Highly Conducting and Stable Partial Fluorinated Polymer–Silica-Based Anion Exchange Membrane for Alkaline Fuel Cells

Abstract

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was defluorinated in the presence of alkali, and 4-vinyl benzyl chloride (VBC) was grafted by free radical copolymerization in the presence of an initiator to obtain PVDF-co-HFP-g-VBC. Then, 1-methylimidazole-tethered PVDF-co-HFP-g-VBC was synthesized for architecting the partial fluorinated anion exchange membrane (AEM). To improve essential membrane properties such as conductivity and ion exchange capacity (cation charge density), silica precursor 3-aminopropyl trimethoxysilane was incorporated in the polymer matrix. Prepared AEMs with different structural features were studied for morphology, ion-exchange capacity, water uptake, conductivity, and stability compared to other commercial AEMs. The reported PVIM-2.5-Si membrane, with quaternary ammonium and imidazolium groups, was resistant to alkaline degradation due to the nonavailability of β-hydrogen and negligible chance of nucleophilic (SN 2 ) attack. The suitably assessed PVIM-2.5-Si AEM shows 1.04 V open circuit voltage, corresponding to 294.15 mW cm −2 power density at 555 mA cm −2 current density, in an alkaline membrane fuel cell application.