Diagnosis of a high temperature PEM fuel cell by electrochemical AC impedance spectroscopy

In this paper, the use of electrochemical AC impedance spectroscopy (EIS) for in-situ diagnosis of high temperature PEM fuel cells is described. EIS was performed on single cell hardware, built in-house, using a fuel cell test station modified to operate up to 120°C and 30 psig. Electrode kinetics, membrane resistance, porous-layer and mass transport impedance of MEAs, assembled in-house, were measured at various current densities for the purpose of validating the test station and cell hardware, and for optimizing MEA and flow-field designs. The effect of temperature and humidity on the various impedances was investigated. Impedances obtained at lower and higher temperatures were compared to obtain insight into the issue of water management in operating fuel cells.