Preparation And Photocatalytic Activities Of Zirconium-Iodine Codoped Titanium Dioxide And Silver Iodate Modified Silver Iodide-Titanium Dioxide

In this study, zirconium and iodine co-doped titanium dioxide (Zr-I-TiO2) and semiconducting silver iodate (AgIO3) modified AgI/TiO2(AIT) catalyst were synthesized and the activities of the catalysts in the photocatalysis of methyl orange (MO) and p-chlorophenol (PCP) were investigated, respectively. The structure and properties of the resultant catalyst powders were characterized by X-ray diffraction (XRD), the Brunauer-Emmett-Teller method (BET), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis absorption spectroscopy (UV-vis).Zr-I-TiO2catalyst was prepared by the hydrolysis of tetrabutyl titanate, premixed with zirconium nitrate in an iodic acid aqueous solution, followed by calcination in air. As the Zr/Ti ratio was increased from0%to10%, the content of anatase was increased from81%to100%; as calcinations temperatures were increased from400to600℃, the content of anatase reduced from89%to59%, while the content of rutile increased. The photocatalytic activities of catalysts were evaluated by the decolorization of methyl orange under visible light irradiation. The photocatalytic activity of Zr-I-TiO2calcined at400℃was found to be significantly higher than that calcined at500or600℃. Based on the physico-chemical characterization, we concluded that the role of zirconium on the I-TiO2surface is to increase the number of reactive sites by generating a small crystal size and large surface area. The inhibition of electron-hole pair recombination, by trapping photo-generated electrons with Zr4+, did not contribute markedly to the improved photocatalytic activity of Zr-I-TiO2.AgIO3was used to modify the visible-light response of an AgI/TiO2(AIT) catalyst by a facile method. Based on the XRD and XPS results, the uncalcined AIT (AITun) and AIT calcined at200℃(AIT200) consisted of AgIO3, AgI and TiO2semiconductors, while that calcined at450℃(AIT450) was composed of AgI and TiO2. The activity in p-chlorophenol (PCP) degradation under visible light irradiation using either AITun or AIT200was much higher than that with AIT450, which was mainly attributed to the fact that the presence of AgIO3provided a new matching band potential. AIT200exhibited better photocatalytic properties than AITun due to its higher crystallinity after calcination. Moreover, the high catalytic activity of AIT200was maintained after five successive cyclic experiments under visible irradiation. Considering the effect of radical scavengers and N2purging on the photocatalysis process, we deduced that the probable pathway of PCP degradation was mainly a surface charge process, caused by valence band holes.