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. ... mehrAnalysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.