Effect of micro-layer PTFE on the performance of PEM fuel cell electrodes

The function of gas diffusion layer in the fuel cell electrode is very critical as it acts as a current collector, facilitates the supply of reactants to the catalytic sites, and helps in removal of product water from the catalyst layer. In this paper attempts have been made to improve the dispersion of micro-layer by introducing an organic solvent. The electrodes were made by a screen printing method to improve the homogeneity of the gas diffusion layer. The main focus is on the effect of PTFE content in micro-layer using Ballard Avcarb 1071 carbon cloth as a substrate material. The percentage of PTFE on the substrate is kept constant in all the experiments, at about 18%. However, the percentage of PTFE in the micro-layer carbon is varied from 15 to 40 wt%. The micro-layer carbon loadingis about 3 mg/cm2 for all the electrodes. The Gurley number decreases with increase in concentration of PTFE in the micro-layer. The PEMFC cells were tested at 60 °C and at ambient pressure with relative humidity of hydrogen and air kept at 90% and 70%, respectively. The results were analyzed from the polarization curves. The DC resistances of the electrodes were correlated with concentration of PTFE in the micro-layer. The over potential values were also correlated with the Gurley number. The gas permeability, contact angle of the samples was measured and the results were correlated with performance of the PEMFC. The long-term stability of the electrode was recorded at fixed current density for various concentration of PTFE content in the micro-layer. The detailed results are discussed in this paper.