Formation of N‐doped Graphene and Carbon Nanoparticles Integrated Composite for Efficient Oxygen Reduction Electrocatalysis

Abstract

AbstractN‐doped carbon‐based materials have been regarded as promising alternatives to Pt‐based electrocatalysts for the four‐electron (4e−) oxygen reduction reaction (ORR), which is an important electrochemical reaction for the polymer electrolyte fuel cells. Here, we report a N‐doped graphene and N‐doped carbon nanoparticles integrated composite electrocatalyst by a multi‐step acid etching plus annealing method. Despite the low N‐doping level, the material exhibits efficient 4e− ORR activity with an onset potential of 0.932 V, a half‐wave potential of 0.814 V, and a limiting current density of 5.3 mA cm−2 in 0.1 M KOH solution. We demonstrate that the promoted 4e− ORR activity is attributed to the special 2D–0D integrated structure for exposing massive active sites, the favorable porous structure facilitating the H2O transfer dynamics, and the high content of oxygen‐containing C−O−C species and the increased intrinsic carbon defects for additional active sites. A “decomposition and recrystallization” mechanism is proposed for the formation of N‐doped graphene.