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 (Co 3 O 4 /N-rGO) composite and studied its catalytic potential for oxygen reduction reaction in alkaline medium. An energy dispersive X-ray analysis of Co 3 O 4 /N-rGO composite catalyst reveals ~ 3.1 at% nitrogen and ~ 4.3 at% cobalt content. The homogenous distribution of Co 3 O 4 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 m 2 /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 Co 3 O 4 /N-rGO > Co 3 O 4 /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 Co 3 O 4 /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 Co 3 O 4 /N-rGO catalyst has demonstrated its higher stability in comparison with Pt/C catalyst in alkaline medium via LSV studies.