Efficient catalyst of defective CeO2−x and few-layer carbon hybrid for oxygen reduction reaction

Abstract

CeO2 nanomaterials are widely used as excellent catalysts for CO oxidation, tail gas purification and gas reforming, but they are rarely used in the oxygen reduction reaction (ORR). Here, a hybrid of few-layer carbon encapsulated defect-rich CeO2−x (CeO2−x@C), which was prepared by an direct-current arc-discharge process, is presented as a new efficient ORR catalyst. The defective structure of CeO2−x, involving oxygen vacancies and the presence of Ce3+, plays an important role on the ORR catalysis. Our CeO2−x@C achieves more positive onset potential (∼0.74 V), larger limited current density (∼6 mA cm−2) and an electron transfer number of ∼4, compared to the non-defective CeO2-carbon hybrid. Compared to the sample prepared via hydrothermal method, the CeO2−x derived from arc-discharge process has more uniform structure with surfactant-free surface, which may also contribute to the high ORR activity. Besides good ORR activity, our CeO2−x@C also shows excellent stability and good resistance to methanol crossover effects.