O-2 REDUCTION AT THE PT NAFION INTERFACE IN 85-PERCENT CONCENTRATED H3PO4/

The kinetics of oxygen electroreduction have been studied on a smooth platinum electrode coated with Nafion(R) in concentrated 85% H3PO4 The effects of Nafion(R) coatings of different thickness on O-2 electrore duction at a smooth Pt rotating disk electrode with 85% phosphoric aci d as the bulk electrolyte were examined. The kinetic current increases with increasing Nafion(R) film thickness while the diffusion limiting current decreases with increasing Nafion(R) film thickness. A O-2 con centration profile model for the Pt/Nafion(R)/bulk electrolyte has bee n established, and this model can be used to explain the O-2 reduction polarization results. The performance of Nafion(R)-modified, high sur face area Pt/carbon air cathodes for use in the H-2-air concentrated p hosphoric acid fuel cell was also studied. (C) 1998 Elsevier Science L td. All rights reserved.