(244e) ZSM-5 Zeolite Nanosheet-Nafion Composite Membrane As an Ion Separator for Redox Flow Batteries

Zeolite nanosheets with nanometer-scale thickness and very large aspect ratios offer new opportunities to control crystal orientation and minimize thickness of zeolite-composite membranes for achieving enhanced selectivity and flux in molecular and ion separations. Here, we report the synthesis of a zeolite nanosheet laminated membrane (ZNLM) on polymer substrate and evaluation of this ZNLM-polymer composite membrane as ion separator for the vanadium redox flow battery (RFB). To enable the fabrication of ZNLM on polymer substrates, a room temperature UV-irradiation method has been established for template removal from the zeolite nanosheets that avoids the difficulty of zeolite activation after the composite membrane formation. The composite membrane fabrication is accomplished by synthesis of a ~350 nm-thick free-standing UV-activated ZSM-5 ZNLM, which is subsequently sandwiched in between two Nafion thing films to form a layered structure with an overall thickness of ~120 μm. This zeolite nanosheet-Nafion composite membrane exhibited drastically improved proton selectivity over the vanadium ions and reduced proton transport resistance as compared to the common benchmark Nafion-117 membrane. The composite membrane also exhibited higher Coulombic and voltage efficiencies in the all-vanadium RFB than the Nafion-117 membrane.