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Title: Remarkable Enhancement of Photocatalytic Water Oxidation in N 2 /Ar Plasma Treated, Mesoporous TiO 2 Films

Authors:
 [1];  [2];  [2];  [2];  [1]
  1. Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40506-0046, United States
  2. Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, United States
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1392735
Grant/Contract Number:
FG02-07-ER46375
Resource Type:
Journal Article: Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 26; Related Information: CHORUS Timestamp: 2017-11-02 14:26:20; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English

Citation Formats

Islam, Syed Z., Reed, Allen, Wanninayake, Namal, Kim, Doo Young, and Rankin, Stephen E. Remarkable Enhancement of Photocatalytic Water Oxidation in N 2 /Ar Plasma Treated, Mesoporous TiO 2 Films. United States: N. p., 2016. Web. doi:10.1021/acs.jpcc.6b02622.
Islam, Syed Z., Reed, Allen, Wanninayake, Namal, Kim, Doo Young, & Rankin, Stephen E. Remarkable Enhancement of Photocatalytic Water Oxidation in N 2 /Ar Plasma Treated, Mesoporous TiO 2 Films. United States. doi:10.1021/acs.jpcc.6b02622.
Islam, Syed Z., Reed, Allen, Wanninayake, Namal, Kim, Doo Young, and Rankin, Stephen E. 2016. "Remarkable Enhancement of Photocatalytic Water Oxidation in N 2 /Ar Plasma Treated, Mesoporous TiO 2 Films". United States. doi:10.1021/acs.jpcc.6b02622.
@article{osti_1392735,
title = {Remarkable Enhancement of Photocatalytic Water Oxidation in N 2 /Ar Plasma Treated, Mesoporous TiO 2 Films},
author = {Islam, Syed Z. and Reed, Allen and Wanninayake, Namal and Kim, Doo Young and Rankin, Stephen E.},
abstractNote = {},
doi = {10.1021/acs.jpcc.6b02622},
journal = {Journal of Physical Chemistry. C},
number = 26,
volume = 120,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.jpcc.6b02622

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  • In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen 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 hydrogen doping. UV-vis absorbance spectra indicate that H2 plasma treatment makes TiO2 films black, with broad-spectrum enhancement of visible lightmore » absorption, and XPS analysis shows peak for Ti3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO2) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO2 is accompanied by significant hydrogen uptake and not just Ti3+ generation or surface disordering.« less
  • Nitrogen-doped TiO{sub 2} catalysts were prepared by a precipitation method. The samples were calcined at 400 deg. C for 4 h in air. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature N{sub 2}-adsorption was used for structural characterization and UV-diffuse reflectance (UV-DR) was applied to investigate the optical properties of the as-prepared samples. It was found that microporous N-doped catalysts have solely anatase crystalline structure. Acidic treatment of the calcined samples was performed using sulfuric acid agitation. The crystalline structure remained unchanged due to surface treatment, while the porosity and the surface areas (a{sub BET}{sup S}) were decreased dramatically.more » Optical characterization of the doped catalysts showed that they could be excited by visible light photons in the 400-500 nm wavelength range (lambda{sub g,1}={approx}390 nm, lambda{sub g,2}={approx}510 nm). It was also established that surface treatment enhances the Vis-light absorption of the N-TiO{sub 2} powders. Finally the catalysts were tested in the photocatalytic degradation of phenol in aqueous suspensions. Two different light sources were used; one of them was a UV-rich high pressure Hg-lamp, while the other was a tubular visible light source. We found that using visible light illumination N-doped, acid treated TiO{sub 2} samples were more catalytically active than non-doped TiO{sub 2} catalysts. - Graphical abstract: The effect of the acid treatment on the visible-light-driven photocatalytic activity of the N-doped, anatase TiO{sub 2} catalysts.« less
  • Partly ordered mesoporous titania films with anatase crystallites incorporated into the pore walls were prepared at low temperature by spin-coating a microemulsion-based reaction solution. The effect of relative humidity employed during aging of the prepared films was studied using SEM, TEM, and grazing incidence small angle X-ray scattering to evaluate the mesoscopic order, porosity, and crystallinity of the films. The study shows unambiguously that crystal growth occurs mainly during storage of the films and proceeds at room temperature largely depending on relative humidity. Porosity, pore size, mesoscopic order, crystallinity, and photocatalytic activity of the films increased with relative humidity upmore » to an optimum around 75%.« less
  • Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and electron energy loss spectroscopy (EELS) have been used to examine the consequences of the interaction of radio frequency water plasmas with polycrystalline tin oxide surfaces. Results from AR-XPS and EELS indicate that an extensive surface hydroxylation or gel layer (> 10 {angstrom}) does not form on the tin oxide surface from exposure to atmosphere and/or water plasma treatment. Surface hydroxyl coverages determined by AR-XPS are a factor of 3 lower than those calculated from crystallographic models. Annealing of water plasma treated tin oxide films in ultrahigh vacuum results in the desorption of water, dehydroxylationmore » of the surface, and creation of oxygen vacancies. AR-XPS data indicate a uniform concentration of oxygen vacancies over a sampling depth of approximately 15 {angstrom}. Water plasma treatment of oxygen-deficient tin oxide surfaces created by annealing in ultrahigh vacuum eliminates oxygen vacancies and restores Sn{sup 4+} valency in the surface region.« less