An Experimental Study of Humidity Distribution Dynamics in a Segmented PEM Fuel Cell

Abstract

An approach for local and transient in operando measurements of humidification along the channel of a segmented Proton exchange membrane fuel cell (PEMFC) is presented. Based on the impedances at fixed frequencies and temperature, equivalent relative humidity data is acquired and compared for steady state and transient experiments. Based on our results we can show that the classical 1kHz resistance in combination with a proper parametrization is a good choice for monitoring the ionomer humidification. A fast acquisition rate offers high resolution insights into the spatio-temporal dynamics of a PEMFC. It reveals that the current density and humidity distribution response to changes in stoichiometry and total current is highly inhomogeneous along the channel. The data is further used to establish a qualitative model that explains and predicts local dynamic phenomena occuring along the channel during local drainage or humidification.