Fatigue-Resistant Polymer Electrolyte Membranes for Fuel Cells

In a hydrogen fuel cell, an electrolyte membrane conducts protons, but blocks electrons, hydrogen molecules, and oxygen molecules. The fuel cell often runs unsteadily, resulting in fluctuating water production, causing the membrane to swell and contract. The cyclic deformation can cause fatigue crack growth. This paper describes an approach to develop a fatigue-resistant polymer electrolyte membrane. The membrane is prepared by forming an interpenetrating network of a plastic electrolyte and a rubber. The former conducts protons, and the latter enhances fatigue resistance. The introduction of the rubber modestly reduces electrochemical performance, but significantly increases fatigue threshold and lifespan. Compared to pristine plastic electrolyte, Nafion, an interpenetrating network of Nafion and perfluoropolyether (PFPE) reduces the maximum power density by 20%, but increases the fatigue threshold by 175%. Under the wet/dry accelerated stress test, the fuel cell with the Nafion-PFPE membrane has a lifespan 1.7 times that of a fuel cell with the Nafion membrane. The composite membrane with an interpenetrating network of a plastic electrolyte and PFPE rubber is fabricated by PFPE precursor diffusion into electrolyte membrane backbone and curing process. The membrane increases the fatigue threshold by a factor of 2.5 compared to Nafion membranes. In the fuel cell test, the composite membrane exhibits a lifespan of 1.7 times longer than Nafion membranes.image