Electrical conductivity of PEMFC under loading

Conducting an experimental investigation, we show that the electrical conductivity σ (Sm−1) of the gas diffusion layer (GDL) and bipolar plates in stainless steel foam (SSF), as the heart of a Proton Exchange Membrane Fuel Cell (PEMFC), depends in fact strongly on mechanical compression arising in an operating system. Thus, this mechanical compression significantly affects the current density and σ; while it is not so far introduced in modelling and performance analysis. By mean of a developed metrology for this purpose and using Van der Pauw method, we studied, upon applied mechanical loads by varying the compression p, the electrical properties of different layers of a carbon cloth for GDL, of SSF, and, as in operating fuel cell, of the combination GDL + SSF in a sandwich form. A strong dependency is observed for each of these materials and their combination up to saturation for high enough p which is seen then to reduce the electrical resistance; while the number of layers has no influence. The obtained results are analysed in term of rate of increase of σ with an interesting conclusion for their application.