(662a) Assessment of Dual Ion-Conducting Ceramic-Nafion Composite Membrane for Direct Methanol Fuel Cells

One important issue preventing the widespread commercialization of direct methanol fuel cells (DMFC) is that of complete fuel oxidation. Facilitating the oxidation of Pt-CO intermediates is essential for proper catalyst utilization. Some Nafion composite membrane studies focus on significantly reducing methanol permeability via addition of various inorganic oxides while attempting to maintain the high proton conductivity of Nafion.[1-3] The development of a Nafion composite membrane that addresses these key issues as well as that of CO poisoning of Pt catalysts would be extremely beneficial. This could be realized by allowing O2- species to be readily available at the anode catalyst via a highly effective dual-ion conducting membrane. Removal of the Pt-CO intermediates would thus proceed as

Pt-CO + O2- --> Pt(elemental) + CO2 + 2e-

A In0.1Sn0.9P2O7 solid state proton-conducting ceramic recently applied to intermediate-temperature fuel cell studies exhibits roughly 10% oxide-ion conductivity and likely contributes to enhanced CO tolerance when used as sole electrolyte in a DMFC at 170 oC.[4] The present study explores the creation of a continuous In0.1Sn0.9P2O7 matrix combined with recast Nafion films, with goals of observing reduced membrane resistance and enhanced fuel cell performance. The oxide-ion conductivity of the ceramic matrix provides increased CO tolerance at the anode in such systems due to direct CO oxidation.

A proof-of-concept composite membrane is formed by dip-coating a template with In0.1Sn0.9P2O7 and?-following proper activation of the ceramic?-subsequent addition of recast Nafion. The composite membrane structure will be tested at 90-130 oC to validate the improved CO tolerance, methanol crossover, and performance within a DMFC. Results for the composite will be compared against data obtained for the same membrane, sans In0.1Sn0.9P2O7.

(1) Yang, C.; Srinivasan, S.; Arico, A. S.; Creti, P.; Baglio, V.; Antonucci, V. Electrochem. Solid St. 2001, 4, A31-A34.

(2) Jung, D. H.; Cho, S. Y.; Peck, D. H.; Shin, D. R.; Kim, J. S. J. Power Sources 2003, 118, 205-211.

(3) Li, C.; Sun, G.; Ren, S.; Liu, J.; Wang, Q.; Wu, Z.; Sun, H.; Jin, W. J. Membr. Sci. 2006, 272, 50-57.

(4) Chen, X.; Wang, C.; Payzant, E. A.; Xia, C.; Chu, D. J. Electrochem. Soc. 2008, 155, B1264-B1269.