Proton exchange membrane (PEM) fuel cells are being developed as alternative energy sources for both residential and automotive application. In order for this technology to become fully commercial, the reduction of cost and improvements in performance and durability of PEM fuel cells membrane electrode assemblies (MEAs) are still required. To address the requirement for further cost reduction the structure and composition of the cathode catalyst layer (CCL) has to be optimized in order to achieve optimum performance and durability while minimizing the PGM loading.

In order to rationally design CCL structures that meet the performance and durability requirements, a better understanding of structure versus performance relationships is needed. This requires the capability to fabricate different CCL structures, to characterize the spatial distribution of all phases within the catalyst layer1-3 (carbon, Pt, ionomer and void), to measure the physico-chemical properties (both ex-situ and in-situ) and finally to use these experimental data as inputs for the development a model based understanding of the relationship between CCL structure and CCL performance and durability.

Recently, significant progress has been made in the development of reliable measurement methods for key CCL properties such as thermal conductivity, electronic conductivity and gas diffusivity4-5. The dependence of these properties on CCL structure and manufacturing process provides support for rational CCL design.

References

1. J. Wu, A. P. Hitchcock, M. Lerotic, D. Shapiro, V. Berejnov, D. Susac, J. Stumper “4D imaging of polymer electrolyte membrane fuel cell cathodes by scanning X-ray microscopy”, Microsc. Microanal. 23 1784 (2017)

2. V. Berejnov, M. S. Saha, D. Susac, J. Stumper, M. M. West and A. P. Hitckcock: “Advances in Structural Characterization Using Soft X-ray Scanning Transmission Microscopy (STXM): Mapping and Measuring Porosity in PEM-FC Catalyst Layers” ECS Transactions 80(8) 241 (2017)

3. L. G. de Azeredo Melo, A. P. Hitchcock, J. Jankovic, J. Stumper, D. Susac and V. Berejnov: “Quantitative mapping of ionomer in Catalyst Layers by Electron and X-ray Spectromicroscopy” ECS Transactions 80(8) 275 (2017)

4. M. Ahadi, M. Tam, M.S. Saha, J. Stumper, M. Bahrami: “Thermal conductivity of catalyst layer of polymer electrolyte membrane (PEM) fuel cells: Part 1 – Experimental study” J Power Sources 354 207 (2017)

5. M. Ahadi, A. Putz, J. Stumper, M. Bahrami: “Thermal conductivity of catalyst layer of polymer electrolyte membrane (PEM) fuel cells: Part 2 – Analytical Modeling” J Power Sources, 354 215 (2017)