Two Photoelectrochemical Processes for TiO_2 Electrode under UV Illumination

TiO 2 thin film electrode was prepared by a sol gel method on ITO substrates. Cyclic voltammetric behavior of the ITO/TiO 2 electrode under ultraviolet (UV) illumination was investigated in the solution of Na 2SO 4. There are two photoelectrochemical processes for TiO 2 electrode under UV illumination. One is a fast process, which results in the appearance of anodic photocurrent. The anodic photocurrent will appear and disappear with the light on and off. The other is a slow process, which will be responsible for the appearance of an oxidative peak. When the electrode is illuminated under UV light for a long time, a new oxidative peak can be observed. The peak current increases with the increase of UV illumination time. It is assumed that the new peak belongs to the oxidation of Ti 3+ , which formed and accumulated on the electrode surface during the UV illumination. A detailed mechanism is proposed on the base of these two photoelectrochemical processes. It is assumed that the change of hydrophilicity of TiO 2 thin film may be related to the slow process while the film irradiated by UV light.

Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO_2 nano-sheets in aqueous phase

Titanium dioxide （TiO2）, which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabntyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetra- chloroethene （PCE）, tdchloroethene （TCE） and 1,1,l-trichloroethane （TCA）. The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commerciai P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene （NB） as a probe of hydroxyl radical （.OH）, the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of .OH generated in UV/synthesized TiO2 system. In addition, .OH concentration was confirmed by the strong peak displayed in EPR analysis over U~/synthesized TiO2 system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 rim, side length of 50 nm and width of 33 nra and a surface 90.3 m^2/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.

Effects of UV on the Corrosion Behavior of Pure Aluminum 1060 in Simulated Nansha Marine Atmosphere

The corrosion behavior of pure aluminum 1060 subjected to a wet-dry cyclic accelerated test in simulated Nansha marine atmosphere in the dark and under UV illumination has been investigated by means of scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS),and Mott–Schottky measurements in this work.The results show that under the two conditions,the native oxide films are constantly destroyed and the thicknesses of the oxide films continuously decrease in the first 24 days of the corrosion test.In particular,UV illumination can diminish the pitting corrosion susceptibility of the native oxide films to an extent in terms of a photo-induced modifi cation of the native oxide film on the pure aluminum surfaces.Besides,UV illumination can also reduce the carrier concentration in the oxide films,thus reducing the conductivity and the corrosion rate.