Characterisation of fuel cell membranes using H₂-pumping operation

Proton exchange membrane fuel cells have been established as a viable technology to convert energy stored in a fuel, namely hydrogen, into electricity and heat. Especially for mobile applications this technology offers a number of advantages over other types of fuel cells, specifically a high power density and low operating temperatures. However, to facilitate proper conductivity of the membrane, the water content within needs to be maintained at a high level, balancing diffusion and electroosmotic drag within the membrane against one another and supplying water through humidified gas streams. This paper presents a methodology based on hydrogen pumping operation of membrane electrode assemblies to analyse the effect of different operating conditions on the membrane resistance. Further, in order to evaluate the electrochemical impedance spectroscopy (EIS) data obtained from the measurement procedures a post processing algorithm is used to filter noisy EIS data. Measurements are performed under fully humidified conditions at varying operating temperatures and at a fixed operating temperature using asymmetric humidification to study the influence of the electroosmotic drag. Surprisingly, no significant influence of the direction of the asymmetry is found.