Catalytic performance and insight into the mechanism of CeO2 nanorod catalysts in phenol ozone oxidation reaction

Abstract

In order to effectively remove phenol wastewater and improve the utilization of ozone in non-homogeneous catalytic ozone oxidation, we synthesized cerium oxide catalysts with different morphologies and characterized the prepared catalysts. It was found that the dissolution/recrystallization rate was positively correlated with base concentration, with nanoparticles forming at low base concentrations. When the base concentration increases, the chemical potential to drive the anisotropic growth of the nuclei is higher, forming nanorods. At even higher concentrations of base, the nuclei are oxidized to have a nanocube morphology. The exposed surfaces of CeO2 nanorods and nanocubes are in the (110) and (100) planes, respectively, so they have a higher catalytic activity per unit surface area, this results in higher oxygen storage capacity and catalytic activity. The removal of phenol by ozone oxidation catalyzed by nr(nanorod)-CeO2 could reach 100% in a reaction of 30 min. The ESR technique demonstrated that ·OH, ·O2− and 1O2 produced during the reaction process are the main ROS that enhance catalytic ozone oxidation and participate in the degradation of phenol, which is decomposed into small molecule acids through substitution and ring opening reactions, and ultimately converted into CO2 and H2O. These results indicate that CeO2 nanorods exhibit stable and high performance in catalytic ozone oxidation, and controlling the morphology is an effective strategy to improve the catalytic performance.