Ultra-High Ion Selectivity of a Modified Nafion Composite Membrane for Vanadium Redox Flow Battery by Incorporation of Phosphotungstic Acid Coupled UiO-66-NH2

An ultra-high ion-selective Nafion composite membrane for vanadium redox flow battery (VRB) by incorporation of phosphotungstic acid (PWA) coupled UiO-66-NH2 was prepared through solution casting. Simple tuning for the filling amount of the nanohybrid composed of PWA and UiO-66-NH2 gives the obtained membranes preeminent vanadium barrier property including a minimum vanadium permeability of 3.46 x 10(-7) cm(2) min(-1) and excellent proton transport capability including a maximum proton conductivity of 0.092 S cm(-1) at 25 degrees C. These indicate an ion selectivity of 2.66 x 10(5) S min cm(-3), showing an overwhelming advantage over recast Nafion (0.34 x 10(5) S min cm(-3)). As a result, the VRB constructed with the modified membrane exhibits superior battery performance versus recast Nafion at various current densities.