Computational study of polymer membranes for proton and anion exchange membranes fuel cells

Abstract

Polymer electrolyte membranes with novel molecular architectures were simulated to study their structure-property relationships. Two types of polymer electrolyte membranes were considered: proton and anion exchange membranes. As a benchmark, Nafion, the most commercially successful membrane material, was simulated and subjected to mechanical deformation. The resulting water phase was found to be better developed in the direction perpendicular to deformation than in the stretched direction. Next, alternative hydrocarbon-based proton exchange membranes were designed and simulated. Polysulfone based membranes with typically exhibited smaller water domain sizes compared to Nafion. However, membranes with larger side chains and high sulfonation exhibited phase separation and transport properties comparable to Nafion. A polysulfone-based anion exchange membrane was compared to a proton exchange membrane with the same backbone. The two membranes exhibited similar phase-segregated morphologies, with significantly lower ionic transport in the anion exchange model. Last, a series of highly fluorinated multi-block copolymer anion exchange membrane were simulated and characterized. The simulations were validated by experimental structure and transport property trends. Design parameters to improve membrane performance and implications for future research are discussed.