Factors Influencing Electrochemical Properties and Performance of Hydrocarbon-Based Electrolyte PEMFC Catalyst Layers

Cathode catalyst layers (CLs) for proton exchange membrane fuel cells (PEMFCs) incorporating sulfonated poly(ether ether ketone) (SPEEK) solid polymer electrolyte were prepared and studied in a H(2)/O(2) fuel cell operated at 50 degrees C and 100% relative humidity. SPEEK-based CLs were found to exhibit higher protonic resistance, lower effective usage of Pt, and lower fuel cell performance compared to Nafion-based cathodes. A method of fabrication was developed to achieve a homogeneous distribution of SPEEK and polytetrafluoroethylene (PTFE) throughout the catalyst layer. Homogeneously prepared SPEEK-based CLs exhibited a higher electrochemically active surface area and lower protonic resistance but lower porosity and inferior water management compared to those prepared using a traditional two-step fabrication method, wherein SPEEK ionomer was impregnated into a preformed catalyst layer incorporating sintered PTFE and Pt/C. The choice of SPEEK electrolyte over Nafion was shown to adversely affect the bulk proton conductivity of the electrolyte inside the catalyst layer. This can be offset by increasing the SPEEK content in the catalyst layer but with the penalty of increased flooding and a larger resistance to gas transport.