In Situ Electrical Characterization of a High Temperature PEM Fuel Cell Stack At Loads

PEM fuel cells operated at temperature over 100°C has several advantages over traditional PEM fuel cells (generally operated at 80°C), including better reaction kinetics and higher CO tolerance. In this work, the Serenus fuel cell module was operated under ambient air and pure hydrogen at loads. The module contains a 65 planar cell stack with a nominal power around 1 kW. The area of each cell is ca. 285 cm². The operating temperature was varied from 140°C to 170°C and the current density was increased from OCV (open circuit voltage) up to 100 mA/cm². A small AC signal was superimposed on the fuel cell and the impedance data of the stack were collected by Gamry FC350 fuel cell monitor. The contributions of the different processes in the stack to the stack impedance have been mechanistically discriminated using the EC (equivalent circuit) diagram derived from the collected impedance. This work is useful for further study on kinetic mechanisms and cell performance of high temperature PEM fuel cells.