KCS

Direct alcohol fuel cells (DAFCs) that can run directly on liquid fuels such as methanol and ethanol bear several advantages over pure hydrogen/air polymer electrolyte membrane fuel cells (PEMFCs). However, investigation of the reaction mechanisms of alcohols in DAFCs is very difficult. We devised a new type of MEA from which a PEM can be extracted free from electrode components, such as catalysts, carbon black, and carbon cloth. Solid-state NMR investigation of this PEM, combined with solution-state NMR analysis of the exhaust, allowed studying the methanol and ethanol oxidations in direct DAFCs at close to the real operational conditions. The reaction intermediates such as formic acid and formaldehyde were directly observed in addition to methanol crossing over to the cathode through the PEM in direct methanol fuel cells. The reaction intermediates such as acetic acid and ethyl acetates were detected from the PEM in direct ethanol fuel cell. Surprisingly, the populations of the reaction intermediates found in the fuel exhausts were quite different from those observed in the PEM in the DEFC in terms of chemical identities and their relative concentrations. Implication of the findings was discussed in relation to the electro-catalytic reaction mechanisms and fuel cell performances in DAFCs. Supported by STRM program (C-Research-07-04-KBSI).