ZIF-8 derived C, N co-doped ZnO/Bi₂WO₆ Z-scheme heterojunction for photocatalytic degradation of methylene blue dye

C, N co-doped ZnO/Bi₂WO₆ Z-scheme heterojunction was successfully fabricated using ZIF-8 and Bi₂WO₆ as precursors. Its photocatalytic activity was evaluated through the degradation of methylene blue dye. The C, N co-doped ZnO/Bi₂WO₆ possessed a higher separation efficiency of photogenerated electron–hole pairs as suggested from PL, photocurrent response, and EIS analysis. The composite exhibited markedly improved photocatalytic performance, and the removal rate constant of MB achieved 0.0665 min⁻¹, which was around 4.26 times greater than that of C, N co-doped ZnO and approximately 10.2 times higher than that of Bi₂WO₆. Furthermore, the quenching test confirmed the participation of •O₂⁻, •OH, and ¹O₂ in the reaction, and ¹O₂ exhibited the dominant contribution to the photocatalytic activity. The ESR signals corresponding to three radicals were more pronounced in the presence of composite, which accounted for the enhanced photocatalytic activity observed in C, N co-doped ZnO/Bi₂WO₆.