Synergistic effect of photothermal-assisted photocatalysis and S-scheme heterojunction in Mn3O4/BiOI towards efficient pollutants degradation

Abstract

Photocatalytic degradation of antibiotic and organic pollutants in wastewater constituted a pivotal strategy for achieving environmental sustainability. We fabricated a novel S-scheme Mn₃O₄/BiOI heterojunction, further in-depth investigating the photothermal-assisted photocatalytic activity for pollutants degradation. The optimized Mn₃O₄/BiOI-100 composite exhibited superior full-sunlight- induced catalytic activity for tetracycline degradation, demonstrating more 3.29-fold enhancements compared to pristine Mn₃O₄ and BiOI. This performance enhancement arose from the effects of efficient charge separation through the S-scheme mechanism and favorable photothermal catalyst surface. Notably, the composite maintained robust catalytic efficiency in complex aqueous matrices containing various ions. Biological validation through rice seed germination assays revealed complete elimination of phytotoxicity in treated pollutant solutions, realizing the value-added catalytic conversion from nocuous molecules. Radical trapping experiments identified •OH and •O₂^⁻ as primary reactive species, consistent with the proposed S-scheme mechanism subsequently verified by in situ XPS analysis. The photocatalytic degradation and COD removal abilities were also significantly enhanced for other six organic pollutants such as rhodamine B, congo red, methyl orange, methylene blue, p-chlorophenol, and phenol. This study provides a design blueprint for constructing photothermal-assisted S-scheme heterojunction photocatalysts for practical water purification applications.