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

Journal Article · Fri Feb 16 04:00:00 EST 2018 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.7b11266· OSTI ID:1462338

Delegan, N. ^[1]; Pandiyan, R. ^[1]; Johnston, S. ^[2]; Dirany, A. ^[3]; Komtchou, S. ^[3]; Drogui, P. ^[3]; El Khakani, M. A. ^[1]

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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

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.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1462338
• Report Number(s): NREL/JA-5K00-72060
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 10 Vol. 122; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
doping
optoelectronics
sputtering
thin films