Nitrogen-rich holey graphene for efficient oxygen reduction reaction

Abstract

Nitrogen (N)-doped porous carbon materials have attracted tremendous attention as low-cost and highly-efficient electrocatalysts for oxygen reduction reaction (ORR). In this study, holey graphene with a high edge pyridinic N-doping (43.0% in 5.1 at.% N, N-hG) has been prepared via a modified two-step synthetic method, involving the annealing in air at 430 °C to create holes, followed by N-doping in Ar/NH3 atmosphere at 850 °C. The resultant N-hG was demonstrated to possess a high specific surface area (1170.05 m2 g−1), outstanding ORR performance (E1/2 = 0.833 V, Eonset = 0.91 V) close to those of Pt/C catalyst in alkaline electrolyte, and a better long-term stability and methanol tolerance than Pt/C. The outstanding performance was attributed to the high specific surface area with abundant exposed active sites as well as the high edge N-content and large number of holes rich with the edge defects to ensure high catalytic activities. Furthermore, a mechanistic understanding of the hole formation in graphene lattice and subsequent edge N-doping was obtained, which could be used to guide the design and development of various new low-cost, highly efficient carbon electrocatalysts for ORR and beyond.