Preparation and characterisation of cMWCNTs-mSA/mCS bipolar membrane for electrochemical synthesis

In this study, a bipolar membrane (BPM) of sodium alginate (SA) and chitosan (CS) was prepared based on carboxyl multi-walled carbon nanotubes (cMWCNTs). To improve the compatibility of anion-exchange layer and cation-exchange layer, polyvinyl alcohol (PVA) was blended with both the SA and CS, respectively. A casting method was employed to prepare the modified BPM named as cMWCNTs-mSA/mCS BPM for simplicity. The morphology, thermal and structure stability, electrochemical properties and ion penetrability of the BPM were characterised. Scanning electron microscopy (SEM) images illustrate a structure consisting of two distinct layers that are closely combined with each other. Thermal gravimetric (TG) results indicate that the thermal stability of cMWCNTs-mSA/mCS BPM is significantly improved. Swelling behaviour implies a proper hydrophilic performance and excellent structure stability in alkali solution. Compared with SA/CS BPM, the working voltage of cMWCNTs-mSA/mCS BPM is decreased sharply. Furthermore, the cMWCNTs-mSA/mCS BPM exhibited higher ion penetrability which is beneficial for electrochemical synthesis.