H2O2 Formation Mechanism in PEMFC

Abstract

The membrane degradation in a polymer electrolyte membrane fuel cell (PEMFC) has been believed to occur due to formation of H2O2 and its decomposition to radicals (·OH, ·HO2) in the presence of bivalent metal cations, which can be present as impurities in the membrane. This mechanism is mainly based on the study of H2O2 formation in the oxygen reduction reaction using rotating ring disc electrodes and ex-situ membrane degradation tests in Fenton's reagent. Whether the mechanism is consistent with the one in an operating fuel cell was investigated. Results indicate that H2O2 may be formed in the fuel cell in small amounts, but it is not the main source of harmful radicals and the membrane degradation. H2 and O2 seem to react directly on the catalyst in the electrode to form radical species, which degrade the membrane without formation of H2O2.