This work highlights the importance of interfacial electronic regulation in overcoming redox kinetic mismatch and provides a feasible strategy for efficient and environmentally relevant dual-pollutant treatment.