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

A novel 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 between steady state and transient experiments. Based on our results we can show that the classic 1 kHz 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. Our method reveals that the current density and humidity distribution responses to changes in stoichiometry and total current is highly inhomogeneous along the channel. Based on this compressive data, we were able to establish a qualitative model that explains and predicts local dynamic phenomena occurring along the channel during local drainage or humidification.