Improved Fuel Cell Chemical Durability of an Heteropoly Acid Functionalized Perfluorinated Terpolymer-Perfluorosulfonic Acid Composite Membrane

Abstract

Commercial proton exchange membrane heavy-duty fuel cell vehicles will require a five-fold increase in durability compared to current state-of-the art light-duty fuel cell vehicles. We describe a new composite membrane that incorporates silicotungstic heteroply acid (HPA), α-K8SiW11O40▪13H2O, a radical decomposition catalyst and when acid-exchanged can potentially conduct protons. The HPA was covalently bound to a terpolymer of tetrafluoroethylene, vinylidene fluoride, and sulfonyl fluoride containing monomer (1,1,2,2,3,3,4,4-octafluoro-4-((1,2,2-trifluorovinyl)oxy)butane-1-sulfonyl fluoride) by dehydrofluorination followed by addition of diethyl (4-hydroxyphenyl) phosphonate, giving a perfluorosulfonic acid-vinylidene fluoride-heteropoly acid (PFSA-VDF-HPA). A composite membrane was fabricated using a blend of the PFSA-VDF-HPA and the 800EW 3M perfluoro sulfonic acid polymer. The bottom liner-side of the membrane tended to have a higher proportion of HPA moieties compared to the air-side as gravity caused the higher mass density PFSA-VDF-HPA to settle. The composite membrane was shown to have less swelling, more hydrophobic properties, and higher crystallinity than the pure PFSA membrane. The proton conductivity of the membrane was 0.130 ± 0.03 S/cm at 80˚C and 95% RH. Impressively, when the membrane with HPA-rich side was facing the anode, the membrane survived more than 800 h under accelerated stress test conditions of open-circuit voltage, 90˚C and 30% RH.

Investigation of Ionomer and Catalyst (Co3O4, Mn3O4, or MnO2) Interactions Using a Polyethylene Midblock Copolymer in Anion Exchange Water Electrolyzers to Understand Performance and Durability

“…The spectral range covered from 4000 to 800 cm⁻ 1 , and a liquid nitrogen-cooled MCT detector was employed for data collection. 32,38…”

A Critical Review of the Advancement Approach and Strategy in SPEEK-Based Polymer Electrolyte Membrane for Hydrogen Fuel Cell Application

“…HPAs act as a Bronsted acid toward the water molecules and thus increase the proton conductivity of the membrane. 281 HPAs are also used to increase the proton conductivity of SPEEK, but they tend to leach from the membrane due to their high solubility in water. Therefore, it is modified with other nanomaterials before being incorporated into the SPEEK matrix.…”

“…Heteropoly acids (HPAs), a type of inorganic fillers, are also used in PEM applications. HPAs act as a Bronsted acid toward the water molecules and thus increase the proton conductivity of the membrane . HPAs are also used to increase the proton conductivity of SPEEK, but they tend to leach from the membrane due to their high solubility in water.…”

Synthesis and Properties of Rubidium Salts of Phosphotungstic Acid

“…Rubidium salts of phosphotungstic acid (PTA) are one of the classes of heteropoly compounds that can be used in various fields, including the development of effective materials for electrochemical devices, such as fuel cells, gas sensors, and redox flow batteries [1][2][3][4][5][6][7][8][9][10]. Water-insoluble salts of PTA are widely used in organic catalysis [11][12][13], electrocatalysis [14], doping of polymer membranes [1,2,15,16], and various other fields due to an excellent combination of properties: high acidity, specific surface area (SSA), porosity, thermal stability, proton conductivity, and low solubility in water [17][18][19][20][21][22][23][24].…”