The Active Site Structure of Transition Metal Ion-Chelating Ordered Mesoporous Carbon Fuel Cell Catalysts

Transition metal ion-chelating ordered mesoporous carbons (TM-OMCs) were studied as polymer electrolyte membrane fuel cell cathode catalysts. The active site structure of the TM-OMCs was studied by X-ray absorption spectroscopy in combination with variations of a range of synthesis variables of the TM-OMCs. The variations were found to have significant influence on the catalyst structure both in the mesoscale and on the atomic local structure allowing for detailed conclusions on the nature of the active sites. The main active site was found to be FeNx chelates. An additional highly active site was found and proposed to be a FeNx-dioxygen site. It was further found that the catalytic activity could be increased threefold by acid washing and subsequent heat treatment of the as-synthesized TM-OMC materials.