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Although, the use of hydrocarbon membranes is one of the ways to reduce the cost of polymer electrolyte membrane fuel cells, it cannot be practically adopted due to its low mechanical durability under a dynamic wet/dry operation. Here, we present an externally-reinforced hydrocarbon membrane achieved by a three dimensional interlocking interfacial layer which forms a strong interfacial bonding between the hydrocarbon membrane and the catalyst layers. Although a conventional hydrocarbon membrane is easily delaminated from gas diffusion electrodes, the use of the three dimensional interlocking interfacial layer, prepared with a polystyrene nanoparticle template method, enhances the interfacial adhesion by 207 times. The hydrocarbon membrane, tightly connected to the gas diffusion electrodes by the three dimensional interlocking interfacial layers, has a humidity cycling durability that is 1.9 times higher in the membrane electrode assembly level by restricting the dimensional change of the membrane. Furthermore, due to the proton conducting property of the three dimensional interlocking interfacial layer, the external reinforcement does not cause any power performance losses.

The development of anion exchange membranes and ionomers plays a critical role in performance of anion exchange membrane fuel cells. However, the optimal design of catalyst layer structures still remains unexplored despite its significance. Herein, the rational design guide is presented for cathode and anode catalyst layers using m-TPN1 ionomer by controlling the size of ionomer aggregates in dispersion and comparing various catalyst layer structures. The size of m-TPN1 aggregates decreases, creating a more uniform ionomer distribution and a larger triple-phase-boundary. As ionomer distribution of the cathode catalyst layer becomes more uniform, the power density of membrane-electrode-assembly is enhanced. Also, the power density at fully humidified condition strongly correlates with the porosity of anode catalyst layer due to the limitation of hydrogen transport at anode by water flooding.

In this study, a new rugged catalyst layer (CL) structure is derived from a Nafion fiber mat to enhance the mass transport properties of polymer electrolyte membrane fuel cell. Nafion fiber mat is fabricated on a membrane surface by electrospinning technique and then a catalyst ink is sprayed on the fiber-coated membranes. With the Nafion fiber mat with 3.0 μm fiber diameter, a rugged CL supported on the fiber mat is formed, dictating the structural feature of the Nafion fiber mat. The resulting CL, which features an expanded outer CL surface, exhibits 21% improved power performance at 0.4 V under high humidity operation due to the increase of gas and water transport properties. These results demonstrate that Nafion fiber mat can be as an effective and scalable scaffold for the development of advanced CL.

H3PO4-doped polybenzimidazole (PBI) membranes have been employed for high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Although a thinner PBI membrane is beneficial in enhancing power performance, the use of thin PBI membrane has been hindered by its poor mechanical property and consequent difficulty in membrane handling during membrane electrode assembly (MEA) fabrication. Here, novel fabrication route to realize a thin PBI membrane (∼35 μm)-based HT-MEA is presented. The key feature of the process is to fabricate thin blend membrane of PBI and poly(ethylene glycol) (PEG) and laminate the blend membrane to anode gas diffusion electrode (GDE) followed by H3PO4 doping. The introduction of PEG to PBI film enables the tight bonding of the membrane to the GDE at a mild lamination temperature and mitigates the membrane expansion with the doping, preserving the tight interfacial bonding. Due to the lowered membrane thickness, the corresponding MEA exhibits a high power density of 264 mW cm-2 at 0.6 V. Therefore, the new fabrication strategy based on the blend of PBI/PEG is highly effective in improving both process and power performance of HT-MEA.

Ce-based materials have been widely used as a radical scavenger to improve the chemical durability of the membrane in polymer electrolyte fuel cells; however, any negative effects from Ce ions on power performance have not been reported as an issue before except for ionomer contamination by Ce3+. Herein, we propose and experimentally demonstrate the detrimental effect of Ce4+ on the Pt/C catalyst. Due to the strong oxidation power of Ce4+, Pt and carbon are subjected to oxidative decomposition under contact with Ce4+. Based on the electrochemical and spectroscopic analyses of the Pt/C stored in Ce3+ and Ce4+ electrolyte, Pt2+ dissolution and carbon corrosion by Ce4+ are verified. As a result, the active surface area and oxygen reduction reaction activity of Pt/C are considerably reduced after storage in the Ce4+ electrolyte. Additionally, at the membrane electrode assembly level, it is demonstrated that the Ce4+ leached out from the CeO2 causes a significant power performance decay along with the loss of the active surface area and an increase in the charge transfer resistance. The newly-found detrimental effect of Ce4+ on the Pt/C catalyst emphasizes the importance of preventing Ce4+ dissolution to improve the membrane durability by Ce-containing radical scavengers.