The Role of Cerium Valence in the Conversion Temperature of H 2 Ti 3 O 7 Nanoribbons to TiO 2 -B and Anatase Nanoribbons, and Further to Rutile
CeO 2 -TiO 2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO 2 nanostructures decorated with CeO 2 nanoparticles at the surface. As the precursor, we used H 2 Ti 3 O 7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF–STEM mapping of the Ce 4+ -modified nanoribbons revealed a thin continuous layer at the surface of the H 2 Ti 3 O 7 nanoribbons, while Ce 3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO 2 nanoparticles on the surface of the TiO 2 nanoribbons, whose size increased with the calcination temperature. The use of Ce 4+ raised the temperature required for converting H 2 Ti 3 O 7 to TiO 2 -B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce 3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.