Hydrogen crossover diagnosis for fuel cell stack: An electrochemical impedance spectroscopy based method

• Fuel cell electrode processes under potentiostatic conditions are analyzed. • An equivalent circuit model is developed to analyze impedance characteristics. • A novel hydrogen crossover diagnosis method based on EIS is proposed. Hydrogen crossover rate is a key parameter for characterizing internal gas leakage in proton exchange membrane fuel cells. Voltammetric and galvanostatic techniques are most commonly used in measuring hydrogen crossover. However, for the present, the existing methods have the drawbacks of being laborious and time-consuming. In this paper, electrochemical impedance spectroscopy is exploited for the first time to characterize hydrogen crossover in fuel cells. An equivalent circuit model is established based on comprehensively analyzing different electrochemical processes occurring on fuel cell electrodes. By comparing the measured impedance characteristics under various experimental conditions, it is found that a unique model parameter monotonically decreases with increasing hydrogen crossover rate. Accordingly, this single parameter is identified as the diagnostic indicator for hydrogen crossover. The effectiveness of the proposed method is validated on a single cell and a multi-cell stack. Our method allows deployment to each individual cell or multiple groups of cells in a fuel cell stack. Furthermore, one entire measurement by this method takes only 4 min, and the consumed time will not increase with the number of cells in the stack. It will provide a powerful tool for failure diagnosis and lifespan evaluation of fuel cell stack.