Efficient generation of singlet oxygen for photocatalytic degradation of antibiotics: Synergistic effects of Fe spin state reduction and energy transfer

Abstract

Singlet oxygen (1O2) exhibits excellent degradation performance and stability in removing antibiotics from an aqueous environment. However, its production is limited by free radical competition. This study proposed a photocatalytic method employing ferrihydrite (Fh) as the base, coated with K-doped g-C3N4 and modified by AgCl (Ag/AgCl), leading to the KC3N4/AgCl/Fh composite for efficient 1O2 production. Compared with Fh, the loading of KC3N4 reduced Fe (III) spin, facilitating the rapid conversion of H2O2 to 1O2. The addition of Ag promoted the intersystem crossing process, decreasing the singlet-triplet energy gap from 0.0708 to 0.0458 eV, thereby effectively generating more triplet excitons to convert O2 into 1O2 in a targeted manner. The KC3N4/AgCl/Fh achieved a degradation rate of 98.10 % for enrofloxacin in 30 min, showing high effectiveness and stability. This work suggests a new way to create Fh-based photocatalysts for the efficient production of 1O2.