The synergy of step-scheme heterojunction and sulfur vacancies in AgInS2/AgIn5S8 for highly efficient photocatalytic degradation of oxytetracycline

Abstract

Constructing heterojunction and engineering intrinsic defect in the electronic structures of semiconductor photocatalysts have been recognized as useful strategies to meliorate their photocatalytic performance. Herein, AgInS₂/AgIn₅S₈ step-scheme(S-scheme) heterojunction photocatalysts with abundant sulfur vacancies were obtained via one-step hydrothermal method by using L-cysteine as complexing agent. The optimal AgInS2/AgIn5S8 exhibited a high removal efficiency of 90.5% in the photocatalytic degradation of oxytetracycline under visible light irradiation and could achieve a TOC removal rate of 61.0%. Moreover, the AgInS₂/AgIn₅S₈ displayed a good long-term stability and reusability during consecutive application. The superior photocatalytic activity could be attributed to the rapid charge transfer under the driving force of internal electric field formed on the S-scheme heterojunction interface. The analysis results of degradation intermediates revealed that oxytetracycline was decomposed into small nontoxic molecules via deamination, dehydroxylation, decarbonylation and demethylation reactions by the attack of main active h⁺ and •O₂^– radicals. This study paves a new way to rationally design the novel AgInS₂/AgIn₅S₈ step-scheme photocatalysts for antibiotic pollution remediation in water environment.