Co/N Co-doped Carbon Nanotube/Graphene Composites as Efficient Electrocatalysts for Oxygen Reduction Reaction

Cobalt/nitrogen co-doped carbon nanotube/graphene composites(Co/N-CNT/Gr-X, X represents the calcination temperature) were prepared by high temperature nitrogen doping with homemade graphene/N-methylpyrrolidone(NMP) dispersion and Co(NO₃)₂ as precursors. The results show that the solvent NMP in the graphene dispersion as a carbon source forms high-density carbon nanotubes on the surface of graphene with cobalt salt as catalysts, which provided a three-dimensional porous structure favorable for massive transfer of electrolyte ions. In addition, some cobalt ions were oxidized to form cobalt oxide and the others reacted with N to form a Co-N active site, thus leading to a markedly enhanced oxygen reduction reaction(ORR) performance. Among them, Co/N-CNT/Gr-800 exhibits a good performance in electrocatalytic activity, stability, and immunity towards methanol comparing with commercial carbon platinum(Pt/C) catalyst, the reduction potential and limiting current density of which were -0.137 V(vs. SCE) and 4.24 mA/cm², respectively. And the electron transfer number was 3.34.