Anion Exchange Composite Membranes Composed of Quaternary Ammonium-Functionalized Poly(2,6-dimethyl-1,4-phenylene oxide) and Silica for Fuel Cell Application

Abstract

Anion exchange membranes (AEMs) with good alkaline stability and ion conductivity are fabricated by incorporating quaternary ammonium-modified silica into quaternary ammonium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO). Quaternary ammonium with a long alkyl chain is chemically grafted to the silica in situ during synthesis. Glycidyltrimethylammoniumchloride functionalization on silica (QSiO 2 ) is characterized by Fourier transform infrared and transmission electron microscopic techniques. The QPPO/QSiO 2 membrane having an ion exchange capacity of 3.21 meq·g –1 exhibits the maximum hydration number (λ = 11.15) and highest hydroxide ion conductivity of 45.08 × 10 –2 S cm –1 at 80 °C. In addition to the high ion conductivity, AEMs also exhibit good alkaline stability, and the conductivity retention of the QPPO/QSiO 2 -3 membrane after 1200 h of exposure in 1 M potassium hydroxide at room temperature is about 91% ascribed to the steric hindrance offered by the grafted long glycidyl trimethylammonium chain in QSiO 2 . The application of the QPPO/QSiO 2 -3 membrane to an alkaline fuel cell can yield a peak power density of 142 mW cm –2 at a current density of 323 mA cm –2 and 0.44 V, which is higher than those of commercially available FAA-3-50 Fumatech AEM (OCV: 0.91 V; maximum power density: 114 mW cm –2 at current density: 266 mA cm –2 and 0.43 V). These membranes provide valuable insights on future directions for advanced AEM development for fuel cells.

Ionic Triptycene Additive-Blended Poly(2,6-dimethyl-1,4-phenylene oxide)-Based Anion Exchange Membranes for Water Electrolyzers

“…After the quaternization, the halogen atomic-based chemical bonds (e.g., C–Cl wagging and C–Br stretching vibration modes from triptycene-Cl and BPPO, respectively) completely disappeared in the FT-IR spectra, indicating successful quaternization. Meanwhile, the FT-IR spectra of the QPQT- x blended membranes showed a new absorption band at 900–930 cm –1 due to the C–N + stretching peak (quaternary ammonium group). , Additionally, a broad absorption band at 3200–3600 cm –1 that was attributable to the O–H stretching vibration from the strong hydrophilicity of the quaternary ammonium group in the QPQT- x blended membranes appeared …”

“…49,50 Additionally, a broad absorption band at 3200− 3600 cm −1 that was attributable to the O−H stretching vibration from the strong hydrophilicity of the quaternary ammonium group in the QPQT-x blended membranes appeared. 51 The temperature-dependent weight loss was measured using a TGA instrument to understand the component amount through evaporation or degradation within a specific temperature range. Figure 3a shows the TGA curves of the QPQT-x blended membranes with various triptycene-Cl weight loadings (x = 0, 10, 20, and 30 wt %).…”

Imidazolium-Quaternized Poly(2,6-Dimethyl-1,4-Phenylene Oxide)/Zeolitic Imidazole Framework-8 Composite Membrane as Polymer Electrolyte for Fuel-Cell Application

“…Degradation of these imidazolium cation groups is due to Hofmann (or) E1 elimination reactions and nucleophilic substitution [2,25]. The conductivity of ImPPO and ImPPO/5%Zif exhibits an increasing trend for the first 30 h. This might be due to the KOH solution being confined inside the ionic channels of the two membranes, and the OH − ion could be better solvated in water and enhance the OH − transport via vehicular movement [33,34]. The conductivity of all the membranes drops over 120 h, but the ImPPO/5%ZIF-8 membrane was the most stable membrane, with more than 62% conductivity remaining after a period of 120 h. This might be due to the high amount of Zif-8 in the membrane matrix, and the Zif-8 seems to have an ability to solvate and bind the OH-to its network, thereby resulting in more enhanced alkaline stability and ImPPO/5%ZIF-8 having the highest amount of Zif-8.…”

Recent Developments on Bioinspired Cellulose Containing Polymer Nanocomposite Cation and Anion Exchange Membranes for Fuel Cells (PEMFC and AFC)

“…Thus the developments of a wide variety of quaternary ammonium functionalized polymers, such as poly(arylene ether sulfone), poly(arylene ether ketone), poly (p-phenylene-co-aryl ether ketone), poly(isatin biphenylene), poly(ether ether ketone), and poly(phenylene oxide) are considered for AFC applications [ 145 , 146 , 147 , 148 , 149 , 150 ]. Recently, several nano- or micro-fillers were tested in composite AEMs to improve the performance of AFCs even more [ 151 , 152 , 153 , 154 , 155 ]. In this connection, the surface-modified different bioinspired materials, specifically quaternized, have been developed to be evaluated in the AFC system with and without additives and other polymers.…”