Effects of electrode compression on the performance of a solid polymer electrolyte fuel cell

Abstract

The effects of electrode compression on the performance of a polymer electrolyte fuel cell (PEFC) were investigated. Preliminary testing showed that considerable compression of the carbon cloth electrodes was provided by the PEFC structure. Further, the level of electrode compression was identified as a design parameter having a possible effect on the properties of the electrodes as well as the performance of the PEFC system. Performance-affecting properties of the carbon cloth electrode material, such as electrical conductivity and porosity, were determined over a range of compression levels. Compression was found to have a significant effect on the electrical conductivity and porosity of the carbon cloth electrode material, justifying further testing to measure the effects of electrode compression on PEFC performance. A new PEFC structure was developed which provided uniform mechanical pressure distribution over the area of the electrodes and allowed determination of the level of electrode compression. Utilizing this structure, several fuel cell systems were operated under various levels of electrode compression, and their electrical power output was measured using a linear-sweep voltammetry technique. Fuel cells of two different sizes using two different cathodic reactants--pure oxygen and air--were tested. Results of these experiments were plotted in a manner to illustrate the effect of electrode compression on PEFC performance. Electrode compression was found to have a significant effect on the performance of the PEFC systems observed in this investigation. A level of electrode compression was found for each fuel cell configuration which provided optimal performance. It was concluded from the findings of this work that the performance of PEFC systems utilizing porous carbon cloth electrodes is significantly affected by the level of compression placed on the electrodes. It was further concluded that an electrode compression level exists for PEFC systems which provides optimal performance under a given set of operating conditions.