Synthesis of Co/CeO 2 hetero-particles with abundant oxygen-vacancies supported by carbon aerogels for ORR and OER.

It is highly significant for the fabrication of rechargeable metal-air batteries to develop cost-efficient and high-performance electrocatalysts of bifunctionality for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, we demonstrate a hybrid composed of CeO 2 -decorated Co nanoparticles supported on three-dimensionally porous carbon aerogels (Co-CeO 2 /C aerogels) as a superior bifunctional electrocatalyst. The preparation of Co-CeO 2 /C aerogels depends on the formation of a novel CeCl 3 /K 3 Co(CN) 6 -chitosan (CS) hydrogel, during which the cyanide groups of K 3 Co(CN) 6 combines the hydroxyls in CS by hydrogen bridges, accompanying with the substitution of chloride groups in CeCl 3 by cyanide groups in K 3 Co(CN) 6 . The electron spin resonance offers a convincing proof that numerous oxygen vacancies were found in Co-CeO 2 /C aerogels after the introduction of CeO 2 . The developed Co-CeO 2 /C aerogels showed an outstanding electrochemical performance for both OER and ORR in comparsion with RuO 2 and Pt/C catalysts in 0.1 M KOH solution. A small overpotential (380 mV) and a low Tafel slope (99 mV dec -1 ) were observed for OER, while the half-wave potential (0.75 V) and the onset potential (0.92 V) were high for ORR. The superior performance could be put down to the multihole heterostructure, multiple components and abundant oxygen vacancies. It was very helpful for the adsorption and the catalyzation of the reactants and the efficient mass transport of reagent/product. This work paves a neoteric method to synthesize a bifunctional hybrid catalyst with a highly efficient performance of energy conversion and storage.