Unraveling the catalytic ozonation mechanisms with ZnO decorated rGO composite: Structural properties and reactive oxygen species evolution

Abstract

In this study, a series of ZnO decorated rGO composites (x%ZnO@rGO) were successfully synthesized by the alkaline hydrothermal method. The crystal structure, surface morphology, and chemical property of x%ZnO@rGO were characterized by BET, XRD, FT-IR, SEM, TEM, and XPS, respectively. Amongst, 15%ZnO@rGO composite exhibited superior catalytic ozonation performance with an improvement of 68.4% on atrazine (ATZ) degradation efficiency (3 mins), more than 7.8 times of the pseudo-first-order rate constant compared with single O3. The roles of O3 and reactive oxygen species (ROSs) were confirmed and compared by the quenching and low-concentration probe experiments, suggesting that O3 and OH played an important role for ATZ degradation, while the function of 1O2 and O2− can be neglected both in single O3 and 15%ZnO@rGO/O3 system, which was contrary to that of the quenching experiments. Besides, the exposures of O3 and ROSs showed that 15%ZnO@rGO can facilitate the transformation process of 1O2 to OH in different conditions, and largely enhance the exposure of OH. The roles of electrons, Lewis acid sites, and oxygen vacancies of 15%ZnO@rGO in catalytic ozonation were identified as well, which offered us a new perspective to design a high-efficiency catalyst and may promote graphene-based metal oxides for practical pollutant elimination.