A bipolar membrane (BPM) was composed of a cation and an anion ion-exchange layer joined together in series. The water dissociation in BPM was then considered as an electric field-enhanced (EFE) phenomenon and its magnitude depended critically on the structure and composition of the bipolar intermediate layer. By changing the different content of ethanol

three commercial bipolar membranes Neosepta BP-1

Fumasep FBM and CJ-BPM were tested by AC impedance spectra and their bipolar membrane solvent resistance were evaluated simultaneously. It was confirmed that BP-1 had good solvent resistance and FBM and CJ-BPM solvent resistances were relatively weak. The experimental results showed that the water dissociation phenomenon occurred in the LiCl water-ethanol mixed solutions

and the local effective value of the BPM resistance increased with an increase in the content of ethanol

while the water dissociation became less obvious. This phenomenon could be explained due to the fact that the dissociative ability of alcohol was weaker than that of water. Thus

the existence of ethanol decreased the concentration of water in the intermediate layer of a bipolar membrane and caused the decrease in the water dissociation effect. By simplifying the algorithm to calculate the intermediate layer thickness of the BP-1 and FBM membranes

it was more intuitive to know the influence of ethanol content on the water dissociation.