Origin of giant permittivity in Ta, Al co-doped TiO2: Surface layer and internal barrier capacitance layer effects

TiO2 prepared by a green aqueous sol–gel peptization process is co-doped with nitrogen and zirconium to improve and extend its photoactivity to the visible region. Two nitrogen precursors are used: urea and triethylamine; zirconium (IV) tert-butoxide is added as a source of zirconia. The N/Ti molar ratio is fixed regardless of the chosen nitrogen precursor while the quantity of zirconia is set to 0.7, 1.4, 2, or 2.8 mol%. The performance and physico-chemical properties of these materials are compared with the commercial Evonik P25 photocatalyst. For all doped and co-doped samples, TiO2 nanoparticles of 4 to 8 nm of size are formed of anatase-brookite phases, with a specific surface area between 125 and 280 m2 g−1 vs. 50 m2 g−1 for the commercial P25 photocatalyst. X-ray photoelectron (XPS) measurements show that nitrogen is incorporated into the TiO2 materials through Ti-O-N bonds allowing light absorption in the visible region. The XPS spectra of the Zr-(co)doped powders show the presence of TiO2-ZrO2 mixed oxide materials. Under visible light, the best co-doped sample gives a degradation of p-nitrophenol (PNP) equal to 70% instead of 25% with pure TiO2 and 10% with P25 under the same conditions. Similarly, the photocatalytic activity improved under UV/visible reaching 95% with the best sample compared to 50% with pure TiO2. This study suggests that N/Zr co-doped TiO2 nanoparticles can be produced in a safe and energy-efficient way while being markedly more active than state-of-the-art photocatalytic materials under visible light.

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Electronic, Structural, and Optical Structure of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells—A First Principles Study

Materials ◽

10.3390/ma14143918 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3918

Author(s):

Ratshilumela S. Dima ◽

Lutendo Phuthu ◽

Nnditshedzeni E. Maluta ◽

Joseph K. Kirui ◽

Rapela R. Maphanga

Keyword(s):

Solar Cells ◽

Band Gap ◽

Dye Sensitized Solar Cells ◽

Visible Region ◽

Electromagnetic Spectrum ◽

Doped Tio2 ◽

Dye Sensitized ◽

Sensitized Solar Cells ◽

Co Doped ◽

Optical Structure

Titanium dioxide (TiO2) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO2 polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO2 brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO2 brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO2 brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO2 brookite (210) surfaces.

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Photo-activity and low resistivity in N/Nb Co-doped TiO2 thin films by combinatorial AACVD

Journal of Materials Chemistry A ◽

10.1039/c5ta07922e ◽

2016 ◽

Vol 4 (2) ◽

pp. 407-415 ◽

Cited By ~ 14

Author(s):

Nicholas P. Chadwick ◽

Emily N. K. Glover ◽

Sanjayan Sathasivam ◽

Sulaiman N. Basahel ◽

Shaeel A. Althabaiti ◽

...

Keyword(s):

Thin Films ◽

Functional Properties ◽

Tio2 Thin Films ◽

Doped Tio2 ◽

Low Resistivity ◽

Co Doping ◽

Co Doped

Combinatorial AACVD has achieved the production of various niobium/nitrogen co-doped TiO2 materials in a single film. The co-doping concentrations have been correlated with functional properties.

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