Suppression of Methanol Crossover and Distribution of Ohmic Resistance in Pt-Dispersed PEMs under DMFC Operation

Abstract

In order to suppress methanol crossover in direct methanol fuel cells (DMFCs), a new polymer electrolyte membrane (PEM) has been developed. Platinum nanocrystals were highly dispersed in a Nafion^® 117 film (Pt-PEM) to catalyze the oxidation of the crossover methanol with O2.O2. An appreciable increase in the cathode potential was observed, resulting from the reduced amount of methanol reaching the cathode. Distribution profiles of the specific resistance (ρ) in thickness direction were measured by using Pt probes inserted into the Pt-PEM under various operation conditions. Humidification of oxygen gas was found to be effective to achieve both uniform ρ distribution and high cathode performance. At a DMFC, Pt-Ru anode |Pt-PEM| Pt cathode, operated with 1 M CH3OHCH3OH and humidified O2O2 at 90°C, the terminal voltage at 200 mA/cm² was 0.41 V (IR-free) or 0.36 V (IR included). © 2002 The Electrochemical Society. All rights reserved.