One-step synthesis of highly active cotton floc like ZnO-BiOI: Visible-light photocatalytic performance, recovery and degradation mechanism

As a new technology for wastewater treatment and new energy development, semiconductor photocatalysis technology has been widely studied in recent year. In this study, a series of ZnO-BiOI (1:1, 1:2, 1:3, 1:3, 2:1, 2:3, 3:1, 3:2) binary composite photocatalysts were synthesized by one-step solvothermal method. XRD, SEM, TEM, HR-TEM, UV-vis DRS and PL characterization methods were used to analyze the physicochemical properties. Compared with pure ZnO, the band gap of ZnO-BiOI composite was narrower, the light absorption ability was enhanced, and the photogenerated electron-hole recombination probability was reduced. Among all the samples, ZnO-BiOI (3:2) had the best activity to degrade RhB, and the degradation rate reached 98% after 240 min under visible light, and the first-order reaction rate constant was 34.8 times that of pure BiOI. In addition, ZnO-BiOI (3:2) showed good stability in the cycle experiment. The interfacial electric field was formed in the photocatalytic process of ZnO-BiOI (3:2), which promoted more photogenerated electron-holes to participate in the oxidation reaction. The degradation process of organic matter was mainly through the oxidation of center dot O-2(-) and h(+).