Electrochemical photocatalytic degradation of orange G using TiO₂ films prepared by cathodic deposition

Herein, we report that organic dyes with poor adsorption on photocatalysts (e.g., OG (orange G) on TiO₂) 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 H₂O₂. The TiO₂/Ti photo-anodes were prepared by cathodic deposition from a bath containing TiCl₃, HCl, H₂O₂, and NaNO₃ 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 TiO₂ films, evaluated by the photocurrent density, are systematically investigated. The surface morphologies and crystalline structure of various TiO₂ films were studied using scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. The EPC characteristics of TiO₂/Ti photo-anodes combined with a graphite cathode toward the OG degradation have also been evaluated. The maximal photocatalytic activity is obtained for the TiO₂/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.