Surface and redox properties of cobalt-ceria binary oxides: on the effect of Co content and pretreatment conditions

Abstract

tCeria-based transition metal catalysts have recently received considerable attention both in heteroge-neous catalysis and electro-catalysis fields, due to their unique physicochemical characteristics. Theircatalytic performance is greatly affected by the surface local chemistry and oxygen vacancies. The presentstudy aims at investigating the impact of Co/Ce ratio and pretreatment conditions on the surface andredox properties of cobalt-ceria binary oxides. Co-ceria mixed oxides with different Co content (0, 20,30, 60, 100 wt.%) were prepared by impregnation method and characterized by means of N2adsorption at−196◦C, X-ray diffraction (XRD), H2temperature-programmed reduction (H2-TPR) and X-ray photoelec-tron spectroscopy (XPS). The results shown the improved reducibility of Co/CeO2mixed oxides comparedto single oxides, due to a synergistic interaction between cobalt and cerium. Oxidation pretreatmentresults in a preferential localization of cerium species on the outer surface. In contrast, a uniform distri-bution of cobalt and cerium species over the entire catalyst surface is obtained by the reduction process,which facilitates the formation of oxygen vacancies though Co3+/Co2+and Ce3+/Ce4+redox cycles. Funda-mental insights toward tuning the surface chemistry of cobalt-ceria binary oxides are provided, pavingthe way for real-life industrial applications.