Synergistic degradation of organic pollutants by poly (3,4-ethylenedioxythiophene) based photo-electrocatalysis

Abstract

Poly (3,4-ethylenedioxythiophene) (PEDOT) had been explored as photosensitizer and hole transport agent. However, coating PEDOT on metal electrodes had issues with poor adhesion and delamination. In this work, the composite electrode with improved photo-electrocatalytic performance was constructed by potentiostatic polymerization of PEDOT on graphite plate and subsequent loading of ZnIn2S4. Solid micro-nanowires were observed in pure ZnIn2S4 electrode, which changed to polygon hollow tubular structure when loading ZnIn2S4 on PEDOT surface. From the Hall effect results, the resistance of composite electrode was reduced and the carriers density and mobility were increased. The charge carrier mobility value was 173.15 cm−2·V−1·s−1, which was almost two and four times higher than PEDOT (85.90 cm−2·V−1·s−1) and ZnIn2S4 (42.90 cm−2·V−1·s−1), respectively. The optimum EDOT concentration and polymerization time of PEDOT were 0.01 M and 20 min, respectively. The optimum scanning cycles for cyclic voltammetry deposition of ZIS and the ratio of ZnCl2, InCl·4H2O and Na2S2O3·5H2O were 400 cycles and 2:4:8, respectively. The radical capture experiment showed that singlet oxygen (1O2) and superoxide radical (O2−) were produced by PEDOT anode, while 1O2, O2− and hydroxyl radical (OH) were produced by the composite cathode. Through these reactive species, the removal of tetracycline and methylene blue reached 91% and 99% after 180 min reaction, respectively, under external voltage of 0.9 V.