In situ photoelectrochemical/photocatalytic study of a dye discoloration in a microreactor system using TiO2 thin films.

In this work, we report in situ studies of UV photoelectrocatalytic discoloration of a dye (indigo carmine) by a TiO(2) thin film in a microreactor to demonstrate the driving force of the applied electrode potential and the dye flow rate toward dye discoloration kinetics. TiO(2) 65-nm-thick thin films were deposited by PVD magnetron sputtering technique on a conducting glass substrate of fluorinated tin oxide. A microreactor to measure the discoloration rate, the electrode potential, and the photocurrent in situ, was developed. The dye solutions, before and after measurements in the microreactor, were analyzed by Raman spectroscopy. The annealed TiO(2) thin films had anatase structure with preferential orientation (101). The discoloration rate of the dye increased with the applied potential to TiO(2) electrode. Further, acceleration of the photocatalytic reaction was achieved by utilizing dye flow recirculation to the microreactor. In both cases the photoelectrochemical/photocatalytic discoloration kinetics of the dye follows the Langmuir-Hinshelwood model, with first-order kinetics. The feasibility of dye discoloration on TiO(2) thin film electrodes, prepared by magnetron sputtering using a flow microreactor system, has been clearly demonstrated. The discoloration rate is enhanced by applying a positive potential (E (AP)) and/or increasing the flow rate. The fastest discoloration and shortest irradiation time (50 min) produced 80% discoloration with an external anodic potential of 0.931 V and a flow rate of 12.2 mL min(-1).