Influence of the Distribution of Platinum Deposits on the Properties and Degradation of Platinum-Impregnated Nafion Membranes

Abstract

In proton exchange membrane fuel cells (PEMFCs), platinum (Pt) from the electrodes can be deposited in the electrolyte membrane, altering its properties and causing degradation. To investigate these impacts, in some studies, membranes with artificially deposited Pt were used, however, with contradictory results. In this study, we compared membranes impregnated with 0 to 4.4 wt% Pt. Specifically, the Pt particle distribution and mass transport in the membrane as well as the membrane decomposition is investigated after performing open circuit durability tests for∼140 h. The properties of the membrane electrode assemblies (MEAs) are studied by electrochemical characterization. The changes upon degradation are investigated by thickness determination, infrared spectroscopy, fluoride emission, hydrogen permeability, and electrical conductivity. Our investigation confirmed that the particle density, not the Pt amount, is the determining factor in the extent of membrane decomposition: fluoride emission decreased exponentially with particle density. We further found a considerable difference in the particle distribution between artificial and in-situ Pt deposits. Moreover, properties of both membrane types changed contrary to each other during the durability test. In conclusion, Pt-impregnated membranes do not reflect the state of degraded membranes with in-situ formed deposits but are suitable to investigate the influence of particle distributions.