Synthesis and characterization of a novel locally high dense sulfonated poly (aryl ether ketone sulfone) for DMFCs appli
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ORIGINAL PAPER
Synthesis and characterization of a novel locally high dense sulfonated poly (aryl ether ketone sulfone) for DMFCs applications Chengyun Yuan1 · Yinghan Wang1 Received: 2 July 2020 / Accepted: 3 September 2020 © The Polymer Society, Taipei 2020
Abstract A new sulfonated poly (aryl ether ketone sulfone) (SPAEKS-x) with locally dense sulfonic acid groups is synthesized by post-sulfonation. The SPAEKS-x membranes have a number average molecular weight of 45,000–58,000 g/mol and exhibit excellent mechanical properties. In addition, SPAEKS-x membranes have moderate water absorption, swelling rate, excellent thermal stability and good oxidative stability. The proton conductivity of SPAEKS-x membranes ranges from 35.6 to 52.4 mS/cm. All membranes show much lower methanol permeability than Nafion 117 membrane. Therefore, all membranes show higher proton selectivity than Nafion 117 membrane. In particularly, proton selectivity of SPAEKS-40 (15.8 × 104 S s cm−3) is about 5 times higher than that of Nafion 117 membrane (3.5 × 104 S s c m−3). Overall, SPAEKS-x membranes as a proton exchange membrane have shown very great application prospects in direct methanol fuel cells. Keywords Sulfonated poly (aryl ether ketone sulfone) · Proton exchange membrane · Fuel cell · Proton conductivity · Methanol permeability
Introduction With the increasing severity of environmental pollution and the urgent need for clean energy, fuel cells have received more and more attention due to their high energy conversion efficiency and cleanness. In addition to the general advantages of fuel cells, direct methanol fuel cells (DMFCs) also have a wide range of raw material sources and lowtemperature start-up characteristics, so they have received special attention. Proton exchange membrane (PEM) is one of the key components of DMFCs. It must have high proton conductivity, low methanol permeability, excellent oxidation resistance and mechanical properties. The most successful PEM that has been commercialized at present is the perfluorosulfonic acid membrane (such as the Nafion membrane produced by DuPont). The Nafion membrane has high proton conductivity, good mechanical strength, excellent thermal stability and chemical stability and it is widely used. However, it has some fatal flaws, such as extremely high cost [1], * Yinghan Wang [email protected] 1
State Key Laboratory of Polymer Materials Engineering, College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, China
severe reduction of proton conductivity at high temperature (> 80 ℃) and high methanol permeability [2]. Especially the high cost makes the large-scale use of Nafion membrane very difficult. In response to the problem, many researchers have developed a series of inexpensive non-fluorinated aromatic sulfonic acid membranes. They include sulfonated poly (aryl ether ketone) [3–9], sulfonated poly (aryl ether sulfone) [10–12], sulfonated polyimide [13–15] and sulfonated polybenzimidazole [16–18] and the like. In recent decades, researchers have
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