Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NO{sub x} abatement

Journal Article · Sun Nov 15 00:00:00 EST 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.08.008· OSTI ID:22573932

Pullar, R. C. ^[1]; Gualtieri, A. F. ^[2]; Otero-Irurueta, G.; Singh, M. K. ^[3]; Seabra, M. P.; Labrincha, J. A. ^[1]

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1. Department of Materials and Ceramic Engineering / CICECO−Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)
2. Dipartimento di Scienze Chimiche e Geologiche, Università degli studi di Modena e Reggio Emilia, I-41121 Modena (Italy)
3. Center for Mechanical Technology and Automation – TEMA, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal)

Titanium dioxide (TiO{sub 2}) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO{sub 2} has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO{sub 2} to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO{sub 2} lattice using our green sol–gel nanosynthesis method, used to create 10 nm TiO{sub 2} NPs. Two parallel routes were studied to produce nitrogen-modified TiO{sub 2} nanoparticles (NPs), using HNO{sub 3}+NH{sub 3} (acid-precipitated base-peptised) and NH{sub 4}OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NO{sub x}) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NO{sub x} abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO{sub 2} NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice. - Graphical abstract: Nitrogen modified TiO{sub 2} synthesised via a green aqueous sol–gel method showed to degrade nitrogen oxides (NO{sub x}) under visible white-light (indoor artificial lighting), with a photocatalytic activity double than that of the standard P25 TiO{sub 2} NPs. - Highlights: • N–TiO{sub 2} synthesised via a green aqueous sol–gel method. • Advanced X-ray methods used to detect both crystalline and amorphous contents. • Microstructure fully addressed via XRPD and whole powder pattern modelling. • Photocatalytic NO{sub x} removal assessed using both solar and visible-light lamps.

• OSTI ID: 22573932
• Journal Information: Journal of Solid State Chemistry, Vol. 231; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
AMMONIUM HYDROXIDES
CRYSTALS
DOPED MATERIALS
HEAT TREATMENTS
MICROSTRUCTURE
NANOPARTICLES
NANOSTRUCTURES
NITROGEN
NITROGEN OXIDES
PHOTOCATALYSIS
POWDERS
PRECIPITATION
RUTILE
SIMULATION
SOL-GEL PROCESS
SOLS
SYNTHESIS
TITANIUM
TITANIUM OXIDES
X RADIATION