(16b) Electrochemical Properties of Stainless Steel in Simulated Direct Methanol Alkaline Fuel Cell Environments

Direct methanol alkaline fuel cell (DMAFC) has potential advantages as compared to DMFC. It has been reported that improved methanol oxidation kinetics and restrained methanol crossover can be facilitated by using anion exchange membrane (AEM). In alkaline media, the conducting pathway of OH ions from the cathode to the anode is opposite to the direction of the electro-osmotic drag. Reduced methanol crossover will allow the use of higher concentration methanol, thus improving fuel cell performance. Bipolar plates are important components of a DMAFC. Metals can be used as bipolar plates having good chemical stability, electrical and thermal conductivity. They can be easily stamped to a desired shape to accommodate the flow channels. However, the corrosion of metal and the resulting metal ions can readily migrate to, and poison the membrane. The dissolved metal ions can lower the ionic conductivity of the membrane leading to poor performance. In this study, use of stainless steel (SS316L), a corrosion resistant metal, was investigated, in simulated DMAFC environments, by potentiodynamic and potentiostatic tests. The results indicated that the metal was mostly resistant to electrochemical corrosion. SEM with EDX scans after 4000s of potentiostatic tests, showed intergranular corrosion of the metal surface but corrosion on the cathode side was not so obvious. This investigation has shown that stainless steel can be effectively used in DMAFC fabrication.

Keyword Direct methanol alkaline fuel cell(DMAFC); Metal Bipolar Plate; Electrochemical Properties; Electrochemical impedance spectroscopy(EIS)

Acknowledgements The work was funded by the National High Technology R&D Program of China (2007AA05Z146, 2007AA05Z150) and Natural Science Foundation of China (50973055, 50911140287).