Probing the Interaction between Nitrogen Dopants and Edge Structures of Doped Graphene Catalysts for the Highly Efficient Oxygen Reduction Reaction

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The N-doped carbon-based catalysts have emerged as potential alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR). Understanding the delicate interplay between dopants and graphene structures at the atomic level is crucial to rational designing high-performance carbon-based catalysts. Herein, we deeply explore the role of the edge structure of graphene, N doping configuration, position, and content in modulating the 4e – and 2e – ORR mechanisms using density functional theory calculations and comprehensively evaluate the ORR activity by combining the active site density and theoretical overpotential. We find that graphene with zigzag and armchair edges (G Z-A ) has extra spin density and high ORR activity compared to graphene with only armchair edges (G A-A ). The N doping position is more important than N doping content in improving ORR activity in N-doped G Z-A because only the proper N doping position, such as along the armchair edge, can increase the effective active sites by modulating the spin density. On the contrary, increasing N doping content is more efficient in boosting the ORR activity of N-doped G A-A since high N doping content contributes to the increased spin density and active site density. On the whole, N-doped G Z-A has a much higher turnover frequency (TOF) value than N-doped G A-A, and the G Z-A with pyridinic-N doping along the armchair edge exhibits the highest TOF value of 1.37 × 10 12 ( U = 1.23 V)/s –1 .