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Title: Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO 2 reduction

In 2O 3-x(OH) y nanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO 2 to CO via the reverse water–gas shift reaction. Their photocatalytic activity is strongly correlated to the number of oxygen vacancy and hydroxide defects present in the system. To better understand how such defects interact with photogenerated electrons and holes in these materials, we have studied the relaxation dynamics of In 2O 3-x(OH) y nanoparticles with varying concentration of defects using two different excitation energies corresponding to above-band-gap (318-nm) and near-band-gap (405-nm) excitations. Our results demonstrate that defects play a significant role in the excited-state, charge relaxation pathways. Higher defect concentrations result in longer excited-state lifetimes, which are attributed to improved charge separation. This correlates well with the observed trends in the photocatalytic activity. These results are further supported by density-functional theory calculations, which confirm the positions of oxygen vacancy and hydroxide defect states within the optical band gap of indium oxide. This enhanced understanding of the role these defects play in determining the optoelectronic properties and charge carrier dynamics can provide valuable insight toward the rational development of more efficient photocatalytic materials for CO 2 reduction.
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [3] ;  [1] ;  [4] ;  [2] ;  [1] ;  [1]
  1. Univ. of Toronto, Toronto, ON (Canada)
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States); Temple Univ., Philadelphia, PA (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
BNL-113550-2017-JA
Journal ID: ISSN 0027-8424; R&D Project: MA015MACA
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 50; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; indium oxide; solar fuels; CO2 hydrogenation; transient absorption; surface defects
OSTI Identifier:
1345732

Hoch, Laura B., Szymanski, Paul, Ghuman, Kulbir Kaur, He, Le, Liao, Kristine, Qiao, Qiao, Reyes, Laura M., Zhu, Yimei, El-Sayed, Mostafa A., Singh, Chandra Veer, and Ozin, Geoffrey A.. Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO2 reduction. United States: N. p., Web. doi:10.1073/pnas.1609374113.
Hoch, Laura B., Szymanski, Paul, Ghuman, Kulbir Kaur, He, Le, Liao, Kristine, Qiao, Qiao, Reyes, Laura M., Zhu, Yimei, El-Sayed, Mostafa A., Singh, Chandra Veer, & Ozin, Geoffrey A.. Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO2 reduction. United States. doi:10.1073/pnas.1609374113.
Hoch, Laura B., Szymanski, Paul, Ghuman, Kulbir Kaur, He, Le, Liao, Kristine, Qiao, Qiao, Reyes, Laura M., Zhu, Yimei, El-Sayed, Mostafa A., Singh, Chandra Veer, and Ozin, Geoffrey A.. 2016. "Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO2 reduction". United States. doi:10.1073/pnas.1609374113. https://www.osti.gov/servlets/purl/1345732.
@article{osti_1345732,
title = {Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO2 reduction},
author = {Hoch, Laura B. and Szymanski, Paul and Ghuman, Kulbir Kaur and He, Le and Liao, Kristine and Qiao, Qiao and Reyes, Laura M. and Zhu, Yimei and El-Sayed, Mostafa A. and Singh, Chandra Veer and Ozin, Geoffrey A.},
abstractNote = {In2O3-x(OH)y nanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO2 to CO via the reverse water–gas shift reaction. Their photocatalytic activity is strongly correlated to the number of oxygen vacancy and hydroxide defects present in the system. To better understand how such defects interact with photogenerated electrons and holes in these materials, we have studied the relaxation dynamics of In2O3-x(OH)y nanoparticles with varying concentration of defects using two different excitation energies corresponding to above-band-gap (318-nm) and near-band-gap (405-nm) excitations. Our results demonstrate that defects play a significant role in the excited-state, charge relaxation pathways. Higher defect concentrations result in longer excited-state lifetimes, which are attributed to improved charge separation. This correlates well with the observed trends in the photocatalytic activity. These results are further supported by density-functional theory calculations, which confirm the positions of oxygen vacancy and hydroxide defect states within the optical band gap of indium oxide. This enhanced understanding of the role these defects play in determining the optoelectronic properties and charge carrier dynamics can provide valuable insight toward the rational development of more efficient photocatalytic materials for CO2 reduction.},
doi = {10.1073/pnas.1609374113},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 50,
volume = 113,
place = {United States},
year = {2016},
month = {11}
}