Analysis of the Capacitive Behavior of Polymer Electrolyte Membrane Fuel Cells during Operation

Abstract

The interest in polymer electrolyte membrane fuel cells for automotive applications is nowadays increasing. To run such systems efficiently, the operating strategy relies on information about the stacks operational conditions. The cell capacitance, in most cases, contains such information and it can be measured in real-time using electrochemical impedance spectroscopy. However, the influence of the operating conditions on the cell capacitance is poorly understood so far. Therefore, this work analyses the influence of the oxygen content and cell voltage. Cyclic voltammetry and impedance spectroscopy data show equal hydrogen adsorption charges in oxygen-free operation. In oxygen-saturated atmosphere, the adsorption capacitance below 0.40 V is suppressed, probably owing to the fast adsorption of OH*. However, this allows distinction between the oxygen-free and oxygen-saturated conditions, as in the first case the total capacitance is significantly larger. Thus, an impedance-based operation strategy could detect oxygen undersupply in the fuel cells in real-time.