Insights into the Determining Effect of Carbon Support Properties on Anchoring Active Sites in Fe-N-C Catalysts toward the Oxygen Reduction Reaction

As one of the most promising non-noble metal electrocatalysts for the oxygen reduction reaction (ORR), previous investigations on Fe-N-C materials have mainly focused on the innovation of synthetic methods, identification of active sites, and structure optimization, but the intrinsic properties of carbon supports used to anchor Fe-N-x active sites have often been neglected. Herein, graphene oxide (GO) and reduced GO (rGO) are used as support models for heteroatom doping to prepare Fe-N-C catalysts. The obvious and easily distinguishable defects and the content of oxygen-containing functional groups in GO and rGO directly determined the doping content, structure type, and coordination environment of N and Fe. Notably, through analysis of the surface potential as a common parameter measured by Kelvin probe force microscopy, local work functions of these graphene-based catalysts at the nanoscale and their statistical averages were used to study the distribution of active sites and their association with ORR kinetics. This insight into the influence of carbon support structure properties on active sites and the work function-ORR performance relationship may provide guidance for exploring the origin of ORR activity and designing better non-noble metal electrocatalysts.