Nonionic zeolite membrane as potential ion separator in redox-flow battery

Abstract The crystalline silicalite membrane has been demonstrated as an effective ion separator for acidic solutions of vanadyl sulfate and for potential application as a proton-permselective electrolyte membrane in the all-vanadium redox-flow battery. Silicalite contains uniform channels with an effective diameter of 0.56 nm, which permits the small H 3 O + ions to diffuse through but is impermeable to the large hydrated multivalent vanadium ions due to steric effects. Unlike conventional polymeric ion exchange materials, silicalite is nonionic and its proton conductivity relies on the electric field-driven H 3 O + transport through the sub-nanometer pores. The silicalite membrane exhibits high proton selectivity relative to vanadium ions and a significantly reduced self-discharge rate compared to that of Nafion ion exchange membranes.