Electro-photocatalytic degradation of acid orange II using a novel TiO2/ACF photoanode

A novel photoanode was prepared by immobilizing TiO2 film onto activated carbon fibers (TiO2/ACF) using liquid phase deposition (LPD) to study the electro-photocatalytic (EPC) degradation of organic compounds exemplified by an azo-dye, namely, Acid Orange II (AOII). Results demonstrated that by applying a 0.5 V bias (vs. SCE) across the TiO2/ACF electrode, the AOII degradation rate was increased significantly compared to that of photocatalytic (PC) oxidation. The application of an electric field promotes the separation of photogenerated electrons and holes as confirmed by electrochemical impedance spectroscopy (EIS) measurements. The structural and surface morphology of the TiO2/ACF electrode was characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). SEM images showed that TiO2 was deposited on almost every carbon fiber with an average thickness of about 200 nm with the inner space between neighboring fibers being maintained unfilled. The morphological features of the photo-anode facilitated the passage of solution as well as UV light through the felt-form electrode and created a three-dimensional environment favorable to EPC oxidation. Both the large outer surface area of the 3D electrode and the good organic adsorption capacity of the ACF support promoted high contact efficiency between AOII and TiO2 surface. Anatase was the major crystalline TiO2 deposited. UV–vis spectrophotometry, TOC (total organic carbon) analysis, and HPLC technique were used to monitor the concentration change of AOII and intermediates as to gain insight into the EPC degradation of AOII using the TiO2/ACF electrode.