Bimodal Porous Iron/Nitrogen-Doped Highly Crystalline Carbon Nanostructure as a Cathode Catalyst for the Oxygen Reduction Reaction in an Acid Medium

Abstract

Doped carbon nanomaterials as non-precious-metal catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells have received intense attraction. The improvement of ORR performance for the doped porous carbon nanostructures with high specific surface areas is mainly attributed to multidoped electrochemical active sites provided by the metallic (Fe, Co) and nonmetallic species (N, B, and S). Here, we prepared porous iron/nitrogen-doped carbon nanostructured materials via a simple synthesis process using silicate beads (500 and 50 nm diameter) as templates in the presence of 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin (TMPP) or (5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin)iron(III) chloride (FeTMPP). The resulting samples exhibited a bimodal porous structure, homogeneous heteroatomic doping, and a fairly large specific surface area. In particular, the sample prepared using both 500 and 50 nm silicate beads with FeTMPP (FeTMPP-C-500/50) exhibited much improved ORR performance in an acid solution. The enhanced ORR properties of FeTMPP-C-500/50 could result from the fairly large specific surface area, mixed macro-/mesoporous structure, high crystallinity, and codoping of metal and nitrogen.