Development of Micro- to Macropores in Conductive Polymer-Based Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells

摘要

The aim of this work is to improve the porosity of gas diffusion layers (GDLs) for protonnexchange membrane fuel cell electrodes. These GDLs are made by twin-screw extrusionnprocess from conductive formulations composed of polyamide11 (PA11)/polystyrene (PS)nas the polymer matrix phase and an appropriate mixture of carbon black (CB) andngraphite (GR) as the conductive additives. Final GDL porosity, especially macroporosity,nwas generated by selective extraction of the PS phase using adequate solvents. Since thengeneration of pores was found to be directly related to blend morphology, several blendncompositions were studied and small amounts u00012–6 wt %u0002 of montmorillonite (MMT)nclay were used as compatibilizer to improve the dispersion of the PS phase inside thenPA11. It was observed that, although GDL volume porosity was not or slightly affected bynthe addition of MMT compatibilizer, its pore specific surface area was clearly increased.nFor GDLs made from a blend composed of 65 wt % of PA11/PS (30/70) and 35 wt % ofnGB/GR (57/43), an increase from 53 m2 /g (with no MMT) to around 75 m2 /g (withn2 wt % MMT) was obtained. This improvement within the addition of MMT was attributednto the modification of the dispersion state of PS phase. Such modification led to anhigher connectivity of pores and consequently more accessibility to the micro/mesoporesnof CB and GR. The major changes observed with the incorporation of MMT compatibilizernwere obtained for the small pore sizes (in the range of 10–400 nm). Depending onnMMT content, a considerable shift of pore size distribution in this range to smaller ornhigher values was obtained. Then the MMT compatibilization could be considered as anninteresting route to tailor GDL porous properties.