Degradation Study of PFSA Polymer Electrolytes: Approach from Decomposition Product Analysis

Abstract

Fuel cell operation tests (I) and hydrogen peroxide vapor exposure tests with PFSA (perfluorosulfonic acid) polymer membranes (II) were carried out, and the decomposition products of PFSA polymer during the tests were examined mainly by NMR. (I) After OCV-hold and load cycling tests, we analyzed extracts from electrodes separated from a single cell, identifying six decomposition products in the extracts. The total amount generated from the OCV-hold test exceeded that generated from the load cycling test, as well as fluoride ion release rate (FRR). (II) Hydrogen peroxide vapor exposure tests at 90 and 100{degree sign}C under 3 humidity conditions were carried out with Nafion® 112 and Nafion® NRE-212. Decomposition products other than fluoride ions accounted for a significant portion of degradation weight loss, and their generation rates were not proportional to FRR, suggesting the presence of multiple PFSA degradation mechanisms.