Chemical diffusion analysis of the oxidation kinetics of oxygen-deficient, nitrogen doped TiO2 thin films

Misha Sinder, Jianmin Shi, Klaus Dieter Becker

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Modification of TiO2 by nitrogen-doping improves its photocatalytic efficiency in visible-light activated photocatalytic processes. Therefore, the defect structure and the point defect transport of N-doped TiO2 represent important fundamental issues. Shi et al. (2012) have studied the re-oxidation kinetics of chemically reduced N-doped TiO2 (anatase) thin films by means of in situ optical spectroscopy. It was found that the time dependence of optical absorbance due to oxidation follows a parabolic rate law. The present paper is devoted to further development and refinement of the kinetic model. The ambipolar chemical diffusion model accounts for three types of mobile charged point defects with essentially different diffusion coefficients (electrons, holes, and titanium interstitials) as well as for a uniformly distributed background of immobile nitrogen ions. The concentration profiles of diffusing species and oxygen activity profiles have been obtained by numerical as well as by approximate analytical solutions of the chemical diffusion equation. The profiles reveal the presence of two separate singularities: an electron-hole recombination reaction front and a step-like electron concentration front whose coordinate obeys a parabolic rate law.

Original languageEnglish
Article number115044
JournalSolid State Ionics
Volume341
DOIs
StatePublished - 5 Nov 2019

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics

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