New composite DMFC anode with PEDOT as mixed conductor and catalyst support

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The direct methanol fuel cell (DMFC) as electrochemical power source has attracted considerable attention due to its simple system design, low operating temperature, and convenient fuel storage and supply. Major limitations of the DMFC are related to the low power density, which is a consequence of poor kinetics of the anode reaction, poisoning of the catalyst by reaction intermediates, and methanol crossover. Research efforts have to address improvements of the anode catalyst structure and the ion-exchanger membrane. This project aims at the development of a new type of membrane anode assembly PEM*/PEDOT/CAT based on the conducting polymer PEDOT (Poly(3,4ethylene-dioxythiophene)) as catalyst support in combination with a new type of proton-exchange membrane (PEM*) with reduced methanol permeability. The designated catalyst (CAT) is Pt, Pt-Ru. This new system will be used with a conventional Pt/C cathode to manufacture membrane electrode assemblies (MEAs) to be tested in single cell experiments. Based on pervaporation membranes for separating water from alcohol, a new type of membrane (PEM*) with high proton conductivity and low methanol permeability is going to be developed. The application of PEDOT as mixed electronic/ionic conductor is expected to improve the charge transfer kinetics and the transport of protons and electrons within the anode structure leading to a better utilisation of the noble metal catalyst. Direct contact between the ion-exchanger membrane and the conducting polymer PEDOT will be achieved by a special polymerisation technique that has been developed for polypyrrole within the DFG priority programme 1060. The PEM*/PEDOT/CAT assembly will be characterised by electrochemical methods (CV, EIS, transient techniques), surface analysis (SEM, EDAX, TEM, XRD), and spectroscopy (IR, UV/Vis). MEAs employing the new anode structure and a conventional Pt/C cathode will be produced by screen printing. Tests in a single cell unit will serve to determine the current-voltage characteristics, the power density, the methanol turnover, the reaction products, and the methanol crossover. Modelling and simulation of transport processes and reactions taking place in the electrodes and in the complete cell will help to understand the performance and hence aid the experimental development of the new MEA.