Influences of CeO2 morphology on enhanced performance of electro-Fenton for wastewater treatment

Abstract

As a kind of rare-earth oxide, CeO2 has been considered as a great potential material for its abundant oxygen vacancies and catalysis activity in wastewater treatment. In this study, three ceria samples with different morphological structure were prepared, and their effect on contaminates degradation in electro-Fenton (E-Fenton) system was investigated. It is found that the morphology of CeO2 has great influence on promoting the performance of E-Fenton process. The rod-like CeO2 (R–CeO2) induced E-Fenton system shows higher azo dye X3B removal and mineralization rates than cubs (C–CeO2) and octahedrons (O–CeO2), and the degradation kinetic rate constants are 0.28, 0.169 and 0.181 min−1 respectively, already surpass that of the blank one (0.120 min−1). The H2O2 generation capacity of R–CeO2 induced E-Fenton system is also superior to the others, and the corresponding Faraday current efficiency even increases to 166.2% at 2.5 min. Characterizations by scanning-transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), Raman spectroscopy were conducted to disclose the mystery behind this phenomenon. The results indicate that the difference of surface oxygen vacancy density in different shaped CeO2 acts as a magic driving force for the accelerated oxygen reduction, and then leads to the enhanced degradation efficiency of E-Fenton system. This work provides a new insight into the development and application of rare-earth elements based catalyst in E-Fenton technology.