This study reports the preparation of titanium (Ti3+) and nitrogen co-doped cubic ordered mesoporous TiO2 thin films using N2H4 treatment. The resulting co-doped TiO2 (Ti3+-N-TiO2) thin films show significant enhancements in visible light absorption and photocatalytic activity. Cubic ordered mesoporous TiO2 thin films were prepared via a sol-gel method with Pluronic F127 as the pore template. After brief calcination, the TiO2 films were dipped into hydrazine hydrate which acts both as a nitrogen source and as a reducing agent, followed by heating at low temperature (90 °C). The hydrazine treatment period was varied from 5 to 20 h to obtain different degrees of reduction and nitrogen doping. X-ray photoelectron spectroscopy (XPS) analyses and UV–vis absorbance spectra of Ti3+-N-TiO2 films indicate that the incorporated N atoms and Ti3+ reduce the band gap of TiO2 and thus enhance the absorption of visible light. The corresponding visible light photocatalytic activity of Ti3+-N-TiO2 films was determined from the photocatalytic degradation of methylene blue under visible light illumination (at 455 nm). The Ti3+-N-TiO2 films prepared with 10 h of treatment show the optimum photocatalytic activity, with a pseudo-first order rate coefficient of 0.12 h−1, which is 3 times greater than that of undoped TiO2 films. Calcination temperature and time were varied prior to hydrazine treatment to confirm that a brief calcination at low temperature (10 min at 350 °C) gave the best photochemical activity. In photoelectrochemical water oxidation using a 455 nm LED, the Ti3+-N-TiO2 films prepared with 10 h of N2H4 treatment show about 4 times the photocurrent compared to undoped TiO2 films. The present study suggests that hydrazine induced doping is a promising approach to enable synergistic incorporation of N and Ti3+ into the lattice of surfactant-templated TiO2 films and enhanced visible light photoactivity, but that the benefits are limited by gradual mesostructure deterioration.
|Number of pages||12|
|Journal||Materials Chemistry and Physics|
|State||Published - Oct 1 2016|
Bibliographical noteFunding Information:
Preliminary experiments to develop nitrogen doping and photocatalytic testing methods were performed as part of a U.S. Department of Energy EPSCoR Implementation award supported by grant no. DE-FG02-07-ER46375 . The detailed study as a function of hydrazine exposure time and further analysis of the spectroscopic and structural characteristics of the doped films was performed as part of an National Science Foundation EPSCoR Research Infrastructure Initiative award supported by grant no. IIA-1355438 . The authors thank Dr. Xudong Fan at Michigan State University for performing the TEM analysis of TiO 2 thin films and Prof. Y.T. Cheng for access to the XPS instrument at the University of Kentucky.
© 2016 Elsevier B.V.
- Chemical synthesis
- Electrochemical properties
- Non-crystalline materials
- Thin films
ASJC Scopus subject areas
- Materials Science (all)
- Condensed Matter Physics