Preparation, ex situ and in situ Characterization of Gas Diffusion Media Containing and Non-Containing Carboxymethylcellulose for PEM Fuel Cells

In this paper the effect of the addition of carboxymethylcellulose (CMC) to microporous layers (MPLs) formulation is reported and the rheological, morphological and electrical properties of the so-obtained MPLs are assessed. Two different PTFE/carbon black ratios are considered, with and without CMC in the ink formulation. CMC addition results in a better homogeneity and stability of the inks. Moreover, the presence of CMC leads to a better shear thinning behaviour and to a general increase in viscosity that makes these slurries more appropriate for coating deposition via doctor blade technique. The presence of CMC in MPL formulation also affects the electrochemical performances in terms of I–V curves and impedance spectra. CMC-containing MPLs show the best performances in terms of generated power at high temperature (80 °C) and low cathodic relative humidity (RH 60 %). Ohmic resistances too, in presence of CMC, are lower than those exhibited by CMC-free MPLs.