Silver Oxide-Driven Far-UVC Fenton-like Wastewater Treatment: Hole-Induced High-Valent Silver Formation

Abstract

Efficient photo-Fenton-like catalysis remains limited by inefficient coupling between charge-carrier utilization and peroxide activation. Here, we develop a synergistic UV222/H2O2/Ag2O process integrating far-UVC photolysis, peroxide activation, and Ag2O catalysis within a unified Fenton-like framework. In real secondary effluent, the ternary process delivers a total organic carbon removal rate constant of 0.117 min–1, which is 1.8 times that of the UV222/H2O2 system (0.065 min–1) and far superior than UV254-based counterparts; while enabling 7-log Escherichia coli inactivation within 6 min. The process also exhibits broad pH tolerance, resistance to anionic interference, and high operational stability. Mechanistically, H2O2 adsorbs onto Ag2O in a bidentate configuration, forming silver-coordinated hydroxyl groups (Ag2O*-*OH) that undergo hole-triggered deprotonation to yield transient interfacial high-valent AgII-oxo species. Density functional theory calculations show that hole capture lowers the deprotonation energy barrier from 2.43 to 0.67 eV, facilitating AgII-oxo formation. These nonradical oxidants operate via single-electron transfer, complementing radical pathways. The treated effluent shows improved clarity and stability, as confirmed by molecular-level analysis. Life cycle assessment and stable continuous operation with limited silver release using Ag2O-sodium alginate gel spheres demonstrate practical potential. This work highlights the critical role of photoexcited holes in advancing photo-Fenton-like catalysis for sustainable environmental remediation.