Catalytic ozonation benefit from the enhancement of electron transfer by the coupling of g-C3N4 and LaCoO3: Discussion on catalyst fabrication and electron transfer pathway

Abstract

In this study, the novel design approach of catalyst in catalytic ozonation was proposed to enhance electron transfer in catalytic ozonation, achieving a better performance on micro-pollutants degradation and bromate elimination. The combination of perovskite oxide (LaCoO3, LCO) and graphitic carbon nitride (g-C3N4, CN) was studied to overcome some significant drawbacks of catalytic ozonation with metal oxides catalysts, such as the rate-limiting step between Men+ and Me(n+m)+. Additionally, the in-depth analysis of electron transfer pathway in CN/LCO catalytic ozonation was provided, which provided new insight into the design of highly efficient catalysts for facilitating micro-pollutants degradation and bromate inhibition. CN/LCO was successfully prepared and connected by the formation of -C-O-Co linkages, which exhibited a high activity in the catalytic ozonation for the synchronous degradation of benzotriazole (BZA) and elimination of bromate. Interestingly, being different with the general mechanism of catalytic ozonation, nitrogen vacancies and -C-O-Co bonds were the main active sites in CN/LCO rather than the surface hydroxyl group. With the largest amount of -C-O-Co and more nitrogen defects, CN/LCO exhibited a fast charge transfer along the in-plane direction. Additionally, the fast reduction of Co3+ to Co2+ was found to be initialized by O2•− and single electrons in catalytic ozonation, which resulted in more formation of H2O2 and good inhibition efficiency of bromate. This study not only present the good catalytic ozonation ability for refractory organic micro-pollutants and elimination of bromate using CN/LCO, but also provided insight into electron transfer pathway in the interlayers of CN/LCO, which will be significant for the design of catalyst and to promote charge transfer in catalytic ozonation.