Mesoporous TiO2 films treated with N2/argon plasma were studied for ultraviolet and visible-light-induced photocatalytic water oxidation activity. Compared to pristine TiO2 films, plasma-treated TiO2 films showed remarkable enhancement of photocurrents (up to 80-240 times) in both ultraviolet light and visible light, greatly surpassing enhancements previously reported in the literature. The cubic-ordered mesoporous TiO2 thin films were prepared by a surfactant-templated sol-gel method and were treated with N2/argon plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient nitrogen doping. The effects of reaction gas pressure and N2 gas flow rate on photoelectrochemical (PEC) response were investigated. UV-vis absorbance spectra indicated that the incorporated N atoms significantly reduced the band gap of TiO2 with the enhancement of visible-light absorption, and XPS analysis showed primarily substitutional N atom incorporation rather than interstitial. The photocatalytic activity of nitrogen-doped TiO2 (N-TiO2) films was evaluated by chronoamperometry and linear sweep voltammetry. The effect of light sources on PEC performance was explored using UV (365 nm), blue (455 nm), and green (530 nm) LEDs. N-TiO2 films showed 242× and 240× enhancement of photocurrent, compared to undoped TiO2 films under UV and blue LED irradiation, respectively. The N-doped films also showed overall enhancement of up to 70× and 92× with a broad spectrum Xe arc lamp and halogen bulb, respectively, and photocatalytic activity even with green LED illumination, compared to no measurable activity without doping. The present study shows that plasma-induced doping of sol-gel materials enables the efficient incorporation of heteroatoms into disordered metal oxide nanostructures, thereby leading to remarkable enhancement in visible-light-driven photoelectrochemical water oxidation.
|Number of pages||13|
|Journal||Journal of Physical Chemistry C|
|State||Published - Jul 7 2016|
Bibliographical noteFunding Information:
The authors acknowledge financial support from University of Kentucky faculty start-up funds (DYK). Experiments to develop the mesoporous titania film synthesis approach 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 plasma parameters, further analysis of the spectroscopic and structural characteristics of the doped films, and water oxidation experiments were performed as part of a National Science Foundation EPSCoR Researc Infrastructure Initiative award supported by grant no. IIA-1355438. Finally, the authors thank Prof. Y.T. Cheng, Prof. Dibakar Bhattacharyya and Andrew Colburn, and Prof. Brad Berron and Ishan Fursule, Prof. Anne- Frances Miller and Dr. Rupam Sarma, and Prof. Vijay Singh and Sai Guduru for access and assistance with the XPS, zeta potential, contact angle measurements, oxygen measurement, and water oxidation using the Xe arc lamp, respectively.
© 2016 American Chemical Society.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Energy (all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films