Facile Synthesis of Cobalt Nanoparticles Entirely Encapsulated in Slim Nitrogen-Doped Carbon Nanotubes as Oxygen Reduction Catalyst

Abstract

Owing to the scarcity of platinum resources and their visible flaw with poor durability and severe anode methanol crossover, Pt-based catalysts for catalyzing ORR have been experiencing some problems lately. Hence, nonprecious metal catalysts which are expected to replace platinum-based catalysts have become popular green sustainable development topics. We chose a facile pyrolysis method for the synthesis of this material, making the resulting coating material present a state of effectively encapsulating all cobalt nanoparticles into slim nitrogen-doped carbon nanotubes after process optimization, and the cobalt content even reached 20.9 wt %. In the catalytic aspect, the optimized Co@NSCNTs show a half wave potential equivalent to Pt/C in alkaline medium. Then, better durability (after 60,000 s chronoamperometry, the current retention still remains 95%) and commendable resistance to methanol crossover performed than the literature confirmed. All these characteristics superior to Pt/C should be ascribed to large amounts of entire encapsulated structures and synergism between encapsulated Co nanocrystal and graphitic N-doped carbon nanotubes. The presence of abundant metal particles allows more surface carbon and nitrogen atoms to be activated, in favor of the adsorption and dissociation of O 2, and then improving oxygen reduction reaction (ORR) catalysis.