Study on photocatalytic degradation of gaseous 1,2-dichloroethane using Pd/TiO₂ and V/TiO₂ prepared by a sol-gel method

The Pd/TiO₂ and V/TiO₂ prepared by a sol-gel method calcined at 500 °C for 3 h was characterized in this study. The synthesized photocatalysts were used for the photodegradation of 1,2dichloroethane (1,2-DCE). From X-ray powder diffraction data, the crystal phase presents the mixture of anatase and rutile phases, and anatase is the dominant phase. The crystallites of photocatalysts are spherical particles with a crystallite size about 10-20 nm. UV-Visible diffuse reflectance spectra of Pd/TiO₂ and V/TiO₂ show an increase in absorbency in the visible light region with the increasing dopant concentration. The X-ray photoelectron spectroscopy results indicate that the doped vanadium ions should exist in the form of V ⁴⁺. From 1,2-DCE photocatalytic degradation, the performance of Pd/TiO₂ is worse than that of TiO₂ alone. The presence of palladium ions may increase the adsorption of byproducts adsorbed on the surface of Pd/TiO₂, therefore reducing the number of available active sites for the photocatalytic reaction. Furthermore, the performance of V/TiO ₂ is better than that of TiO₂ alone, and the optimum vanadium dopant concentration is 0.01 mol%. V⁴⁺ can act as both holes and electron traps to reduce the recombination rate of electron-hole pairs and enhance the photocatalytic activity. From surface area data, he surface areas of Pd/TiO₂ or V/TiO₂ are similar to those of TiO ₂, and the photocatalytic activity of V/TiO₂ with low levels of vanadium dopant is better than that of TiO₂ alone. From SEM images and EDS results, the deactivation phenomena occur when the byproducts are irreversibly chemisorbed to the active sites of photocatalysts. The intermediates of 1,2-DCE photocatalytic degradation include C₂H ₅CI, CH₂CI₂, and HCl.