INFLUENCE OF HETEROATOM DOPING OF TiO2 NANOPARTICLE ON THE RED SHIFT AND THE RELATED CATALYTIC ACTIVITY
01 Apr 2007-International Journal of Nanoscience (World Scientific Publishing Company)-Vol. 06, Iss: 02, pp 137-141
TL;DR: In this paper, N-doped anatase TiO2 has been prepared by thermal decomposition of Ti containing metal complexes and the light absorption onset has been shifted to the visible region by ~ 100 nm.
Abstract: N-doped anatase TiO2 has been prepared by thermal decomposition of Ti containing metal complexes. The light absorption onset has been shifted to the visible region by ~ 100 nm when compared to pure TiO2. The N environment of N-doped TiO2 has been studied by XPS and the results confirm the presence of N–Ti–O in the N-doped samples. Also, there is a shift in the binding energy values of Ti 2p3/2, and the additional peak for O 1s in N-doped TiO2 confirms the increase in the covalent nature of TiO2 during the N-doping. The photocatalytic activity of N-doped TiO2 has been studied both in the UV and visible regions and N-doped TiO2 shows higher activity than the Degussa TiO2 in the visible region.
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TL;DR: In this paper, the phase transition of TiO 2 from anatase to rutile crystalline phase, starting at calcination temperature ≥600 ˚C, was revealed through X-ray photoelectron spectroscopy.
Abstract: Nitrogen doped spherical TiO 2 has been prepared by thermal decomposition of Ti–melamine complex in air atmosphere. A clear shift in the onset light absorption from UV region ( 520 nm) has been observed for the N-doped samples. It has been deduced from the optical absorption spectra that the higher calcination temperature results in the decrease in the amount of N-doping. The XRD results revealed the phase transition of TiO 2 from anatase to rutile crystalline phase, starting at calcination temperature ≥600 °C. The electron microscopic images reveal the formation of spherical and flakes of TiO 2 nanocrystals (25 nm). The chemical nature of N in the N-TiO 2 has been evolved through X-ray photoelectron spectroscopy. The presence of different types of N species have been observed corresponding to different oxidation states and the presence of Ti–N and O–Ti–N have been confirmed from the observed binding energy values. Photocatalytic decomposition of methylene blue has been carried out both in the visible region and UV + visible region. In the visible region, N-TiO 2 showed higher activity compared to the undoped commercial TiO 2 (Degussa P25).
125 citations
TL;DR: In this paper , the authors describe the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO2.
Abstract: This paper describes the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO2. The synthesis is performed using titanium oxysulfate as a low-cost inorganic precursor and ammonia as a precipitating agent, as well as a source of nitrogen. Mixing the reagents under a control of pH leads to an amorphous titanium oxide hydrate, which can be further successfully converted to nanocrystalline anatase TiO2 through calcination in air at an increased temperature. The as-prepared N-doped TiO2 provides the complete oxidation of volatile organic compounds both under UV and visible light, and the action spectrum of N-doped TiO2 correlates to its absorption spectrum. The key role of paramagnetic nitrogen species in the absorption of visible light and in the visible-light-activity of N-doped TiO2 is shown using the EPR technique. Surface modification of N-doped TiO2 with copper species prevents its intense deactivation under highly powerful radiation and results in a nanocomposite photocatalyst with enhanced activity and stability. The photocatalysts prepared under different conditions are discussed regarding the effects of their characteristics on photocatalytic activity under UV and visible light.
4 citations
TL;DR: In this paper, the photocatalytic activity of Tungsten trioxide and titania composites was evaluated by the photodegradation of methylene blue (MB) under UV and visible light irradiation.
Abstract: Tungsten trioxide and titania composites (WTs) were prepared by acid precipitation following sol-gel method. The photocatalytic activity of WT was evaluated by the photodegradation of methylene blue (MB) under UV and visible light irradiation. Effects of dispersion state in the WTs with different composition on the photocatalytic activity were investigated. Highly dispersed agglomerates consisting of monoclinic WO3 and anatase TiO2 nanoparticles were formed. As a result, the WO3/TiO2 photocatalyst with the atomic fraction, W/(W+Ti), of 0.5 showed the highest photocatalytic activity to the MB degradation under UV and visible light irradiation.
2 citations
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...photocatalysts by doping of nitrogen, carbon or sulphur to TiO2 [4] and by coupling of TiO2 with active semiconductors to the visible light [5]....
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References
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TL;DR: Film and powders of TiO2-x Nx have revealed an improvement over titanium dioxide (TiO2) under visible light in optical absorption and photocatalytic activity such as photodegradations of methylene blue and gaseous acetaldehyde and hydrophilicity of the film surface.
Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.
11,402 citations
TL;DR: In this paper, x-ray photoelectron spectroscopy was used to investigate the oxidation mechanisms at 350°C during this initiation time period, and the oxide thickness increases slowly with oxidation time and the film appears to change from an amorphous TiO2 layer to a crystalline TiO 2 layer.
Abstract: We report a study of the oxidation of TiN. In previous work, the oxidation kinetics for 350–450 °C were reported and an initiation time prior to fast oxidation was identified. In this study, x‐ray photoelectron spectroscopy was used to investigate the oxidation mechanisms at 350 °C during this initiation time period. The oxide thickness increases slowly with oxidation time and the film appears to change from an amorphous TiO2 layer to a crystalline TiO2 layer. Spectral features which are intermediate between TiO2 and TiN are reported and a model involving grain boundary oxidation is proposed. One of the thicker oxides studied was annealed in vacuum to 700 °C. Following oxidation, some of the capping oxide and much of the intermediate material is no longer in the analysis volume and we suggest that the oxygen and nitrogen is being dissolved into the bulk in much the same way that nonevaporable getters are activated before use.
1,078 citations
TL;DR: In this article, rare earth (RE=La3+, Ce3+, Er3+, Pr3+, Gd3+-doped, Nd3+, Sm3+, Nd4+, Sm5+ and Sm6+ were used as precursors for the synthesis of RE/TiO2 photocatalysts, which were characterized by XRD, IR, UV-vis diffuse reflection and transient absorption spectra.
Abstract: RE/TiO2 photocatalysts were prepared by the sol–gel method using rare earth (RE=La3+, Ce3+, Er3+, Pr3+, Gd3+, Nd3+, Sm3+) metal salts and tetra-n-butyl titanate as precursors, and were characterized by XRD, IR, UV–vis diffuse reflection, and transient absorption spectra. Their photocatalytic activities were evaluated using nitrite as a decomposition objective. As a result, suitable content of doping rare earth in TiO2 can efficiently extend the light absorption properties to the visible region. At the same time, it is beneficial to NO2− adsorption over the catalysts due to rare earth doping. RE/TiO2 samples can enhance the photocatalytic activity to some extent as compared with naked TiO2. The increase in photoactivity is probably due to the higher adsorption, red shifts to a longer wavelength, and the increase in the interfacial electron transfer rate. Nitrite is almost completely degraded over RE/TiO2 catalysts after longer irradiation, which is different from Degussa P-25 with a plateau of activity after ca. 20 min irradiation. Gd3+-doped TiO2 showed the highest reaction activity among all concerned RE-doped samples because of its specific characteristics. The amount of RE doping was an important factor affecting photocatalytic activity; the optimum amount of RE doping is ca. 0.5 wt%, at which each RE/TiO2 sample shows the most reactivity. The photocatalytic degradation reaction of nitrite over Gd3+-doped samples and P-25 follows apparent first order kinetics, which is different from that of Sm3+, Ce3+, Er3+, Pr3+, La3+, and Nd3+-doped TiO2 catalysts, which obey zero-order kinetics, indicating that these processes were dominated by electron–hole recombination.
1,067 citations
TL;DR: In this paper, S-doped TiO2 particles were used for degradation of methylene blue in aqueous solution under irradiation at wavelengths longer than 440 nm, and the oxidation state of the S atoms incorporated into the particles was determined to be S6+ from the XPS spectra.
Abstract: In order to effectively utilize visible light in photocatalytic reactions, we have developed S-doped TiO2 particles. They show strong absorption for visible light and high activities for degradation of methylene blue in aqueous solution under irradiation at wavelengths longer than 440 nm. The oxidation state of the S atoms incorporated into the TiO2 particles is determined to be S6+ from the XPS spectra.
865 citations
TL;DR: The spectral sensitization of TiO2 in this case was concluded to be due to NOx impurity which was formed from NF4OH used in the preparation of titanium hydroxide as mentioned in this paper.
Abstract: When powdered TiO2 was prepared from a commencal titanium hydroxide by calcination, its color turned to pale yellow at around 400°C and this yellow-colored TiO2 showed higher photocatalytic activity for oxygen isotope equilibration and the oxidation of carbon monoxide and ethane than standard TiO2 in the visible light region (434 nm). The spectral sensitization of TiO2 in this case was concluded to be due to NOx impurity which was formed from NF4OH used in the preparation of titanium hydroxide.
669 citations