WHAT: Polymer electrolyte membrane fuel cells (PEM-FC) are under intense development for use in mass produced personal-use automobiles. Major targets for improvement are durability and reduction of amount of Pt catalyst. Polyfluoro sulfonic acids (PFSA), known as ionomers, are incorporated in the cathode and anodes of PEM-FC in order to provide proton transport. Optimizing the distriubtion and stability of the ionomer component improves durability and reduces the amount of Pt required. Together with researchers at the Automotive Fuel Cell Co-operation Corporation (AFCC), we have developed an efficient, quantitative method to map the critical ionomer component in the PEM-FC electrodes. By reducing the measurement to just four energies, it is possible to acquire high quality data over large areas with minimal radiation damage. When compared to analytical electron microscopy (using electron energy loss or Xray fluorescence), the method is better able to provide accurate information.

Figure: Color composite of quantitative maps of the carbon support (rblue), ionomer (green) and the Pt (red) in a PEM-FC cathode

OTHER INFORMATION: Publications relating to ionomer mapping in PEM-FC
D. Susac, V. Berejnov, A.P. Hitchcock, and J. Stumper, STXM Study of the Ionomer Distribution in PEM Fuel Cell Catalyst Layers, ECS Transactions 41 (2011) 629
D. Susac, V. Berejnov, A.P. Hitchcock and J. Stumper, STXM Characterization of PEM Fuel Cell Catalyst Layers, ECS Transactions 50 (2012) 405
A.P. Hitchcock, V. Berejnov, V. Lee, M.M. West, M. Dutta, V. Colbow and S. Wessel, Carbon corrosion of Proton Exchange Membrane Fuel Cell catalyst layers studied by Scanning Transmission X-ray Microscopy, J. Power Sources 266 (2014) 66