It is of significant interest to produce metal-free electrocatalysts for oxygen reduction reactions (ORR) derived from low-cost and environmentally friendly biomass. This work presents a facile thermal annealing approach for large-scale synthesis of the nitrogen-doped graphene (N-GO) nanoflakes using melamine as the nitrogen source and chestnut shells-based biomass as the carbon source. This approach allows us to achieve a high nitrogen doping level in graphene. Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR) were used to characterize the N-GO. XPS analysis revealed the presence of pyridinic, graphitic, and pyrrolic nitrogen doping in graphene sheets, with pyridinic nitrogen being the most abundant. Electrochemical investigations showed that a higher concentration of pyridinic nitrogen configurations contribute significantly to the superior electrocatalytic activity toward oxygen reduction reactions (ORR) in alkaline electrolytes. The as-synthesized N-GO exhibits high ORR activity with the onset and half-wave potential of 0.90 V and 0.79 V in alkaline medium, respectively; which is among the best reported to the date for metal-free catalysts. Moreover, compared with the commercial Pt/C, optimized N-GO electrocatalyst exhibits more positive onset potential and better long-term stability, making it a promising metal-free catalyst for practical fuel cells.

Acknowledgements: The authors are thankful to Campus France and the National Research Foundation of Korea for financing the PHC Star mobility project (45823YC).