Preparation and Characterization of Bipolar Membrane Modified by Iron-Phthalocyanine with Different Amounts of Carboxyl Groups

Iron-phthalocyanines (Fe-phthalocyanines) with different amounts of carboxyl groups were added into carboxymethylcellulose (CMC) cation exchange membrane to prepare the modified CMC/CS bipolar membranes (BPMs, CS: chitosan), which were characterized using electric universal testing machine, contact angle measurer and so on. Experimental results showed that the ion exchange capacity, hydrophilicity of CMC membrane and mechanical properties of the BPM notablely got better after Fe-phthalocyanines were added. Furthermore, a high charge density area formed in the interlayer of the BPM after modification, which sped up water dissociation and lowered the membrane impedance. At the current density of 60 mA cm-2, the cell voltages of Fe2Pc2(COONa)12-CMC/CS BPM, FePc (COONa)8-CMC/CS BPM, FePc (COONa)4-CMC/CS BPM and CMC/CS BPM were 5.6V, 6.2V, 6.5V and 8.9V respectively [here, Fe2Pc2(COONa)12: planar binuclear iron (III) phthalocyanine; FePc (COONa)8:iron (III) octocarboxyphthalocyanine; FePc (COONa)4:iron (III) tetracarboxyphthalocyanine]. The cell voltage of Fe2Pc2(COONa)12-CMC/CS BPM was the smallest.