Preparation Of Non-Precious Metals Hybrids And Their Electrocatalytic Performance Toward Oxygen Reduction Reaction And Oxygen Evoluton Reaction

Metal-air batteries possess many attractive merits such as high theoretical energy density, stable discharge voltage as well as environmentally friendly, its research and development received more and more concern at present. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are two key reactions in metal-air battery, but they both belong to the sluggish kinetics, led to the metal-air battery performance can not meet the requirements of practical use. Therefore, the research and development of ORR/OER catalysts which possess excellent performance, low price is a key step to promote its commercial application.Nowadays, transition metal oxides have attracted much attention due to their abundant reserve, low-cost, and good catalytic performance toward ORR and OER. In particular, the hybrids that consist of transition metal oxides and some other metal oxides have superior physical and chemical properties, which research and application in electric catalysis field are increasingly widespread. In this paper, by hydrothermal synthesis and subsequent heat treatment, transition metal oxide Co3O4 was respectively doped with SnO2 and Nb2O5, finally the Co-Sn-O mesoporous hybrids that comprised Co3O4 and SnO2 as well as the Co-Nb-O macropore hybrids that comprised Co3O4 and Nb2O5 were successful synthesised. Two types of hybrids were characterized with XRD, XPS, SEM and N2 adsorption-desorption, and evaluated their ORR and OER performance. The results showed both Co-Sn-O hybrids and Co-Nb-O hybrids exhibited excellent catalytic performance toward OER and ORR. As for Co-Sn-O hybrids catalysts, with Co:Sn ratio decreased, OER performance showed the law of first increase and then decrease. Among those, Co:Sn=7:3 hybrid catalyst exhibited best OER catalytic activity, its tafel slope is 64.1 mV·dec-1, the current density at 0.8 V is 10.729 mA·cm-2 and the electric potential value at 10 mA·cm-2 is 0.796 V; ORR performance showed the law of gradually decrease while Co:Sn ratio was decreased, therefor Co:Sn=10:0 hybrid catalyst displayed best ORR catalytic activity, its tafel slope is 66.7 mV·dec-1 and its initial voltage and half-wave potential (E1/2) are-0.062 V and -0.305 V, respectively. Among Co-Nb-O hybrids catalysts, with Co:Nb ratio decreased, OER performance showed the rough law of first increase and then decrease. Co:Nb=9:1 hybrid catalyst exhibited best OER catalytic activity, its tafel slope is 85.1 mV·dec-1, the current density at 0.8 V is 7.862 mA·cm-2 and the electric potential value at 10 mA·cm-2 is 0.816 V; ORR performance showed the law of gradually decrease while Co:Nb ratio was decreased. consequently, Co:Nb=10:0 hybrid catalyst displayed best ORR catalytic activity, its tafel slope is 65.8 mV·dec-1 and its initial voltage and half-wave potential (E1/2) are -0.077 V and -0.306 V, respectively.