TiO2 photocatalysts doped with three transition metal ions of varying concentration were prepared by adsorption
phase synthesis. The influence of different metal ion species and contents on the morphology and crystallization of
TiO2 sintered under various temperatures was explored by transmission electron microscopy, X-ray diffractometry, UVvis
spectroscopy, and X-ray photoelectron spectroscopy. Photodegradation experiments on methyl-orange were employed
to evaluate photocatalytic activity. Results indicated that 0.05 at.% Fe3+ and Cd2+ doping introduces lattice distortions as
shallow trapping sites; moreover, doping improved the activity of adsorption phase synthesis (APS) catalysts. TiO2 crystallization
was restricted when the doping content was greater than 0.05 at.% because other metal ions destroy the TiO2
lattice structure. Restriction also increased with doping content. An optimum doping content was observed during the
preparation of TiO2 doped with Cd2+ and Fe3+. As the Fe3+ radius is close to the Ti4+ radius, the influence of Fe3+ doping
content on TiO2 crystallization and activity was more apparent than that of Cd2+ doping content. Increases in sintering
temperature resulted in fewer lattice distortions acting as shallow trapping sites and decreases in APS catalyst activities.
Keywords: Adsorption phase synthesis, methyl-orange, photodegradation, transition metal ions doping, TiO2.
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