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Title: Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO 2 Nanoparticles

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1];  [1]
  1. Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Argonne-Northwestern Solar Energy Research Center (ANSER)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1388133
DOE Contract Number:
SC0001059
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 139; Journal Issue: 8; Related Information: ANSER partners with Northwestern University (lead); Argonne National Laboratory; University of Chicago; University of Illinois, Urbana-Champaign; Yale University
Country of Publication:
United States
Language:
English
Subject:
catalysis (homogeneous), catalysis (heterogeneous), solar (photovoltaic), solar (fuels), photosynthesis (natural and artificial), bio-inspired, hydrogen and fuel cells, electrodes - solar, defects, charge transport, spin dynamics, membrane, materials and chemistry by design, optics, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Peper, Jennifer L., Vinyard, David J., Brudvig, Gary W., and Mayer, James M. Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO 2 Nanoparticles. United States: N. p., 2017. Web. doi:10.1021/jacs.6b12112.
Peper, Jennifer L., Vinyard, David J., Brudvig, Gary W., & Mayer, James M. Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO 2 Nanoparticles. United States. doi:10.1021/jacs.6b12112.
Peper, Jennifer L., Vinyard, David J., Brudvig, Gary W., and Mayer, James M. Mon . "Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO 2 Nanoparticles". United States. doi:10.1021/jacs.6b12112.
@article{osti_1388133,
title = {Slow Equilibration between Spectroscopically Distinct Trap States in Reduced TiO 2 Nanoparticles},
author = {Peper, Jennifer L. and Vinyard, David J. and Brudvig, Gary W. and Mayer, James M.},
abstractNote = {},
doi = {10.1021/jacs.6b12112},
journal = {Journal of the American Chemical Society},
number = 8,
volume = 139,
place = {United States},
year = {Mon Feb 13 00:00:00 EST 2017},
month = {Mon Feb 13 00:00:00 EST 2017}
}
  • Highlights: • Spherical mesoporous TiO{sub 2} materials were obtained by a simple sol–gel method. • Physical mixture of TiO{sub 2} nanoparticle and mesoporous TiO{sub 2} was utilized for solar cell electrode. • Mixed electrode system exhibited higher DSSC performance. - Abstract: There are two factors on the efficiency of dye-sensitized solar cell (DSSC): one is the amount of dye adsorbed, and the other is contact resistance. In this study, TiO{sub 2} nanoparticles (nano-TiO{sub 2}, about 20 nm particle size) were infiltrated between mesoporous TiO{sub 2} (meso-TiO{sub 2}) particles with about 300 nm particle sizes, in order to reduce the contactmore » resistance of TiO{sub 2} electrodes. The infiltrated nano-TiO{sub 2} can facilitate electron transfer between meso-TiO{sub 2} particles by filling the empty volume of DSSC electrodes. As a result, the TiO{sub 2} electrode containing 65 wt% of meso-TiO{sub 2} and 35 wt% of nano-TiO{sub 2} exhibited the highest performance of DSSC.« less
  • The nucleation and growth of Pt nanoparticles (NP’s) on rutile TiO{sub 2} (110) surfaces with O on-top atoms (oxidized TiO{sub 2}), surface O vacancies, and H adatoms, respectively (reduced TiO{sub 2}), was studied by means of scanning tunneling microscopy (STM) experiments and density functional theory calculations. At room temperature, Pt was found to be trapped at O on-top atoms and surface O vacancies, leading to rather small Pt NP’s. In contrast, on surfaces with H adatoms the mobility of Pt was much larger. As a result, large Pt NP's were found at room temperature on TiO{sub 2} (110) surfaces withmore » H adatoms. However, at ∼150 K the diffusion of Pt was kinetically hindered on all TiO{sub 2} (110) surfaces considered. STM data acquired after vacuum-annealing at 800 K showed comparable results on all TiO{sub 2} (110) surfaces because the diffusion of Pt is not influenced by surface defects at such high temperatures.« less
  • In this report, local electronic structures of steps and terraces on rutile TiO{sub 2} single crystal faces were studied by second harmonic and sum frequency generation (SHG/SFG) spectroscopy. We attained selective measurement of the local electronic states of the step bunches formed on the vicinal (17 18 1) and (15 13 0) surfaces using a recently developed step-selective probing technique. The electronic structures of the flat (110)-(1x1) (the terrace face of the vicinal surfaces) and (011)-(2x1) surfaces were also discussed. The SHG/SFG spectra showed that step structures are mainly responsible for the formation of trap states, since significant resonances frommore » the trap states were observed only from the vicinal surfaces. We detected deep hole trap (DHT) states and shallow electron trap (SET) states selectively from the step bunches on the vicinal surfaces. Detailed analysis of the SHG/SFG spectra showed that the DHT and SET states are more likely to be induced at the top edges of the step bunches than on their hillsides. Unlike the SET states, the DHT states were observed only at the step bunches parallel to [1 1 1][equivalent to the step bunches formed on the (17 18 1) surface]. Photocatalytic activity for each TiO{sub 2} sample was also measured through methylene blue photodegradation reactions and was found to follow the sequence: (110) < (17 18 1) < (15 13 0) < (011), indicating that steps along [0 0 1] are more reactive than steps along [1 1 1]. This result implies that the presence of the DHT states observed from the step bunches parallel to [1 1 1] did not effectively contribute to the methylene blue photodegradation reactions.« less
  • A 5 wt % MoO{sub 3}/TiO{sub 2} catalyst was reduced in hydrogen at various temperatures to produce a surface with average Mo oxidation states between +6 and 0. The changes in molybdenum oxidation states as a function of the extent of reduction were monitored by gravimetric analyses and x-ray photoelectron spectroscopy (XPS, ESCA), and the results were correlated with benzene hydrogenation activity. ESCA Mo 3d{sub 5/2} binding energy values for the various Mo oxidation states on a 5 wt % MoO{sub 3}/TiO{sub 2} catalyst show a shift of 5.1 eV between Mo{sup +6} (232.7 eV) and Mo{sup 0} (227.6 eV).more » The benzene hydrogenation activity was found to depend strongly on the extent of reduction of the Mo phase. Comparison of benzene hydrogenation activity with the distribution of Mo oxidation states determined by ESCA suggests that molybdenum ions with an oxidation state of +2 are the most active species.« less