Experimental and theoretical confirmation of CeFeCu trimetal oxide/Bi2O3 S-scheme heterojunction for boosted photocatalytic degradation of sulfamethoxazole and toxicity evaluation

Photocatalytic degradation of pharmaceutical pollutants in water or wastewater is becoming a hot topic for environmental clean-up. Herein, a novel CeFeCu trimetal oxide (CFC TMO)/Bi₂O₃ (CFCB) photocatalysts were prepared through precursor mixing, ultrasonication, and calcination methods and used for photocatalytic degradation of sulfamethoxazole (SMZ). The pseudo-first order kinetic rate of CFCB-2 catalyst on degradation of SMZ reached 0.0577 min⁻¹ which is 4.93 and 10.02 times higher than of α-Bi₂O₃ and CFC TMO under visible light illumination. This was proved by the strong interaction between the pristine materials as confirmed by XPS and density functional theory (DFT) calculations. DFT calculations indicated that having more orbital distribution could make it easier to capture more electrons and produce more radicals through electron transfer. Meanwhile SMZ by-products showed no sign of cytotoxicity towards human embryonic kidney cell line (HEK 293) and human intestinal epithelial cell line (CACO-2). The findings of the scavenger experiments and ESR measurements proved that •OH and •O₂⁻ radicals played superior role in decomposition of SMZ. Furthermore, the S-scheme charge carrier transfer and degradation pathway of SMZ are proposed and analysed. This study paves ways into promising strategy for the construction of α-Bi₂O₃ based novel S-scheme heterojunction for environmental decontamination and can be extended to other applications such as Fenton-like reactions and persulfate activation.