ANALYTICAL METHOD FOR DETERMINING THE INTERNAL RESISTANCE AND ELECTROCATALYST UTILIZATION OF FUEL-CELLS

Two analytical methods are developed that each allows one to determine : (i) the internal resistance of fuel cell electrodes, and (ii) the fr action of the electrocatalyst that is effectively used. To apply eithe r method requires knowledge of the Tafel parameters for the electrocat alyst-electrolyte combination. In addition, one method - the maximum p ower method - requires that the potential and current of a fuel cell b e measured when the cell is operating under steady-state conditions an d at maximum power. Thus, its application is limited to fuel cells tha t are not damaged by operating at these conditions. The second method is approximate, but it does not require that the voltage and current b e measured at the maximum power condition. To apply the second method - approximate maximum power method - requires the measurement of the f uel cell potential and slope of the potential-current relation of the fuel cell at a current that is less than the current corresponding to the maximum power condition. Using data available from the literature, the two techniques are used to evaluate these characteristics for a K OH fuel cell. They are also used to predict the voltage-current relati on for the fuel cell. The results are found to be in close agreement w ith the reported measurements over a range of currents. The range is l arger for the 'maximum power method' than for the 'approximate maximum power method'.