Bipolar membrane modified by cation/anion exchange nanofibers containing copper phthalocyanine derivatives with different substituents

Carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) and chitosan (CS)-polyvinyl alcohol were cross-linked by Fe³⁺ and glutaraldehyde respectively to prepare the cation exchange membrane layer and the anion exchange membrane layer, polyvinyl alcohol-sodium alginate (SA)-copper phthalocyanine tetrasulfonic acid (CuTsPc, or copper tetracarboxy phthalocyanine: CuTcPc) cation exchange nanofibers or polyvinyl alcohol-chitosan-copper tetraaminophthalocyanine (CuTAPc) anion exchange nanofibers prepared by electrospinning technique were introduced into the interlayer to obtain the modified bipolar membrane (BPM). The experimental results showed that in comparison with the BPM without the cation/anion exchange nanofibers interlayer, the water splitting efficiency of the modified BPM was obviously increased, and its membrane impedance decreased. When the concentration of CuTsPc in the PVA-SA-CuTsPc nanofibers was 3.0 %, the transmembrane voltage drop (IR drop) of the CMC-PVA/PVA-SA-CuTsPc/CS-PVA BPM was as low as 0.5 V at a high current density of 90 mA·cm^?2.