This work reports on the compression dependent characterization of the GDL morphology, mass and energy transport by means of X-ray tomographic microscopy (XTM) and numerical transport simulations of SGL 24 BA material. X-ray tomographic microscopy images were recorded with a 2.2 um voxel edge length. Though the pores in the binder are not resolved with such voxel dimensions, a specific segmentation procedure of the reconstructed images makes possible to distinguish between fibres, binder and void (see Figure 1, left). The porous binder domains are identified as stiff GDL component, as the volume of the binder domain remains constant for compression levels between 0 – 25 % (see Figure 1, right). In this compression range only the volume of the identified void domain reduces, the fibers deform but the binder domains are not affected. For compression levels above 25 % the binder starts to be compressed and the volume of the binder domains reduces similar as the overall GDL volume. Comparing numerical transport simulations with experimental GDL effective diffusivity and conductivity data, the binder effective transport parameters are determined for different compression levels.
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Figure 1: Left) 3D rendering of a ternary segmented SGL 24BA gas diffusion layer at 0 % compression ; green: fibres, red: binder, white: void; Right) relative volume fractions of the components of the ternary segmentation as function of compression.