Facile synthesis of δ-Bi2O3 particles/rod-like Bi4O7 composite with enhanced visible light-driven photocatalytic performance

In this paper, δ-Bi2O3/Bi4O7 heterojunction composites were successfully formed through hydrothermal reactions. The special morphology of rod-like Bi4O7 bonded with nanoparticles δ-Bi2O3 was observed by SEM and TEM, and BET results exhibited that the special surface area of the composite was increased slightly. The enhanced photocatalytic activity was mainly attributed to the construction of heterojunctions at the interface. Compared with two single phase samples, δ-Bi2O3/Bi4O7 exhibited much better photocatalytic efficiency in photocatalytic degradation of organic pollutants under visible light excitation. Especially, the composite BO-2 (the addition amount of δ-Bi2O3 was 0.25 mmol) showed the maximum removal rate for RhB (0.07275 min−1), which was 12.92 and 2.53 times that of δ-Bi2O3 and Bi4O7, respectively. Similarly, the composite showed an excellent removal rate (0.01042 min−1) for phenol, which was 13.71 and 1.77 times that of δ-Bi2O3 and Bi4O7, respectively. Further, TOC test confirmed that the mineralization ability of the composite was significantly improved with the successful construction of the heterojunction. Besides, the photocatalytic circulation tests showed the favorable stability of δ-Bi2O3/Bi4O7, and the trapping agent experiment verified the main active substances during photocatalytic, which were h+ and ·O2−. In addition, the electrochemical experiments results showed that the separation and migration ability of carriers was significantly improved due to the successful establishment of heterojunction. Consequently, a probable mechanism for organic contaminants degradation over δ-Bi2O3/Bi4O7 heterojunction was also proposed, which may spur a growth on Bi4O7 based heterojunction photocatalyst.