Preparation and characterization of bipolar membranes modified using photocatalyst nano‐TiO₂ and nano‐ZnO

The nano‐ZnO and nano‐TiO 2 were added into chitosan (CS) anion layer to prepare polyvinyl alcohol (PVA) ‐ sodium alginate (SA)/ TiO 2 ‐ZnO‐CS (here, PVA:polyvinyl alcohol; SA:sodium alginate) bipolar membrane (BPM), which was characterized using scanning electron microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TG), electric universal testing machine, contact angle measurer, and so on. Experimental results showed that nano‐TiO 2 ‐ZnO exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano‐TiO 2 or nano‐ZnO. The membrane impedance and voltage drop (IR drop) of the BPM were obviously decreased under the irradiation of high‐pressure mercury lamps. At a current density of 60 mA/cm 2 , the cell voltage of PVA‐SA/TiO 2 ‐ZnO‐CS BPM‐equipped cell decreased by 1.0 V. And the cell voltages of PVA‐SA/TiO 2 ‐CS BPM‐equipped cell and PVA‐SA/ZnO‐CS BPM‐equipped cell were only reduced by 0.7 and 0.6 V, respectively. Furthermore, the hydrophilicity, thermal stability, and mechanical properties of the modified BPM were increased.