Proton Conducting Silica Immobilized PWA—PVDF Composite Membrane for AQS/BQDS Redox Flow Battery

Organic redox flow batteries (ORFBs) have attracted significant research attention as a large‐scale electrochemical energy storage system, credited to their adjustable properties, low cost, and availability of organic active materials. ORFBs are effective with low‐cost ion‐exchange membranes as the associated involved counter ion is only one type. In this work, we have synthesized a composite membrane by functionalizing polyvinylidene fluoride film with silica immobilized phosphotungstic acid and polyvinyl alcohol as binder for application in anthraquinone sulfonic acid (AQS), 4,5‐dihydroxy‐1,3‐benzenedisulfonic acid disodium salt monohydrate (BQDS) redox flow battery. The synthesized membrane was characterized by scanning electron microscope, x‐ray diffraction, and Fourier transform infrared spectroscopy. The membrane demonstrated comparable proton conductivity, and ion exchange capacity with that of Nafion‐115. The synthesized membrane was tested in single cell AQS‐BQDS flow battery. The synthesized anolyte (AQS) was characterized by using 1H‐NMR and UV‐vis spectroscopy. The single‐cell galvanostatic charge–discharge experiments were conducted at 5 mA cm −2 . The cell exhibited 98% of columbic efficiency and 60% voltage efficiency over 50 charge–discharge cycles. The present results demonstrated the suitability of the membrane for AQS‐BQDS flow battery application.