Construction of Z-scheme ZnO/g-C3N4 photocatalytic systems for degradation of dyeing wastewater

A novel heterogeneous nanocomposite photocatalyst ZnO/g-C 3 N 4 was fabricated by secondary high-temperature calcination using g-C 3 N 4 and ZnO as raw materials and characterized by XRD , SEM , TEM, EDS , FT-IR, Zeta potential , UV-Vis and XPS . The results displayed that the ZnO/g-C 3 N 4 components were tightly bound, evenly distributed and significantly reduced in size, which could provide more active sites. The heterogeneous types, photocatalytic performance, degradation mechanism of ZnO/g-C 3 N 4 for dyeing wastewater were speculated by REDOX potential, heterojunction , and quenching experiments. The degradation efficiency of ZnO/g-C 3 N 4 on MB was much higher compared with that of single ZnO, g-C 3 N 4 and the mechanical mixture of ZnO and g-C 3 N 4 , which can reach more than 95% at 60 min. The degradation rate was also significantly improved, with the degradation rate exceeding 50% at 20 min. The composite ZnO/g-C 3 N 4 could degraded 90% MB after 5 cycles. The quenching experiment showed that hydroxyl (·OH) and photogenerated hole (h + ) played the main role in the reaction process. It was confirmed that the prepared ZnO/g-C 3 N 4 formed a Z-scheme photocatalytic system by examining the transfer paths of e - and h + in various types of heterojunction and contrasting the CB and VB energy levels with the REDOX potentials of ZnO and g-C 3 N 4 . The Z-Scheme ZnO/g-C 3 N 4 photocatalyst has the characteristics of stability, reusability, and no by-product, making it an ideal choice for environmental purification.