Defect engineering and electron transfer mediating dual activation for antibiotic degradation and heavy metal...

Heterojunction photocatalysts are widely applied in advanced water treatment, yet their performance for simultaneous oxidative removal of organic pollutants and reductive detoxification of hexavalent chromium (Cr(VI)) remains constrained by insufficient interfacial activity and stability. Herein, we address this challenge by transforming industrial aluminum ash waste into a stable, nitrogen-doped carbon/Al₂O₃ (NC/Al₂O₃) composite via in situ derivation, and precisely constructing an Fe-MoS₂ heterojunction catalyst (Fe-MoS₂@NC/Al₂O₃) thereon. The resulting architecture leverages synergistic interfacial defects, a conductive 1 T/2H mixed-phase MoS₂, and an accelerated Fe^2 +/Fe³⁺ redox cycle to establish dual active sites with distinct electron-transfer channels. Combined EPR spectroscopy, chemical probe assays, and electrochemical analyses reveal a dual-channel reaction mechanism in the respective systems: (i) peroxymonosulfate (PMS) activation generates hydroxyl radicals (HO^.), sulfate radicals (SO₄^.-) alongside direct electron transfer to oxidize and mineralize tetracycline hydrochloride (TCH); (ii) formic acid (FA) mediates hydrogen radical (H^.) formation while heterojunction-facilitated electron transfer reduces toxic Cr(VI) to Cr(III). Density functional theory (DFT) calculations further elucidate the synergistic enhancement of catalytic activity by interfacial sulfur vacancies and Fe/Mo bimetallic sites. The catalyst achieved 100% removal of TCH and Cr(VI) in batch tests and exhibited exceptional stability, retaining 96.7% and 97.5% removal efficiency over 30 continuous-flow cycles. Product analysis confirmed significantly reduced environmental toxicity after TCH degradation. Collectively, this work pioneers a waste-to-catalyst approach and delivers a material that effectively decouples redox pathways, providing a scalable blueprint for advanced water treatment.