The Role of Cerium Valence in the Conversion Temperature of H₂Ti₃O₇ Nanoribbons to TiO₂-B and Anatase Nanoribbons, and Further to Rutile

CeO₂-TiO₂ is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO₂ nanostructures decorated with CeO₂ nanoparticles at the surface. As the precursor, we used H₂Ti₃O₇ 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 Ce⁴⁺-modified nanoribbons revealed a thin continuous layer at the surface of the H₂Ti₃O₇ nanoribbons, while Ce³⁺ 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 CeO₂ nanoparticles on the surface of the TiO₂ nanoribbons, whose size increased with the calcination temperature. The use of Ce⁴⁺ raised the temperature required for converting H₂Ti₃O₇ to TiO₂-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce³⁺ 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.