Co-induced Fe2+ generation and oxygen vacancy construction to synergistically boost the photoelectro-Fenton performance of α-Fe2O3 for tetracycline hydrochloride degradation

Tetracycline hydrochloride (TCH) has emerged as a pressing environmental issue due to their extensive use and recalcitrant nature. The integration of Fenton reaction with photoelectrocatalysis, forming a photoelectro-Fenton system, is emerging as a promising strategy for advanced water treatment. This study aims to address the critical challenges of severe charge recombination and sluggish surface reaction kinetics in α-Fe 2 O 3 during photoelectrocatalytic pollutant degradation. Through Co-doped modification, Fe 2−x Co x O 3 photoanodes were successfully fabricated. The results demonstrate that partial substitution of Fe 3+ by Co 2+ not only effectively enhances charge carrier concentration but also induces the formation of substantial oxygen vacancies. This synergistic effect consequently leads to significantly improved electrical conductivity and expanded visible-light absorption range. Firstly, Co 2+ functions as an electron donor, continuously reducing Fe 3+ to Fe 2+ and thereby sustaining the cycling of the Fe 3+ /Fe 2+ . Concurrently, this process facilitates the efficient and continuous conversion of oxygen to H 2 O 2 via a two-electron reduction pathway. Secondly, the coexisting Co 2+ /Co 3+ and Fe 2+ /Fe 3+ bimetallic cycles on the material surface enabling sustained activation of H 2 O 2 to trigger the Fenton reaction, which generates substantial amounts of highly reactive hydroxyl radicals (·OH) and other active substances, achieving rapid decomposition and mineralization of TCH molecules.