ELECTROCHEMICAL EVALUATION OF BIS(TRIFLUOROMETHYLSULFONYL) METHANE AS A FUEL-CELL ELECTROLYTE

The kinetics of oxygen reduction on Pt were studied in a new type of perfluorinated acid, (CF3SO2)2CH2 [bis(trifluoromethylsulfonyl)methane], containing acidic C—H bonds. This acid appears to be the strongest carbene acid known. At 90°C, the conductivity of 1.15M (CF3SO2)2CH2 is 0.6Ω1 cm−1, which is the same as that of 98% phosphoric acid at 170°C. Even the room temperature conductivity of this acid is higher than that of 85% phosphoric acid at 100°C. Kinetic measurements were made using the rotating disk electrode technique in pH = 1 solutions and with porous fuel cell electrodes in solutions at the limit of solubility (1.15M). At pH = 1, the half-wave potential for oxygen reduction is shifted cathodically by 115 mV relative to that for phosphoric acid at the same pH, representing an approximately one order of magnitude increase in rate. Using standard fuel cell electrodes, the room temperature polarization in 1.15M (CF3SO2)2CH2 was 40–60 mV lower than with the same electrodes used in 85% phosphoric acid at 70°C. © 1990, The Electrochemical Society, Inc. All rights reserved.