Combustion synthesized TiO2 for enhanced photocatalytic activity under the direct sunlight-optimization of titanylnitrate synthesis

Vincent Laporte
Pergamon-Elsevier Science Ltd, 2012
Article

Optimized synthesis of Ti-precursor 'titanylnitrate' for one step combustion synthesis of N- and C-doped TiO2 catalysts were reported and characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffused reflectance UV-vis spectroscopy, N-2 adsorption and X-ray photoelectron spectroscopy (XPS). XRD confirmed the formation of TiO2 anatase and nano-crystallite size which was further confirmed by TEM. UV-DRS confirmed the decrease in the band gap to less than 3.0 eV, which was assigned due to the presence of C and N in the framework of TiO2 as confirmed by Xray photoelectron spectroscopy. Degradation of methylene blue in aqueous solution under the direct sunlight was carried out and typical results indicated the better performance of the synthesized catalysts than Degussa P-25. (C) 2012 Elsevier Ltd. All rights reserved.

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Vincent Laporte
Pergamon-Elsevier Science Ltd, 2012
Article

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https://infoscience.epfl.ch/record/184364?ln=fr

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Facile synthesis of efficient visible active C-doped TiO2 nanomaterials with high surface area for the simultaneous removal of phenol and Cr(VI)

Nicolas Xanthopoulos

A single step synthesis of carbon doped TiO2 (anatase) nanomaterials have been reported by using combustion synthesis using ascorbic acid and citric acid fuels. X-ray diffraction studies indicated the formation of nanosized anatase titania, whereas, transmission electron microscopy confirmed the formation of nanosized TiO2 anatase. The carbon doping into TiO2 matrix was identified by X-ray photoelectron spectroscopy, whereas, thermogravirnetric study quantified the carbon doping. Diffuse reflettance UV-vis spectra indicated the band gap of less than 3 eV, a prerequisite for the photocatalytic activity under visible light irradiation. The N-2 adsorption studies revealed the high surface area (upto 290 m(2)/g) of the synthesized photocatalysts. Typical photocatalytic activity data indicated that the simultaneous removal of Cr(VI) and phenol is advantageous than degradation of the individual pollutants. (C) 2014 Elsevier Ltd. All rights reserved.

Pergamon-Elsevier Science Ltd2015

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Combinatorial High-Vacuum Chemical Vapor Deposition of Textured Hafnium-Doped Lithium Niobate Thin Films on Sapphire

Giacomo Benvenuti, Ali Dabirian, Scott Harada, Patrik Hoffmann, Yury Kuzminykh, Paul Muralt, Silviu Cosmin Sandu, Estelle Wagner

Combinatorial high-vacuum chemical vapor deposition (HV-CVD) was used to identify the conditions required to obtain hafnium-doped lithium niobate thin films on sapphire {001} substrates. Niobium tetraethoxydimethylaminoethoxide (Nb(OEt)(4)(dmae)), lithium tert-butoxide (Li(OBut)), and hafnium tert-butoxide (Hf(OBut)(4)) were used as precursors. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that a single phase of textured {001} Hf-doped lithium niobate film was obtained under certain precursor flux conditions. The lithium content ([Li]/([Li] + [Nb])) of the textured film was estimated using Raman spectroscopy to be about 49 mol %. The presence of hafnium inside the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements, and the hafnium content of the textured film ([Hf]/([Hf] + [Nb])) was estimated to be about 3 mol %. XPS data confirmed that Hf and Nb, respectively, are in the +4 and +5 oxidation states inside the film. The film consists of nearly parallel {001} hafnium-doped lithium niobate columns with different in-plane orientations.

2011

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Introduction of oxygen vacancies and fluorine into TiO2 nanoparticles by co-milling with PTFE

Benjamin Bauer, Vincent Laporte

Solid-state processes of introducing oxygen vacancies and transference of fluorine to n-TiO2 nanoparticles by co-milling with poly(tetrafluoroethylene) (PTFE) powder were examined by diffuse reflectance spectroscopy (DRS) of UV, visual, near- and mid-IR regions, thermal analyses (TG-DTA), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The broad absorption peak at around 8800 cm(-1) (1140 nm) was attributed to the change in the electronic states, viz, electrons trapped at the oxygen vacancies (Vo) and d-d transitions of titanium ions. Incorporation of fluorine into n-TiO2 was concentrated at the near surface region and amounted to ca. 40 at% of the total fluorine in PTFE, after co-milling for 3 h, as confirmed by the F1s XPS spectrum. The overall atomic ratio, F/Ti, determined by EDXS was 0.294. By combining these analytical results, a mechanism of the present solid state processes at the boundary between PTFE and n-TiO2 was proposed. The entire process is triggered by the partial oxidative decomposition of PTFE. This is accompanied by the abstraction of oxygen atoms from the n-TiO2 lattices. Loss of the oxygen atoms results in the formation of the diverse states of locally distorted coordination units of titania, i.e. TiO(6-n)Vo(n), located at the near surface region. This leads subsequent partial ligand exchange between F and O, to incorporate fluorine preferentially to the near surface region of n-TiO2 particles, where local non-crystalline states predominate. (C) 2012 Elsevier Inc. All rights reserved.

2012

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