TiO2 nanotube array modified with polypyrrole for efficient photoelectrocatalytic decolorization of methylene blue

In this work, polypyrrole (PPy) was in situ polymerized on the surface of TiO2 nanotube array (TiO2 NTA, with average pore diameter of 110 nm and length of 490-750 nm) using cyclic voltammetry method to develop the nanocomposite photoelectrode of PPy@TiO2 NTA. The morphology and the physicochemical properties of the photoelectrode were characterized by SEM, XRD, FTIR, Raman Spectra, and XPS. It was found that the PPy modification enlarged the light adsorption range of the photoelectrode, as well as increased the photocurrent density under UV light irradiation. Furthermore, the performance of PPy@TiO2 NTA photoelectrode was investigated for the decolorization of methylene blue (MB) by means of photocatalytic (PC), electrocatalytic (EC) and photoelectrocatalytic (PEC) degradation. The decolorization rate of MB using the PPy@TiO2 NTA increased by 24.94% and 10.85% under PC and EC conditions, respectively, in comparison with the decolorization rate obtained using pristine TiO2 NTA. The improved decolorization rate of MB was mainly attributed to the separation efficiency of electron-hole pairs originated from TiO2, and the enhanced utilization of visible-light due to the presence of PPy. Furthermore, the decolorization rate of MB under the PEC condition was also significantly improved, compared with the sum of the decolorization rate of PC and EC systems, indicating the synergistic effect of MB oxidation in the photoelectrocatalysis. (C) 2019 Elsevier B.V. All rights reserved.