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Title: Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO 2 :WN Thin Films

Abstract

We report on one-step in situ codoped TiO2 thin films synthesized by cosputtering. The purpose of this acceptor-donor passivated codoping approach is to overcome the optoelectronic limitations that arise for monodoped TiO2 in photocatalytic applications. To evaluate these added benefits, the TiO2:WN thin films were characterized by different techniques. X-ray diffraction patterns and X-ray photoelectron spectral analysis revealed that both N and W dopants are mostly present in the desired substitutional locations. Additionally, the codoping approach was found to reduce the internal strain and defect density of the TiO2:WN films as compared to their monodoped TiO2:N counterparts. This defect reduction is confirmed via photocharge lifetime variation obtained using visible light flash photolysis time-resolved microwave conductivity measurements (FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes: charge trapping, recombination, and surface reactions. These characteristic lifetimes of the codoped TiO2:WN films (i.e., 0.08, 0.75, and 11.5 us, respectively) were found to be about double those of their nitrogen monodoped TiO2:N counterparts (i.e., 0.03, 0.35, and 6.8 us), quantitatively confirming the effective passivating outcome of the tungsten-nitrogen codoping approach developed here. The practicality of this method was confirmed by integrating the TiO2:WN films as photoanodes for the electro-photocatalytic, solar lightmore » driven degradation of a real pollutant (i.e., atrazine). A significant increase in the degradation kinetics, leading to a 4-fold increase in the pseudo-first-order degradation constant for the optimally doped TiO2:WN photoanodes (0.106 min-1) from the undoped TiO2-x ones (0.026 min-1), is a direct consequence of the increased photocharge lifetimes in tandem with visible light photosensitivity.« less

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [3];  [3];  [1]
  1. Centre-Énergie, Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Blvd. Lionel-Boulet, Varennes, QC J3X-1S2, Canada
  2. National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401-3393, United States
  3. Centre-Eau, Terre et Environnement, Institut National de la Recherche Scientifique, 490 Rue de la Couronne, Québec City, QC G1K-9A9, Canada
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1462338
Report Number(s):
NREL/JA-5K00-72060
Journal ID: ISSN 1932-7447
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 10; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; thin films; doping; sputtering; optoelectronics

Citation Formats

Delegan, N., Pandiyan, R., Johnston, S., Dirany, A., Komtchou, S., Drogui, P., and El Khakani, M. A. Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO 2 :WN Thin Films. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.7b11266.
Delegan, N., Pandiyan, R., Johnston, S., Dirany, A., Komtchou, S., Drogui, P., & El Khakani, M. A. Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO 2 :WN Thin Films. United States. doi:10.1021/acs.jpcc.7b11266.
Delegan, N., Pandiyan, R., Johnston, S., Dirany, A., Komtchou, S., Drogui, P., and El Khakani, M. A. Fri . "Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO 2 :WN Thin Films". United States. doi:10.1021/acs.jpcc.7b11266.
@article{osti_1462338,
title = {Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogen in situ Codoped TiO 2 :WN Thin Films},
author = {Delegan, N. and Pandiyan, R. and Johnston, S. and Dirany, A. and Komtchou, S. and Drogui, P. and El Khakani, M. A.},
abstractNote = {We report on one-step in situ codoped TiO2 thin films synthesized by cosputtering. The purpose of this acceptor-donor passivated codoping approach is to overcome the optoelectronic limitations that arise for monodoped TiO2 in photocatalytic applications. To evaluate these added benefits, the TiO2:WN thin films were characterized by different techniques. X-ray diffraction patterns and X-ray photoelectron spectral analysis revealed that both N and W dopants are mostly present in the desired substitutional locations. Additionally, the codoping approach was found to reduce the internal strain and defect density of the TiO2:WN films as compared to their monodoped TiO2:N counterparts. This defect reduction is confirmed via photocharge lifetime variation obtained using visible light flash photolysis time-resolved microwave conductivity measurements (FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes: charge trapping, recombination, and surface reactions. These characteristic lifetimes of the codoped TiO2:WN films (i.e., 0.08, 0.75, and 11.5 us, respectively) were found to be about double those of their nitrogen monodoped TiO2:N counterparts (i.e., 0.03, 0.35, and 6.8 us), quantitatively confirming the effective passivating outcome of the tungsten-nitrogen codoping approach developed here. The practicality of this method was confirmed by integrating the TiO2:WN films as photoanodes for the electro-photocatalytic, solar light driven degradation of a real pollutant (i.e., atrazine). A significant increase in the degradation kinetics, leading to a 4-fold increase in the pseudo-first-order degradation constant for the optimally doped TiO2:WN photoanodes (0.106 min-1) from the undoped TiO2-x ones (0.026 min-1), is a direct consequence of the increased photocharge lifetimes in tandem with visible light photosensitivity.},
doi = {10.1021/acs.jpcc.7b11266},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 10,
volume = 122,
place = {United States},
year = {2018},
month = {2}
}