Binary and Ternary 3D Nanobundles Metal Oxides Functionalized Carbon Xerogels as Electrocatalysts toward Oxygen Reduction Reaction

A series of carbon xerogels doped with cobalt, nickel, and iron have been prepared through the sol–gel method. The doped carbon xerogels were further functionalized with binary and ternary transition metal oxides containing Co, Ni, and Zn oxides by the hydrothermal method. A development in the mesopore volume is achieved for functionalized carbon xerogel doped with iron. However, in the functionalization of carbon xerogel with ternary metal oxides, a reduction in pore diameter and mesopore volume is found. In addition, all functionalized metal oxides/carbon are in the form of 3D nanobundles with different lengths and widths. The prepared samples have been tested as electrocatalysts for oxygen reduction reaction (ORR) in basic medium. All composites showed excellent oxygen reduction reaction activity; the low equivalent series resistance of the Zn–Ni–Co/Co–CX composite was especially remarkable, indicating high electronic conductivity. It has been established that the role of Zn in this type of metal oxides nanobundles-based ORR catalyst is not only positive, but its effect could be enhanced by the presence of Ni.