Cobalt and nitrogen co-doped porous carbon/carbon nanotube hybrids anchored with nickel nanoparticles as high-performance electrocatalysts for oxygen reduction reactions.

Non-precious metal-nitrogen-carbon (MNC) materials have been recognized as alternatives to noble-metal catalysts, such as Au/C, Pt/C and Ru/C. As the precursors of MNC catalysts, carbonized zeolite imidazole frameworks (ZIFs) have been widely studied due to their porosity and the composition of ligands, including carbon and nitrogen. Herein, we successfully synthesize a non-precious metal-based ORR catalyst with nickel nanoparticles anchored on cobalt and nitrogen co-doped porous carbon/carbon nanotubes (Ni/Co-NC), employing ZIF-67 metal-organic frameworks as precursors. The Ni/Co-NC catalyst shows an excellent onset potential of 0.984 V and a half-wave potential of 0.869 V in 0.1 M KOH, comparable to those of commercial Pt/C. The excellent ORR performance of Ni/Co-NC was attributed to the synergistic coexistence of the atomically dispersed metal species coordinated with nitrogen (metal-N sites) and carbon-encapsulated nickel nanoparticles as well as the hierarchical porous structure in the catalyst. In addition, the Ni/Co-NC catalyst possesses outstanding anti-poisoning capacity and long-term duration against methanol crossover in an alkaline environment. The obtained results enable the Ni/Co-NC catalyst to explore potential applications in energy conversion and storage systems.