To elucidate the roles of the active oxygen Cycloheximide during the degradation of PTPB on the Bi12O17Cl2/β-Bi2O3 composite (sample S4), free radicals trapping experiments were carried out by adding various scavengers. Isopropanol was used to scavenge OH, sodium oxalate was used to scavenge photogenerated h+, potassium dichromate was used to scavenge photogenerated e−, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (TEMPOL) was used to scavenge O2−, and N2 was used to remove oxygen that was dissolved in the solution . As shown in Fig. 11A, after adding isopropanol, the photodegradation efficiency remained almost unchanged as no scavenger was added. However, a noticeable inhibition in the photocatalytic degradation was observed in the presence of potassium dichromate, TEMPOL, sodium oxalate, or N2, suggesting the significance of O2− and h+ in this photo-oxidation process. This possibility may be further confirmed by using the EPR method (Fig. 11B), which reveals strong DMPO-O2−-adduct signals after light irradiation. Therefore, the photocatalytic degradation of PTPB over the Bi12O17Cl2/β-Bi2O3 photocatalyst under visible light irradiation may be dominated by O2− radical (formed by the reaction of photogenerated electrons with dissolved oxygen) and directed hole oxidation instead of by OH oxidation, which may explain the high mineralization of PTBP in the system.