Multi-Interface MnIn2S4/ZnIn2S4/CdIn2S4 heterojunction with stepwise charge transfer enables efficient H2O2 photoproduction and photo-self-Fenton TC degradation

Tetracycline (TC), as a persistent and widely detected antibiotic pollutant, poses severe ecotoxicological risks and necessitates rapid and efficient degradation strategies. Here, we demonstrate a photocatalytic self-Fenton process in which H 2 O 2 produced via visible-light-driven oxygen reduction is directly activated by Fe species for the rapid degradation of TC. To enable efficient H 2 O 2 production, a ternary ZnIn 2 S 4 / CdIn 2 S 4 /MnIn 2 S 4 (denoted as ZC 0.3 M 0.05 ) heterojunction photocatalyst was rationally constructed via a one-pot hydrothermal method. Structural analyses reveal that the three sulfides form a tightly coupled, multi-interfacial nanoscale architecture that induces pronounced interfacial strain and charge polarisation. Consequently, ZC 0.3 M 0.05 delivers a high H 2 O 2 production rate of 4907.7 μmol g⁻ 1 h⁻ 1 , outperforming pristine ZnIn 2 S 4 , CdIn 2 S 4 and MnIn 2 S 4 by factors of 15.2, 10.7 and 13.6, respectively. Upon Fe addition, the in situ generated H 2 O 2 enabled rapid self-Fenton degradation of TC, achieving 91.9 % removal within 5 min, while maintaining high activity under simulated environmental conditions. Combined spectroscopic, electrochemical and theoretical analyses reveal that work-function-difference-driven and stepwise electron-transfer pathways (MnIn 2 S 4  → ZnIn 2 S 4  → CdIn 2 S 4 ) across multiple heterointerfaces facilitate efficient charge separation and O 2 -to-*O 2 ⁻ electron injection. This work establishes a materials framework for on-demand H 2 O 2 production and direct self-Fenton pollutant remediation, and offers general design principles for high-performance ternary metal sulfide heterojunctions.