Effect of wet-proofing treatment of carbon backing layer in gas diffusion electrodes on the PEFC performance

Gas diffusion electrodes consisting of three layers, i.e., Pt/C catalyst layer (CL), hydrophobic gas-diffusion layer (GDL) and carbon backing layer (CBL), for polymer electrolyte fuel cells (PEFC) were investigated to clarify the relation between the electrochemical performance and the microstructure. We focused on effects of the GDL coating and the content of wet-proofing material (tetrafluoroethylene-hexafluoropropylene, FEP) in the CBL on the electrode performances with the constant composition of the CL. It was found that the hydrophobic GDL is effective to enhance the O-2 diffusivity and the catalyst utilization. A high performance due to high O-2 diffusivity was observed for the electrode by using the CBL without any FEP treatment at a relatively low air utilization operation. In contrast, the FEP treatment was found to be effective for the application to, for example, co-generation type fuel cells, which require the operation at relatively high potential and high utilization of air, e.g., 0.8 V and 40%.