Photoelectrochemical and photocatalytic properties of nanocn stalline TiO_2 electrodes

摘要

The electrochemical and photocatalytic properties of a TiO_2 film deposited on transparent electrodes were investigated. Its electrochemical behavior was typical of an n-type semiconductor electrode. Its photocatalytic activity, investigated for phenol degradation on an optical bench (area of 1 cm~2, 5 mL of solution), revealed small currents (3 μA) and poor total organic carbon (TOC) removal (5 %) when the electrode was biased at + 1.1 V in the dark for 3 h. Under polychromatic irradiation, the electrode presented 25 μA of current and 12 % of phenol degradation. A better performance was achieved for photoelectrocatalytic configuration, when the electrode was irradiated and biased with + 0.6 V. Experiments done under irradiation with a metallic vapor lamp using 9 cm~2 electrodes and 10 mL of solution revealed that heterogeneous photocatalysis configuration (HPC) resulted in 50 % of TOC removal, while 85 % was achieved by the electro-assisted process (EHPC). Both the configurations exhibited pseudo-first order kinetics for phenol degradation, but the rate constant was two times that of EHPC. The application of a potential bias to the TiO_2 porous electrode must enhance the photogenerated electron/hole separation, which minimize the charge recombination and increases its photocatalytic activity towards organic pollutant degradation.