Effect of N-doping on the photocatalytic activity of sol-gel TiO 2

Nicholas T. Nolan, Damian W. Synnott, Michael K. Seery, Steven J. Hinder, Axel Van Wassenhoven, Suresh C. Pillai*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

162 Citations (Scopus)

Abstract

In order to study the visible light photocatalytic activity of nitrogen doped titanium dioxide, the interaction between nitrogen dopant sources and titania precursors during sol-gel synthesis is investigated. N-TiO 2 was synthesised using the sol-gel method using 1,3-diaminopropane as a nitrogen source. Samples were annealed several temperatures and the percentage of rutile present determined by X-ray diffraction to be 0% (500°C), 46% (600°C), and 94% (700°C). The reducing amounts of anatase at higher temperatures are studied using FTIR, which suggests the absence of any polymeric chains formed by the chelating agents, which would normally extend anatase-to-rutile transformation temperatures. Differential scanning calorimetry shows that crystalliation occurs before 500°C, providing the crystalline form determined by XRD at 500°C. Increased temperature also resulted in diminished visible light absorption capability, with only the 500°C sample showing significant absorption in the visible region. XPS studies revealed that nitrogen remained within the TiO 2 lattice at higher temperatures. Consequent with the reduced visible light absorption capacity, photocatalytic activity also reduced with increased annealing temperature. Degradation kinetics of methylene blue, irradiated with a 60W house-bulb, resulted in first order degradation rates constants of 0.40×10 -2, 0.19×10 -2, and 0.22×10 -2min -1 for 500, 600, and 700°C respectively. Degradation of Degussa P25 was minimal under the same conditions, and that of undoped TiO 2 was 0.02×10 -2min -1. Similarly, using 4-chlorophenol under solar irradiation conditions, the N-doped sample at 500°C substantially out-performed the undoped sample. These results are discussed in the context of the effect of increasing temperature on the nature of the band gap.

Original languageEnglish
Pages (from-to)88-94
Number of pages7
JournalJournal of Hazardous Materials
Volume211-212
DOIs
Publication statusPublished - Apr 15 2012
Externally publishedYes

Keywords

  • Band gap widening
  • Degussa p25
  • Mechanism of doping
  • N-doping
  • Photocatalytic activity
  • Semiconductor photocatalysis
  • Sol-gel and TiO
  • Visible light activity

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

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