The Nanocrystalline SnO₂–TiO₂ System—Part I: Structural Features

Abstract

The phases present and their crystal structure and microstructure in the nanocrystalline SnO 2 -TiO 2 system were studied in the compositional range Sn 1 -x Ti x O 2 (0.0 ≤ x ≤ 0.9). There is an apparent increase in the solubility limits in the solid solution compared to bulk crystalline SnO 2 -TiO 2 . No two phase region was observed with increasing TiO 2 content. Electron energy loss spectroscopy, infrared spectroscopy (FTIR), and X-ray diffraction (XRD) of the nanopowders showed that the apparent increase in solubility is related to the systematic Ti 4+ segregation on the particle surface (surface excess) at the SnO 2rich side, avoiding the nucleation of a second phase even at high Ti 4+ contents. Is this finding in accord with Raman spectra, which suggest localized Ti-rich sites in the absence of a second crystalline phase. Ti 4+ surface excess is also lead to a modification of the surface hydroxyls and a decrease in the crystallite size of the nanoparticles (with a concomitant increase in surface area), with expected implications to catalytic and sensorial properties of these nanoparticles.G. Rohrer-contributing editor Manuscript No. 36322.

Ternary Sn‐Ti‐O Electrocatalyst Boosts the Stability and Energy Efficiency of CO2 Reduction

“…In this case, formation of TiO 2 ‐rich regions caused shifting and transition of SnO 2 peaks towards TiO 2 anatase. At 100 mol % TiO 2 composition, the phase diagram predicts a rutile phase . Interestingly, our 3DOM structure appeared as anatase, which has higher catalytic activity than the rutile phase .…”

“…Considering the differences between nanomaterial and bulk material solidification, the deviation from the phase diagram is understandable. The 3DOM nanostructure presents itself with a larger solubility range and formation of anatase rather than rutile because of: 1) the extra energy applied during the sonication procedure, 2) possibility of liquid and solid phase coexistence in small dimensions, and 3) more Ti accommodation because of atomic segregation towards the surface, which avoids nucleation of another phase . The special Sn‐Ti ratio (Sn 0.3 Ti 0.7 O 2 ) is most likely the crucial turning point for spinodal decomposition for the nanobinary materials (see Figure S6c).…”

The Nanocrystalline SnO2–TiO2 System‒Part II: Surface Energies and Thermodynamic Stability

“…As discussed in Ref. , one can explain the abrupt decrease in the surface energy by addressing Ti 4+ segregation as a Gibbs surface excess. As such, an enrichment of the surface would decrease the surface energy according to Eq.…”

“…Sn 1− x Ti x O 2 powders with 0.00 ≤ x ≤ 0.90 and step of x = 0.10 were synthesized by a polymeric precursor method derived from Pechini's patent, and all samples were calcined at the same temperature for similar times. Details on the synthesis methods and characterization of the powders can be found elsewhere . Pure TiO 2 synthesized by polymeric precursor method was not studied in this work due to the fact that sample crystallizes in the anatase structure, alternatively, co‐precipitation technique was used to produce pure rutile TiO 2 .…”

Segregação superficial de MgO em nanopartículas de TiO2

“…Diversos trabalhos buscam melhorar a atividade fotocatalítica do TiO 2 por meio da introdução de aditivos, tanto de cátions como de ânions [3][4][5]. Contudo, poucos trabalhos têm sido realizados para entender os fenômenos de segregação na superfície de partículas de TiO 2 e como esse processo afeta a sua atividade catalítica [6][7][8].…”