A nanocrystalline oxygen-deficient bismuth oxide as an efficient adsorbent for effective visible-light-driven photocatalytic performance toward organic pollutant degradation

Rapidly degradation of di-(2-ethylhexyl) phthalate by Z-scheme Bi2O3/TiO2@reduced graphene oxide driven by simulated solar radiation

Di(2-ethylhexyl) phthalate (DEHP) is a priority environmental pollutant with carcinogenic, teratogenic, and mutagenic toxicity. Because it is widely used and ubiquitous in water, it is urgent to use a non-toxic, fast, and non-temperature dependent photocatalyst for degradation. Herein, a Z-scheme heterojunction composite catalyst consisting of Bi₂O₃ and TiO₂ with reduced graphene oxide (rGO) as a two-dimensional template was designed and characterized. Under simulated solar radiation, the catalyst doped with 4% rGO presented the best photocatalytic DEHP (10 mg L^-1) degradation at pH = 6, reaching 89% conversion in 90 min, and the degradation rate was 2.05 times higher than unmodified materials. The successful preparation of the Z-scheme junction enhanced the utilization of visible light region, thereby improving the DEHP's photocatalytic degradation performance. Subsequently, density functional theory (DFT) combined with GC-MS metabolite detection to propose a complete DEHP photocatalytic degradation mechanism. ·O₂^- and ·OH were detected as the primary reactive oxygen radicals involved in DEHP degradation, which easily attacked the O11 site with a high Fukui index (f⁰) through de-esterification, β-oxidation, and hydroxylation. While satisfying the rapid degradation, the highly repeatable catalyst cleaved the aromatic ring so that DEHP achieved mineralization during the degradation process. Therefore, its ability to completely degrade was very promising for environmental remediation, especially in water treatment. Besides, there were only a few studies on the degradation mechanism and reaction pathway of DEHP under visible light, which provided a theoretical basis for the aromatic compounds' photocatalysis research.