Electro- and physicochemical analysis of catalyst coated membranes

Cost-effective production of catalyst coated membranes (CCM) is one of the key challenges for the successful realisation of fuel cell stacks ready for commercialisation. It represents the core component of the membrane electrode assembly, which is the centrepiece of the fuel cell repeating unit. The most plausible ways to achieve reasonable fuel cell unit price per kilowatt installed, are increasing cell performance and reducing material costs of the most cost-intensive part of the system; the cathode. Recently, the content of expensive platinum in the cathode catalyst was reduced, while simultaneously increasing the activity towards the oxygen reduction reaction by using binary PtM - systems (M = Co, Ni, Cu, e.a.) as active particles on the carbon support. Reproduction of these promising results at single cell level has only been partially achieved, owing to the complex interactions between solid electrolyte (ionomer), reactant gases and catalyst. The lack of reproducible means of membrane electrode assembly preparation is adding up to the challenge.
Automated CCM production, allows the detailed and reproducible experimental analysis of interactions between catalyst, ionomer and reactant gases. PtCu3/C and Pt/C with three different carbon-to-metal ratios are used to prepare cathode active layers with varying structure. TEM images of the pure catalyst and SEM/EDX of CCM cross sections are recorded to obtain structural information. Additionally, electrochemical impedance spectroscopy (EIS), polarisation curves and cyclic voltammetry supply the information needed to study the influence of the catalysts physical- and chemical structure on fuel cell operation and in-situ catalyst activity.