Preparation and Characterization of Stable Ionomers and Ionomer Membranes for Fuel Cells

Abstract

Membranes based on sulfonated arylene polymers and their cross‐linked blends were prepared. Embedding the ionomers into textile or porous PTFE matrix and/or doping with ZrP nanoparticles reduced the swelling, and improved the thermal stability. PTFE reinforcement led to an excellent single cell performance, which is promising for PEMFC applications. Some of the membranes performed better than Nafion®. The net methanol crossover correlates with the membrane thickness and composition, but surprisingly, suppression of the methanol crossover alone, does not enhance U/I performance. ESR experiments of oxidative degradation of the monomer by OH• at pH > 10 leads to phenoxyl and semi‐quinone radicals. The study focuses on the case where O2•– or 1O2 are the damaging species, i.e. above pH 11.7, and the dominant reaction is that involving the aromatic ring. Under conditions of fuel starvation, the acid protons get depleted, which may lead to high local pH values, even in an overall acidic environment. It is therefore important to be aware of the entirely different form of degradation chemistry at high pH. In the presence of both HO• radicals and oxygen, complete degradation of the aromatic rings can be observed, within hours. In view of this, perfluorinated membranes are more inert. Cross‐linked arylene polymer blend membranes and PTFE‐reinforced arylene ionomer membranes can be regarded as promising for further development, due to their high stability and excellent PEMFC performance.

Oxidative and Photochemical Stability of Ionomers for Fuel‐Cell Membranes

“…, and comparing the coupling constants with literature values [15], it was concluded that the observed spectrum consists of five different, simultaneously appearing radical species with identical g values ( Table 3; details are reported in [20]). The fractions which are determined by matching the intensities in the simulation are 26% for radical 6, 14% for radical 7, 35% for radical 8, 17% for radical 9, and 8% for radical 10.…”

Durability of Sulfonated Aromatic Polymers for Proton‐Exchange‐Membrane Fuel Cells

“…[77][78][79] The results suggested that mechanical strength and thermal stability were improved to some degree. However, sufficient proton conductivity is still an important concern for cross-linked membranes with high mechanical and thermal stability.…”

Organic/Inorganic Nanocomposite Membranes Development for Low Temperature Fuel Cell Applications

“…Jiang et al, 2006a;Kuan et al, 2006; H.K. Mitov et al, 2006;Yang et al, 2001aYang et al, ,2001bYang et al, ,2004, SPEEK (Bonnet et al, 2000;Nunes et al, 2002;Silva et al, 2005b;Tchicaya-Bouckary et al, 2002;Triphathi et al, 2007Triphathi et al, ,2009, SPEK (Nunes et al, 2002;Ruffmann et al, 2003) and difulfonated poly(arulene ether sulfone) (Hill et al, 2006). A similar inorganic material derived from ZrP, named zirconium phosphate sulfophenylen-phophonate was also used as a filler with Nafion ® (Y.T.…”