Titanium Ions Dispersed into the ZrO₂ Matrix: Spectroscopic Properties and Photoinduced Electron Transfer

Abstract

In the present work, different ZrO2−TiO2 mixed oxides, which are usually employed in photocatalytic processes and as catalytic support in heterogeneous catalysis, have been prepared via sol−gel synthesis or by wet impregnation. In the former case, as indicated by X-ray diffraction and Raman spectroscopy, solid solutions based on Ti ions diluted in the ZrO2 matrix are formed in the range of Ti molar fraction from 0.01 to 0.15. These solids have interesting optical properties as the typical band gap transition of ZrO2 undergoes a red shift proportional to the Ti loading which reach the remarkable value of 1.3 eV for the highest Ti concentration. Annealing under vacuum at various temperatures causes oxygen depletion with consequent reduction of the solid which shows up mainly in terms of formation of Ti3+ reduced centers which are characterized by a typical broad EPR signal similar to that observed in reduced TiO2 (anatase). The ability of the mixed oxides in stabilizing surface superoxide anions (O2 •−) has also been investigated by EPR to obtain information both on the photoinduced charge separation process in the solids and on the state of thermally reduced systems. In the latter case the obtained evidence have some value to understand controversial problems concerning the TiO2 reduced matrix.

Synthesis, Characterization, and Photocatalytic Tests of N-Doped Zinc Oxide: A New Interesting Photocatalyst

“…These values are about 70 and 40 nm for ZnO MW and N-ZnO MW nanostructures and 136 and 107 nm for ZnO St and N-ZnO St samples, respectively. Regardless of the synthetic method employed, the insertion of dopant caused a decrease in the crystallites size; this phenomenon was already observed and reported in the literature [39,40].…”

Fluorine- and Niobium-Doped TiO2: Chemical and Spectroscopic Properties of Polycrystalline n-Type-Doped Anatase

“…where Zr 4+ substitutes Ti 4+ cations (isovalent substitution 65 ) and aluminium doped TiO 2 (Al-TiO 2 ).…”

Ce Doping Boosts the Thermo‐ and Photocatalytic Oxidation of CO at Low Temperature in TiZrO4 Solid Solutions

“…[ 17,29,30 ] The second one, weaker and partially buried in the previous signal is the evidence of superoxide species adsorbed on the tetravalent ions of the zirconium titanate lattice (O 2 •− Ti 4+ /Zr 4+ ). [ 31,32 ] This last species is characterized by a orthorhombic symmetry of the g tensor ( g xx < g y y << g zz ) and in the present case only the lower component ( g xx  g = 2.003) can be clearly observed.…”

“…•− Ti 4+ /Zr 4+ ). [31,32] This last species is characterized by a orthorhombic symmetry of the g tensor (g xx < g yy << g zz ) and in the present case only the lower component (g xx  g = 2.003) can be clearly observed.…”