Hydrothermal-microwave synthesis of cobalt oxide incorporated nitrogen-doped graphene composite as an efficient catalyst for oxygen reduction reaction in alkaline medium

The oxygen reduction reaction is a fundamental reaction in fuel cells to generate power, for which metal/metal-oxide carbon-based catalyst plays an important role. Herein, we report the hydrothermal-microwave synthesis of cobalt oxide incorporated nitrogen-doped graphene (Co3O4/N-rGO) composite and studied its catalytic potential for oxygen reduction reaction in alkaline medium. An energy dispersive X-ray analysis of Co3O4/N-rGO composite catalyst reveals ~ 3.1 at% nitrogen and ~ 4.3 at% cobalt content. The homogenous distribution of Co3O4 nanoparticles over the layered graphene sheets were observed from representative TEM images. The surface area of the catalyst was found to be significantly high (~ 344 m2/g), which provides surplus active sites for catalytic activity. The electrochemical activity of the synthesized catalysts carried through cyclic voltammetry were found to be in the order of Co3O4/N-rGO > Co3O4/r-GO > N-rGO > RGO. From the linear sweep voltammetry measurement (LSV), a noticeable positive shift in the half-wave potential and an enhanced limiting current is observed for Co3O4/N-rGO composite catalyst with an average electron transfer of 3.8 electrons, which is close to dominant four electron pathway of standard Pt/C catalyst. In addition, the Co3O4/N-rGO catalyst has demonstrated its higher stability in comparison with Pt/C catalyst in alkaline medium via LSV studies.