Performance of PEFC formed by using Pt-loaded activated carbon under high- and low-humidity conditions

The enhancement of oxygen reduction at the catalyst layer formed from a Pt-loaded conventional activated carbon (Pt/AC) with adsorbed CF3SO3H compared to that from Pt/carbon black (Pt/C) was recently found using rotating disk electrodes (RDEs). In this study, we verified the enhancement at fuel cells formed by using Pt/AC carbon in the cathode catalyst layer. The layer was formed with various Nafion loadings to investigate its influence on the performance. The influence of humidity of the reactant gases was also investigated. It was found that the cathode formed from the Pt/AC required a higher Nafion content than the Pt/C cathode to produce the optimized performance. At a relative humidity of 100%, the polymer electrolyte fuel cell (PEFC) formed from Pt/AC showed better performance than that formed from the Pt/C in the cathodes. The adsorption of CF3SO3H onto Pt/AC further improved the performance. This tendency was in agreement with the results of the RDE measurements. At a relative humidity of 25%, although the hydrophilicity of the catalysts affected the kinetics of oxygen reduction and the cell resistance, the same tendency of the PEFC performance was observed. The results suggest the usefulness of Pt/AC with CF3SO3H for improvement of PEFC performance. (C) 2006 The Electrochemical Society.