Vanadium Oxide Nanosheet-Infused Functionalized Polysulfone Bipolar Membrane for an Efficient Water Dissociation Reaction.

Abstract

A high-performing bipolar membrane (BPM) was fabricated using functionalized polysulfones as the ion-exchange layers (IELs) and two-dimensional (2D) V2O5-nanosheets blended with polyvinyl alcohol (PVA) as the water dissociation catalyst (WDC) at the interfacial layer. The composite BPM showed a low resistance of 0.79 Ω cm2, confirming the good contact between the IEL and WDC, much needed for the ionic conductivity. It also demonstrated high water dissociation performance with a water dissociation voltage of 1.11 V corresponding to a current density of 1.02 mA/cm2 in the presence of a 1 M NaCl electrolytic solution. The functionalization of the polysulfone with -SO3- and R4N+ groups successfully resulted in the increase of hydrophilicity of the polymer, thereby increasing the water uptake capacity of the membranes. The blending of 2D V2O5 nanosheets with PVA proved to be an effective WDC, as confirmed by the increased conductivity and efficiency of the water dissociation (WD) reaction. The 2D V2O5-ns have great potential toward water adsorption onto its surface, thereby interacting with the water molecules, weakening the bonding force of water, and dissociating it into H+ and OH-. The transportation of coions across the membranes and generation of protons and hydroxyl ions at the interfacial layer are correlated with the change in the pH of the catholyte and anolyte as a function of current density during the WD reaction. The high performance of the composite BPM (BPM_VO-ns) was demonstrated at a higher current density of 100 mA/cm2 with a WD resistance of 0.027 Ω cm2. The durability was tested by subjecting it to 45 h of run at lower (1.02 mA/cm2) and higher (100 mA/cm2) current densities which display a negligible change in the interlayer voltage. Thus, the fabricated composite BPMs pave the way to be utilized for efficient and durable WD reactions under neutral electrolytic conditions.