Doped carbon nanomaterials as nonprecious metal catalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells have received intensive attraction.The improvement of ORR performance for the doped porous carbon nanostructures with high specific surface areas is mainly attributed to multi-doped electrochemical active sites provided by the metallic (Fe, Co) and non-metallic 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-/meso-porous structure, high crystallinity, and co-doping of metal and nitrogen.

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Direct ethanol fuel cells (DEFCs), which use ethanol as a fuel, have attracted considerable attention due to their relatively high energy density, the nontoxicity of ethanol, and the abundance of ethanol sources. However, since the crossover of ethanol as a fuel in DEFCs can deteriorate the cell performance due to the oxidation of ethanol (EtOH) at the cathode during oxygen reduction reaction (ORR), nonprecious metal (NPM) cathode catalysts for ORR have been studied using carbon-based nanostructures as promising alternatives to Pt-based catalysts. Herein, the doped carbon nanostructures (C/Fe-TMPP and C/Fe-Pc) as cathode catalysts were synthesized using a template method with iron(III) 5,10,15,20-(tetra-4-methoxyphenyl) porphyrin chloride (Fe-TMPP) and iron(II) phthalocyanine (Fe-Pc). In the half-cell test, C/Fe-TMPP exhibited an enhanced ORR activity in 0.5 M H 2 SO 4 (i.e., high half-wave potential and specific current density) and maintained ORR performance in the presence of crossover ethanol, compared to a commercial Pt/C. Moreover, C/Fe-TMPP exhibited high performance in the DEFC supplied with high-concentrated EtOH as a fuel at the cathode. The excellent ORR activity of C/Fe-TMPP for the DEFC can be attributed to ethanol tolerance in the ORR and low ethanol adsorption energy of the active sites for the ORR of C/Fe-TMPP.

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