Nitrogen doped spherical TiO2 has been prepared by thermal decomposition of Ti-melamine complex in air atmosphere. A clear shift in the onset light absorption from UV region (&lt;400) to visible region (&gt;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 TiO2 from anatase to rutile crystalline phase, starting at calcination temperature ≥600 °C. The electron microscopic images reveal the formation of spherical and flakes of TiO2 nanocrystals (25 nm). The chemical nature of N in the N-TiO2 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-TiO2 showed higher activity compared to the undoped commercial TiO2 (Degussa P25). © 2007 Elsevier B.V. All rights reserved.

Balasubramanian Viswanathan

Ram Prasad Viswanath

Air atmosphere

Anion doping

RUTILE CRYSTALLINE PHASE

Visible light absorption

Absorption spectra

Doping (additives)

Light absorption

Phase Transitions

Photocatalysis

Pyrolysis

Titanium dioxide

Catalyst activity

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Applied Catalysis B: Environmental

The possibility of hydrogen production by photo-catalytic decomposition of water on titania has provided the incentive for intense research. Titania is the preferred semiconductor for this process, in spite of its large band gap (3.2eV) that restricts its utility only in the UV region. Various sensitization methodologies have been adopted to make titania to be active in the visible region. Doping of TiO2 with nitrogen is one such method. The purpose of this presentation is to examine the state and location of nitrogen introduced in TiO2 lattice and how far the shift of optical response to visible radiation can be beneficial for the observed photo-catalysis. The specific aspects that are discussed in this article are: (i) N-doped titania surface adopts a non-native configuration, though the bulk material is still in the native configuration of pure TiO2 (ii) Though the nitrogen doped materials showed optical response in the visible region, the changes/improvements in photo-catalytic activity are only marginal in most of the cases. (iii) The exact chemical nature/state of the introduced nitrogen, and its location in titania lattice, substitutional and/or interstitial, is still unclear (iv) Is there a limit to the incorporation of nitrogen in the lattice of TiO2? Copyright © 2012 B. Viswanathan and K. R. Krishanmurthy.

Fulltext

International Journal of Photoenergy

Nitrogen incorporation in TiO 2: Does it make a visible light photo-active material?

There is an urgent need for the development of inexpensive, but reliable and efficient photocatalyst which can work under solar radiation for drinking water application. Hence the treatment options to be tried out for drinking water contaminated with pesticides and their formulation products should be cost effective and affordable. In this study, we developed a cheap and efficient photocatalyst and continuous photoreactor for the removal of pesticides from drinking water under solar radiation. Continuous photodegradation experiments were carried out with synthetically prepared commercial grade methyl parathion (Folidon 50% E.C.), dichlorvos (DDVP 70% E.C.), and analytical grade lindane. Photodegradation of mixed pesticide was carried out using both Degussa P-25 TiO 2 and N-doped TiO 2 with identical mass concentrations (50μg/L) of all the three pesticides under UV, visible and solar radiation. Continuous reactor was operated for more than 24h (6h each on 4days) for mixed pesticide degradation. N-doped TiO 2 showed 100% degradation for all the three pesticide under solar radiation. Photodegradation of mixed pesticide showed methyl parathion, dichlorvos and lindane were degrading simultaneously. However, the rate of reaction was completely different from single pesticide degradation. N-doped TiO 2 showed higher photocatalytic activity under solar radiation compared to UV and visible light. GC-MS analysis of mixed pesticide degradation showed more than 16 peaks in the middle of the reaction. Among these peaks, three intermediates such as hexachloro-benzene and para-nitrophenol and dichlorovinyl-O-methyl phosphate were identified in the middle of the reaction. However, at the end of the reaction (reactor outlet) none of the intermediates were observed. © 2012 Elsevier Ltd.

Solar Energy

Elimination of pesticides and their formulation products from drinking water using thin film continuous photoreactor under solar radiation

Methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate) and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate) are the most commonly used pesticides in India. These pesticides are often found in many surface and groundwater sources and their concentration levels often exceed the drinking water permissible limits recommended by Indian and European drinking water standards. In this study, doping of nitrogen on TiO 2 was carried out with different nitrogen containing organic compounds such as triethylamine, urea, ethylamine and ammonium hydroxide. Nitrogen (N) doped TiO 2 from triethylamine precursor showed better photocatalytic activity under visible and solar radiation for the degradation of methyl parathion and dichlorvos. Studies for the photodegradation of analytical and commercial grade methyl parathion and dichlorvos were carried out with N-doped TiO 2 and Degussa P-25 TiO 2 under UV, visible and solar radiation using batch reactor. N doped TiO 2 showed higher photocatalytic activity under solar radiation compared to UV and visible light. GC-MS analysis of commercial grade methyl parathion showed intermediates such as para-nitrophenol and O,O-dimethyl phosphonic ester in the middle of the photodegradation process. Similarly, commercial grade dichlorvos showed intermediates such as 2,2-dichlorvinyl-O-methyl phosphate and O,O,O-trimethyl phosphonic ester during the reaction. However, at the end of the reaction none of the intermediates were present in the system. Photodegradation of mixed pesticides showed that methyl parathion and dichlorvos were degrading simultaneously. However, the rates of reaction were different from single pesticide degradation. © 2011 Elsevier B.V.

Chemical Engineering Journal

Photodegradation of methyl parathion and dichlorvos from drinking water with N-doped TiO 2 under solar radiation

Nitrogen doped titanium photocatalysts with different nitrogen containing organic compounds were prepared by sol-gel method in acidic media. Among different nitrogen containing organic compounds, triethylamine doped TiO2 showed better photocatalytic activity under visible light. XRD, SEM and TEM analyses showed that the crystalline size of N-doped TiO2 was in the range of 20-24 nm. XRD and Raman spectrum showed that all peaks of N-doped TiO2 correspond to anatase crystalline structure. The formation of O-Ti-N bond in N-doped TiO2 does not lead to any new Raman band. XPS study confirmed that N replaces the O in the lattice of TiO2 and is present in the form of O-Ti-N. The photocatalytic activity of doped TiO2 was measured under UV and visible light using lindane as a target pollutant. The photocatalytic activity of anatase TiO2 and N-doped TiO2 was compared with commercially available Degussa P-25 TiO2. Intermediates formed during the degradation of lindane were monitored by GC-MS analysis. © 2010 Elsevier B.V.

Photocatalytic degradation of lindane under UV and visible light using N-doped TiO2

N,S-co-doped anatase-phase TiO 2 (N,S-TiO 2) nanophotocatalysts were prepared from either benzothiazoline or aminothiol with titanium isopropoxide followed by a systematic thermal decomposition. The chemical nature of S and N in N,S-TiO 2 have been identified by XPS to be sulfate and NO-like, respectively. A significant band broadening and red-shift in the UV-visible absorption spectrum of N,S-TiO 2 suggests a band gap reduction compared to TiO 2. A maximum band-gap narrowing of 0.22±0.02 eV was observed on N,S-TiO 2. Higher energy width observed on N,S-TiO 2 is in contrast to 0.13 eV from N-doped TiO 2 indicating the sulfate-like species might play a major role in narrowing the band-gap to a higher level. It is confirmed that the oxidation of N and S to NO and SO42 occurs in the final stage of preparation of N,S-TiO 2, during calcination in air. It is predicted that the oxygen associated with sulfate and NO structural features could be crucial in bringing down the energy gap and red shift in optical absorption and the role of sulfur is to facilitate the above. Photocatalytic decomposition of methylene blue has been carried out on N,S-TiO 2 shows higher activity than the commercial TiO 2 in the visible region. However, sulfate species seems to enhance the activity of N,S-TiO 2 marginally compared to N-TiO 2, and possible suggestions are given to improve the same. Copyright © 2009 American Scientific Publishers All rights reserved.

Journal of Nanoscience and Nanotechnology

N,S-Co-doped TiO 2 nanophotocatalyst: Synthesis, electronic structure and photocatalysis

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 Is 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. © World Scientific Publishing Company.

International Journal of Nanoscience

Influence of heteroatom doping of TiO2 nanoparticle on the red shift and the related catalytic activity

Nitrogen-doped TiOz2 (N-TiO2) nanocatalyst with spherical shape and homogeneous size has been synthesized through a chemical method using TiCl3 as precursor. The light absorption onset shifts from 380 nm on pure TiO2 to the visible region at 550 nm with N-TiO2. A clear decrease in the band gap and the nitrogen 2p states on the top of the valence band on N-TiO2 (compared to TiO 2) is deduced from the optical absorption spectroscopy results. The chemical nature of N has been evolved as N-Ti-O in the anatase TiO2 lattice as identified by X-ray photoelectron spectroscopy (XPS). Photocatalytic decomposition of methylene blue has been carried out both in the UV and in the visible region and N-TiO2 shows higher activity than the Degussa P25 TiO2 photocatalyst in the visible region. © 2005 American Chemical Society.

Journal	Applied Catalysis B: Environmental
ISSN	09263373
Open Access	No