Herein, we report that organic dyes with poor adsorption on photocatalysts (e.g., OG (orange G) on TiO 2 ) can only be significantly degraded via the indirect oxidation process by the electrochemical photocatalytic (EPC) or photo-electro-Fenton (PEF) mechanisms because of their enhanced electron-hole separation for generating H 2 O 2 . The TiO 2 /Ti photo-anodes were prepared by cathodic deposition from a bath containing TiCl 3 , HCl, H 2 O 2 , and NaNO 3 under a two-electrode mode for EPC dye degradation. Effects of the deposition cell voltage, deposition time, and annealing temperature on the photocatalytic activity of TiO 2 films, evaluated by the photocurrent density, are systematically investigated. The surface morphologies and crystalline structure of various TiO 2 films were studied using scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. The EPC characteristics of TiO 2 /Ti photo-anodes combined with a graphite cathode toward the OG degradation have also been evaluated. The maximal photocatalytic activity is obtained for the TiO 2 /Ti photo-anode deposited at a cell voltage of 2.6 V for 20 min and annealed at 700 • C in air for 1 hr, which exhibits a photocurrent density of 22.86 μA mg −1 . The order of degradation modes with respect to decreasing the degradation efficiency of OG is: PEF > EPC > PC (photocatalytic) > EC (electrocatalytic) oxidation.In recent years, TiO 2 in various forms (e.g., anatase, rutile, and brookite phases) has been widely recognized as the most popular photocatalyst for photo-electrodes, due to its high photocatalytic activity and chemical stability under ultraviolet light excitation for water and air purifications, 1-3 photocatalysts, 4 gas sensors, 5 electrochromic devices, 6 etc. When TiO 2 was employed as a photo-anode for organic chemicals degradation, its electro-photocatalytic activity, significantly affected by the electron transport rate meanwhile characteristics of recalcitrant organic pollutants mainly depend on the microstructures (e.g., crystalline structure, crystal size, film thickness, etc.) of TiO 2 , substrate, applied potential bias, solution pH, and electrolyte conductivity. 7,8 Fortunately, the microstructure of TiO 2 films can be controlled by varying the preparation methods and parameters.Titanium dioxide films can be prepared by sol-gel method, 9,10 direct oxidation of metallic titanium, 11 chemical vapor deposition (CVD), 12 hydrothermal synthesis, 13 electrospinning, 14 magnetron sputtering, 15,16 anodizing, 17 and electrodeposition. 18-20 Among the above mentioned methods, anodizing and electrodeposition are the most common methods for fabricating TiO 2 photo-anodes for the photo-electrochemical processes (e.g., photo-electro-Fenton (PEF) and photo-electro-catalysis (PEC) reactions). Moreover, electrodeposition is preferred because this process generally provides the advantages such as uniform deposition on substrates of complex shapes and cost effective meanwhile the thickness can also be controlled by varying the charge density....
