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

In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) coating on graphite sheet substrate electrode was prepared through electrochemical polymerisation for degradation of methylene blue (MB). The results of Raman and FTIR spectra indicated successful electropolymerisation of PEDOT. The morphologies of PEDOT coating electrodes under different precursor solution concentrations and electrochemical polymerisation time were compared using 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 a precursor solution concentration of 0.01 M and polymerisation time of 2 h exhibited the best decolourisation efficiency for MB. Further, under the conditions of an applied direct current voltage of 0.9 V and bubbling nitrogen, the decolouration efficiency of MB was 95%. The combined action of photocatalysis and electrocatalysis strengthened the photoelectrocatalytic degradation of MB and resulted in forming 12 intermediates, which were more than the seven intermediates generated during the photocatalytic or electrocatalytic process. The photoelectrocatalytic efficiencies were 87%, 89% 86%, 83% and 80%, respectively, in the five cycle experiments, which proved the certain stability of PEDOT.