Study of Polymer Electrolyte Membrane Degradation under OCV Hold Using Bilayer MEAs

Abstract

Accelerated degradation tests for polymer electrolyte membrane fuel cells are frequently conducted under open-circuit voltage (OCV) conditions at low relative humidity and high temperature. Comparative experimental studies were carried out to identify the localization of membrane degradation through the thickness direction of the membrane under the OCV hold condition and the effect of platinum band location on the membrane degradation behavior. A bilayer configuration of the membrane electrode assemblies (MEAs) was used for this study. In one test, the fuel cell with the bilayer MEA was exposed to hydrogen and air (regular test); in another test, the bilayer MEA was exposed to 4% hydrogen (balance nitrogen) and pure oxygen to induce the platinum band formation close to the anode side. Hydrogen crossover current, electrochemical areas (ECAs), and polarization curves were evaluated pre- and post-test. After the OCV hold test, the bilayer MEA was separated into two pieces of one-side coated membranes; each piece was characterized by uniaxial mechanical testing, IR spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDS) analysis. The findings suggest highly localized degradation or a defect band formed through the thickness direction of the MEA, and the defect band shifts with the shift of the Pt band.