Potential of montmorillonite nanoclay as water dissociation catalyst at the interface of bipolar membrane

Abstract

Bipolar membranes (BPM) containing montmorillonite (MMT) nanoclay interface as water dissociation catalyst was synthesized using sulfonated polyether-ether ketone (SPEEK) as cation exchange layer, while quaternized polysulfone as anion exchange layer. MMT nanoclay suspension in PVP solution was applied as interface layer, where MMT nanoclay loading were varied as: 0.25, 0.5, 1.0 and 2.0 mg⋅cm−2. Current-voltage (I-V) analysis with all synthesized BPMs containing MMT nanoclay showed lower water dissociation and transmembrane potential in comparison to that without nanoclay. This observation was justified by formation of charged sites in MMT platelets due to isomorphic substitution in alumino-silicate layers and availability of interlayer galleries in MMT nanoclay facilitated protonation-deprotonation steps of water molecules lowering dissociation potential. Based on I-V performance, BPM containing 1.0 mg∙cm−2 of MMT nanoclay (SBM-NC1.0) was chosen to evaluate its acid/base production rate separately using current densities: 250, 500, and 750 A∙m−2 and compared with BPM without nanoclay and FBM. Acid/base production rate increased with current density and MMT loading. Negligible change in potential drop (<0.05 V) with SBM-NC1.0 during 12 h of acid/base production at 500 A∙m−2 confirms its durability. Catalytic effect of MMT nanoclay for water dissociation at lower potential coupled with its appreciable durability and inexpensive nature are expected to make it a potential interface material for developing BPMs.