Arunachalam Muthumeenal, Sinopoli Alessandro, Aidoudi Farida, Creager Stephen E, Smith Rhett, Merzougui Belabbes, Aïssa Brahim
Qatar Environment & Energy Research Institute (QEERI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha 34110, Qatar.
Department of Chemistry and Center for Optical Materials Science and Engineering Technology, Clemson University, 105 Sikes Hall, Clemson, South Carolina 29634, United States.
ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45935-45943. doi: 10.1021/acsami.1c10872. Epub 2021 Sep 17.
The deployment of alkaline anion exchange membranes (AEMs) in flow battery applications has the advantage of a low cationic species crossover rate. However, the alkaline stability conjugated to the low conductivity of hydroxide ions of anion exchange membranes (AEMs) still represents a major drawback for the large deployment of such technology. In this study, three types of tetraarylpolyphosphonium (pTAP)-based copolymers (namely, CP1, CP2, and CP3) are synthesized and blended with chitosan and polyvinylidene fluoride (PVDF) for the fabrication of AEMs. Chitosan, a green biopolymer, was employed as a blend to enhance the water uptake of the base ionomer matrix. It is proposed that the abundancy of hydroxyl groups in chitosan improves considerably the ionic conductivity, water transport, and ion selectivity of the membrane, together with facilitating the dispersion of the chitosan in the pTAP copolymer matrix. The purpose of blending PVDF is instead to provide stable mechanical strength to the composite blend. The chemical, mechanical, and thermal stabilities of the three fabricated composite-blend membranes (i.e., CM1, CM2, and CM3) were characterized. All the membranes exhibited a high water retaining capacity of up to 36.26% (recorded for CM2) along with a hydroxyl ion conductivity of 17.39 mS cm. Due to the strong interactions between pTAP copolymers, chitosan, and PVDF polymers (confirmed also by Fourier transform infrared spectroscopy), the studied anion exchange membranes are able to retain up to 97% of the original OH conductivity after 1 M KOH treatment at room temperature for 100 h. The three membranes, namely, CM1, CM2, and CM3, have vanadium ion permeabilities measured at 20 °C of 1.775 × 10, 1.718 × 10, and 1.648 × 10 cm/s, respectively, which are lower than that for the commercially available Nafion. The good stability and remarkable cell performance of the composite-blend membranes reported here make them definitely excellent candidates for the future generation of vanadium redox flow batteries.
碱性阴离子交换膜（AEMs）在液流电池应用中的部署具有阳离子物种交叉率低的优点。然而，与阴离子交换膜（AEMs）氢氧根离子的低电导率相关的碱性稳定性仍然是该技术大规模应用的一个主要缺点。在本研究中，合成了三种基于四芳基聚鏻（pTAP）的共聚物（即CP1、CP2和CP3），并与壳聚糖和聚偏氟乙烯（PVDF）共混以制备AEMs。壳聚糖是一种绿色生物聚合物，用作共混物以提高碱性离聚物基体的吸水率。有人提出，壳聚糖中大量的羟基显著提高了膜的离子电导率、水传输和离子选择性，同时促进了壳聚糖在pTAP共聚物基体中的分散。相反，共混PVDF的目的是为复合共混物提供稳定的机械强度。对三种制备的复合共混膜（即CM1、CM2和CM3）的化学、机械和热稳定性进行了表征。所有膜都表现出高达36.26%的高保水能力（CM2的记录值）以及17.39 mS/cm的氢氧根离子电导率。由于pTAP共聚物、壳聚糖和PVDF聚合物之间的强相互作用（傅里叶变换红外光谱也证实了这一点），所研究的阴离子交换膜在室温下用1 M KOH处理100小时后能够保留高达97%的原始OH电导率。三种膜，即CM1、CM2和CM3，在20℃下测得的钒离子渗透率分别为1.775×10、1.718×10和1.648×10 cm/s，低于市售的Nafion。本文报道的复合共混膜具有良好的稳定性和出色的电池性能，使其无疑成为下一代钒氧化还原液流电池的优秀候选材料。
