The effect of the gas diffusion layer on the performance of fuel cell catalyst layers in ethanol sensors

Abstract

The influence of the gas diffusion layer (GDL) on sensing performance of two commercially available fuel cell catalysts and membranes were investigated in an ethanol sensor. The catalyst used was either platinum black (Pt) or 20% platinum on carbon (Pt/C). These catalysts were coated onto a carbon paper, carbon paper with a microporous layer and carbon cloth GDL. Nafion and porous polyvinyl chloride (PVC) containing sulfuric acid were used as membranes. A fourth sample set with no GDL present was also tested. It was found the GDL’s effect on performance depended on the membrane electrode assembly (MEA) employed. For a Pt-Nafion MEA, the carbon cloth GDL showed the best performance compared to the other two GDLs and no GDL. The removal of the GDL significantly impacts the structural integrity of the catalyst layer, effecting performance. MEAs prepared with a carbon paper GDL were prone to localized flooding at higher humidity’s. Pt/C-Nafion MEAs showed similar performance, regardless of GDL. Removal of the GDL with a Pt/C catalyst greatly affected the structural integrity of the MEA, decreasing performance. PVC membranes are more flexible in the choice of GDL and catalyst layer. Overall, the carbon paper-MPL-Pt/C-PVC showed the best performance due to having the greatest stability in performance at the two humidities tested.