Nitrogen-rich carbon nano-onions for oxygen reduction reaction.

The demand for economical, sustainable and highly efficient catalysts to replace the Pt-based catalysts for proper industrialization of oxygen reduction reaction (ORR) has gained tremendous scientific interest. Herein, we report a facile strategy to develop doped nitrogen-rich carbon nano-onion architectures from the renewable biological resource, collagen, for use as a metal-free ORR catalyst. The product contains an appreciably high percentage of nitrogen (7.5%) integrated into the carbon molecular skeleton. The materials exhibit outstanding ORR electrocatalytic activity with low onset potential, high current density, superior methanol crossover immunity and better durability than the benchmark Pt/C catalyst in alkaline medium. The ORR followed an efficient direct reduction pathway of 4-electron transfer kinetics. The performance analysis of different samples demonstrates that the porous graphitic carbon with more nitrogen content provides adequate active catalytic sites for ORR activity and the pyridinic nitrogen act as an effective promoter for ORR. The findings ascertain that renewable biomasses can be easily transformed into novel carbon nanostructures with excellent catalytic activity. [ABSTRACT FROM AUTHOR]