title: Photoexcited Surface Frustrated Lewis Pairs for Heterogeneous Photocatalytic CO2 Reduction.
abstract: In this study we investigated, theoretically and experimentally, the unique photoactive behavior of pristine and defected indium oxide surfaces providing fundamental insights into their excited state properties as well as an explanation for the experimentally observed enhanced activity of defected indium oxide surfaces for the gas-phase reverse water gas shift reaction, CO2 + H2 + hν→ CO + H2O in the light compared to the dark. To this end, a detailed excited-state study of pristine and defected forms of indium oxide (In2O3, In2O3-x, In2O3(OH)y and In2O3-x(OH)y) surfaces was performed using time dependent density functional theory (TDDFT) calculations, the results of which were supported experimentally by transient absorption spectroscopy and photoconductivity measurements. It was found that the surface frustrated Lewis pairs (FLPs) created by a Lewis acidic coordinately unsaturated surface indium site proximal to an oxygen vacancy and a Lewis basic surface hydroxide site in In2O3-x(OH)y become more acidic and basic and hence more active in the ES compared to the GS. This provides a theoretical mechanism responsible for the enhanced activity and reduced activation energy of the photochemical reverse water gas shift reaction observed experimentally for In2O3-x(OH)y compared to the thermochemical reaction. This fundamental insight into the role of photoexcited surface FLPs for catalytic CO2 reduction could lead to improved photocatalysts for solar fuel production.
authors.affiliation: Department of Materials Science and Engineering, University of Toronto , 184 College Street, Suite 140, Toronto, Ontario M5S 3E4, Canada.
authors.forename: Kulbir Kaur
authors.initials: KK
authors.lastname: Ghuman
authors.affiliation: Department of Chemistry, University of Toronto , 80 St. George Street, Rm 326, Toronto, Ontario M5S 3E4, Canada.
authors.forename: Laura B
authors.initials: LB
authors.lastname: Hoch
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology , 901 Atlantic Drive, Atlanta, Georgia 30332-0400, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Szymanski
authors.affiliation: The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors.forename: Joel Y Y
authors.initials: JY
authors.lastname: Loh
authors.affiliation: Department of Materials Science and Engineering, University of Toronto , 184 College Street, Suite 140, Toronto, Ontario M5S 3E4, Canada.|The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
authors.forename: Nazir P
authors.initials: NP
authors.lastname: Kherani
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology , 901 Atlantic Drive, Atlanta, Georgia 30332-0400, United States.
authors.forename: Mostafa A
authors.initials: MA
authors.lastname: El-Sayed
authors.affiliation: Department of Chemistry, University of Toronto , 80 St. George Street, Rm 326, Toronto, Ontario M5S 3E4, Canada.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Ozin
authors.affiliation: Department of Materials Science and Engineering, University of Toronto , 184 College Street, Suite 140, Toronto, Ontario M5S 3E4, Canada.
authors.forename: Chandra Veer
authors.initials: CV
authors.lastname: Singh