Abundant Ce–O–C Defects Promote the Formation of Single-Component CeO<sub>2</sub>C<sub>2</sub> Bifunctional Electrocatalysts for the Oxygen Reduction Reaction
Guandong Wang, Wenjuan Xiang, Huize Liu, Yizhi Yin, Dandan Ma, Jinfu Ma
Abstract
The key to the development of metal–air batteries is the research on efficient and stable non-noble metal bifunctional electrocatalysts that can simultaneously catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the same electrolyte. Ce–O–C single-component materials have abundant oxygen vacancies and commendable electrical conductivity; therefore, they have great application potential in bifunctional catalysis. However, their application is limited by the harsh synthesis conditions (pyrolysis at >1750 °C). Herein, CeO 2 C 2 /NC material is obtained during the pyrolysis of Ce-MOF at 900 °C, and it is found that the CeO 2 C 2 /NC material has a satisfactory ORR/OER bifunctional catalytic effect. In addition, CeO 2 C 2 /NC possesses good electrochemical properties, such as ORR E onset = 0.92 V, E 1/2 = 0.83 V (vs reversible hydrogen electrode (RHE)), and an excellent Tafel slope of 77.7 mV dec –1, outperforming the commercial Pt/C catalyst. X-ray photoelectron spectroscopy (XPS) analysis reveals that Ce 3+ and its chemisorbed oxygen (O β ) percentages of 50.33 and 79.37%, respectively, are the main reasons for the production of abundant oxygen vacancies. The prepared Ce–O–C series material will be applied to zinc–air batteries (ZABs), which is expected to improve the comprehensive performance of ZABs. The results can provide ideas for the development of ORR/OER single-component bifunctional catalysts.