DETERMINATION OF INTERNAL RESISTANCE AND ELECTROCATALYST UTILIZATION OF FUEL-CELLS

Analytical methods have been proposed recently for determining both th e internal resistance of fuel cell electrodes and the fraction of the electrocatalyst that is completely utilized. To apply these methods re quires that the Tafel slope and the equilibrium exchange current for t he electrolyte-electrocatalyst combination to be known when this combi nation is exposed to O-2 and when it is exposed to H-2. The Tafel para meters have been previously reported for O-2 and their measurement for H-2 is reported herein. Also, to apply one of these analytical method s maximum power method - requires that the current and potential to be measured when a fuel cell is operating at steady state and at maximum power. To apply the second method - approximate maximum power method - requires that the cell potential and slope of the potential versus c urrent curve be measured at a current that is less than that correspon ding to maximum power. To evaluate these methods, a series of porous c arbon electrodes were constructed, and to give them different resistan ces nickel was electro-deposited on the one side of each. These electr odes were then assembled into fuel cells and tested. Their internal re sistance was determined by the current-interrupt technique, and by usi ng the analytical methods. These results agree to within the experimen tal error, 12%. Electro-depositing nickel on the gas side of the elect rodes was found to decrease their internal resistance by an order of m agnitude and increase the electrocatalyst utilization by a factor of t hree.