Synthesis and characterization of TiO₂ rutile@anatase core-shell photocatalyst

Full text: Among the metal oxides applied to the photocatalysis, TiO₂ has been extensively studied due to its high photoactivity, relatively low cost, and chemical stability. Anatase and rutile are the main phases of TiO₂ and the mixture between them exhibit better photocatalytic performance when compared to TiO₂ in single phase [1].Thus, the objective of this work was to synthesize TiO₂ core-shell nanostructured (TCS1) employing solvothermal method in ethanol with autoclave maintained at 140 °C for 6 h. Commercial TiO₂ rutile and titanium (IV) isopropoxide were used as precursors of core and shell, respectively. In order to compare, rutile (TCS2) and titanium (IV) isopropoxide (TCS3) were submitted separately under the same conditions syntheses, and with the obtained products a physical mixture was also made between them (TCS4). Rietveld refinements in the X-rays patterns show that the TCS1 sample is composed by rutile and anatase TiO₂ phases in mass concentrations of 88.3% and 11.7%, respectively, different from the concentrations of the other samples. Furthermore, X-ray diffraction of the TCS3 sample revealed a low degree of crystallinity. Materials photocatalytic activity was evaluated by photodegradation of methylene blue (MB) dye under UVC light irradiation and, according to results, TCS1 sample showed 69% discoloration of the MB dye solution after 60 min and 84% after 90 min, significantly higher values when compared to degradations after 60 min using only UVC light (18%) and samples TCS2 (24%) and TCS4 (54%). The higher photocatalytic activity of the TiO₂ rutile@anatase core-shell structure was attributed to the synergistic effect of the rutile-anatase phases, providing a lower rate of recombination of the photogenerated electron-hole pair, increase the quantum efficiency of the material. Reference: [1] A. Leelavathi et. al. RSC Adv. v. 3, p. 20970-20977 (2013). (author)