Preparation and characterization of mSA/mCS bipolar membranes modified by CuTsPc and CuTAPc

In this paper, sodium alginate (SA) and chitosan (CS) were modified by copper phthalocyanine tetrasulfonic acid (CuTsPc) and copper tetraaminophthalocyanine (CuTAPc) respectively to prepare the CuTsPc-SA/mCS bipolar membrane (BPM) and the mSA/CuTAPc-CS BPM (here, mCS and mSA indicate the CS anion exchange layer and the SA cation exchange layer modified by glutaraldehyde and Fe3+ as linking reagents, respectively). Experimental results showed that the ion exchange capacities and the ion transmigration rates of the CuTsPc-SA cation exchange membrane and the CuTAPc-CS anion exchange membrane were increased. In comparison with the mSA/mCS BPM modified by Fe3+ or ferrocene, the membrane impedance and the IR drop of the CuTsPc-SA/mCS BPM or the mSA/CuTAPc-CS BPM decreased. The CuTsPc-SA/mCS BPM had the lowest cell voltage, which was only 5.6 V at a higher current density of 120 mA cm−2. When the concentration of CuTsPc or CuTAPc was 5.0 wt%, both of the CuTsPc-SA/mCS BPM and the mSA/CuTAPc-CS BPM were stable in the acid solution ([H+] < 8 mol L−1).