Comparative study of the photocatalytic, electrocatalytic and photoelectrocatalytic behaviour of poly(3,4-ethylenedioxythiophene)

Abstract In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) coating on graphite sheet substrate electrode was prepared by electrochemically polymerizing in order to degrade methylene blue (MB). The results of integrating Raman spectroscopy and FTIR spectroscopy indicated successful electropolymerization of PEDOT. The morphologies of PEDOT coating electrodes under different precursor solution concentrations and electrochemical polymerization time were compared via field emission scanning electron microscopy (FESEM). The UV–visible diffuse reflectance spectrum (UV–vis DRS), cyclic voltammetry (CV), transient photocurrent response and electrochemical impedance spectroscopy (EIS) were adopted to evaluate photoelectrochemical properties. The PEDOT electrode with precursor solution concentration of 0.01 M and polymerization time of 2 h exhibited the best decolorization efficiency for MB. Further, under the conditions of applied direct current voltage of 0.9 V and bubbling nitrogen, the decoloration efficiency of MB was 95%. The combined action of photocatalysis and electrocatalysis strengthened the photoelectrocatalytic degradation of MB and resulted in forming of 12 intermediates, which were more than the 7 intermediates generated during the photocatalytic or electrocatalytic process. The photoelectrocatalytic efficiency was 87%, 89% 86%, 83% and 80%, respectively, in the five cycle experiments, which proved certain stability of PEDOT.