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.

Balasubramanian Viswanathan

Ram Prasad Viswanath

Absorption spectroscopy

CATALYSTS

Characterization

Doping (additives)

Electronic structure

nitrogen

Synthesis (chemical)

Titanium dioxide

Band gap

OPTICAL ABSORPTION SPECTROSCOPY

precursor

Valence band

Nanostructured materials

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

Chemistry of Materials

Layered perovskite type Sr3Ti2O7 catalysts, doped with N, S and Fe have been prepared by modified polymer complex method, characterized and evaluated for photo reduction of CO2 in aqueous alkaline medium using UV-visible radiation. EDXA and XRD data reveal the incorporation of the dopants into the titanate matrix. The presence of N in substitutional and interstitial locations, S as S6+ and Fe as Fe3+ species are indicated by XPS analysis. DRS and photo luminescence studies show that the dopants form additional energy levels within the band gap, promoting visible light absorption and retarding recombination of the charge carriers. Morphological changes and smaller crystallites also minimize recombination. Layered structure of Sr3Ti2O7 facilitates easy transport of charge carriers and separation of oxidation/reduction reaction centres. Structural, morphological and photo physical characteristics of doped catalysts improve the activity significantly. Sr3Ti2O7 co-doped with N, S and Fe together, displays maximum apparent quantum yield for CO2 reduction products. This journal is © The Royal Society of Chemistry.

Fulltext

RSC Advances

Visible light driven reduction of carbon dioxide with water on modified Sr3Ti2O7 catalysts

Photo catalytic reduction of carbon dioxide by water or artificial photosynthesis to yield hydrocarbons (methane and methanol, etc., termed solar fuels) is being studied extensively, with the twin objectives of developing an effective means of limiting atmospheric CO2 levels and evolving a sustainable alternative route for production of fuels and chemicals. This short review covers the origin and thermodynamic and kinetic features of the process, the basic photocatalytic principles involved, the rationale behind the choice of different catalysts and their performance, the effect of process conditions, the effect of the structural and photophysical properties of the different catalysts on their performance, mechanistic pathways, surface transformations, challenges involved in the practical application of the process, and future directions for research. © 2012 Springer Science+Business Media B.V.

Research on Chemical Intermediates

Application of photo catalysis for mitigation of carbon dioxide

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.

International Journal of Photoenergy

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

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

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.

Applied Catalysis B: Environmental

Characterization and photocatalytic activity of N-doped TiO2 prepared by thermal decomposition of Ti-melamine complex

Synthesis, characterization, electronic structure, and photocatalytic activity of nitrogen-doped TiO2 nanocatalyst

Journal	Chemistry of Materials
ISSN	08974756
Open Access	No