title: Carrier dynamics and the role of surface defects: Designing a photocatalyst for gas-phase CO2 reduction.
abstract: In2O3-x(OH)ynanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO2to 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)ynanoparticles 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 CO2reduction.
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Hoch
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332.
authors.forename: Paul
authors.initials: P
authors.lastname: Szymanski
authors.affiliation: Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada M5S 3E4.
authors.forename: Kulbir Kaur
authors.initials: KK
authors.lastname: Ghuman
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6.
authors.forename: Le
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6.
authors.forename: Kristine
authors.initials: K
authors.lastname: Liao
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973.|Department of Physics, Temple University, Philadelphia, PA, 19122.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Qiao
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Reyes
authors.affiliation: Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332.
authors.forename: Mostafa A
authors.initials: MA
authors.lastname: El-Sayed
authors.affiliation: Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada M5S 3E4; chandraveer.singh@utoronto.ca gozin@chem.utoronto.ca.|Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada M5S 3G8.
authors.forename: Chandra Veer
authors.initials: CV
authors.lastname: Singh
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 3H6; chandraveer.singh@utoronto.ca gozin@chem.utoronto.ca.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Ozin
keywords: CO2 hydrogenation; indium oxide; solar fuels; surface defects; transient absorption