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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.

Physically reinforced short-side-chain perfluorinated sulfonic acid electrolyte membranes were fabricated by annealing and using a porous support. Five types of solution-cast membranes were produced from commercial perfluorinated ionomers (3M and Aquivion (AQ)) with different equivalent weights, annealed at different temperatures, and characterized in terms of ion conductivity, water uptake, and in-plane/through-plane swelling, while the effect of annealing on physical structure of membranes was evaluated by small-angle X-ray scattering and dynamic mechanical analysis. To create a reinforced composite membrane (RCM), we impregnated a polytetrafluoroethylene porous support with 3M 729 and AQ 720 electrolytes exhibiting excellent proton conductivity and water uptake. The electrolyte impregnation stability for the porous support was evaluated using a solvent resistance test, and the best performance was observed for the 3M 729 RCM annealed at 200 °C. Both annealed and nonannealed 3M 729 RCMs were used to produce membrane electrode assemblies, the durability of which was evaluated by open-circuit voltage combined wet–dry cycling tests. The nonannealed 3M 729 RCM survived 5800 cycles, while the 3M 729 RCM annealed at 200 °C survived 16 600 cycles and thus exhibited improved mechanical durability.

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