Investigation on the photocatalytic degradation properties of BiOX on carbendazim and its mechanism

Abstract Bismuth Oxyhalide (BiOX, X=Cl, Br, I) has been widely used in water purification, environmental remediation and other fields due to its special layered structure and good photocatalytic performance. In this work, BiOCl, BiOBr and BiOI photocatalysts were successfully synthesized by a simple solvothermal method and first applied to the mineralization and degradation of carbendazim (CBZ). The degradation performance of BiOX to CBZ was studied under different light sources and different pH conditions. And the influence mechanism of the degradation performance of the three catalysts were revealed by analyzing the structure, morphology, specific surface area, optical performance, energy band structure, and electronic density of state of the materials. The results showed that, under the irradiation of metal halide lamp, the photocatalytic activity of BiOBr was the best when the pH was at 7. The degradation efficiency reached 99 % after 3 h and more than 90 % CBZ molecules could be mineralized. The BiOBr catalyst had good stability in four cycles. Furthermore, it was found that the main active species were h + and ⋅O 2 − in the photodegradation process by free radical trapping experiment. Based on the density functional theory (DFT) calculation, it was demonstrated that different halogen atoms had different density of state contribution intensity in atomic orbitals, different band gap width and different light response capabilities by the analysis of its energy band structure and partial wave density of state (PDOS), resulting in different photocatalytic performance under different energy light irradiation.