Characterisation of Nanocarbon-Based Gas Diffusion Media by Electrochemical Impedance Spectroscopy

A multi-wall carbon nanotubes (MWCNTs)-based gas diffusion medium (GDM) was prepared, where carbon black was partially substituted by carbon nanotube (CNT) in the formulation of the micro-porous layer (MPL). A rheological analysis of the ink used to coat the gas diffusion layer (GDL) was previously performed to correlate viscosities with the slurry composition. Shear thinning inks with viscosity of 0.4 (Pa s(-1)) were obtained for a composition containing 10 wt.-% of CNT and 12 wt.-% of fluorinated polymer. Using the doctor-blade technique, a coating thickness of about 100-150 mu m was obtained. Moreover, electrochemical performance of a single cell assembled with the CNT-based GDM was compared with that obtained with a sample without CNTs. In order to better understand the role of CNTs, electrochemical impedance spectroscopy (EIS) of the running fuel cell (FC) was also performed. As a result, it was found that the addition of CNTs sensibly improves single cell performances.