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

Polona Umek; Michael Dürrschnabel; Leopoldo Molina-Luna; Srečo Škapin; Romana Cerc Korošec; Carla Bittencourt

doi:10.3390/molecules28155838

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

Molecules. 2023 Aug 3;28(15):5838. doi: 10.3390/molecules28155838.

Authors

Polona Umek¹, Michael Dürrschnabel², Leopoldo Molina-Luna³, Srečo Škapin¹, Romana Cerc Korošec⁴, Carla Bittencourt⁵

Affiliations

¹ Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia.
² Karlsruhe Institute of Technology, P.O. Box 6980, 706049 Karlsruhe, Germany.
³ Department of Materials and Earth Sciences, Technische Universität Darmstadt, Peter-Grünberg-Strasse 2, 64287 Darmstadt, Germany.
⁴ Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna Pot 113, 1000 Ljubljana, Slovenia.
⁵ Chimie des Interactions Plasma-Surface (ChIPS), Research Institute for Materials Science and Engineering, University of Mons, 7000 Mons, Belgium.

Abstract

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.

Keywords: CeO2; CeO2-TiO2; TiO2; TiO2-B; anatase; calcination; impregnation; ion exchange; mixed oxides; transformation.

Grants and funding

This research was funded by Slovenian Research and Innovation Agency, through the Research Program P1-0125. C.B. is a Research Associate of the FRS-FNRS, Belgium.