Presentation Title

Oxygen depletion on TiO2 brookite nanoparticle surfaces and implications for photocatalysis and solar energy conversion

Start Date

November 2016

End Date

November 2016

Location

Watkins 1111

Type of Presentation

Oral Talk

Abstract

Titanium dioxide (TiO2) is one of the most studied metal oxides due to its use in many fields, notably photocatalysis and solar energy conversion. Surface reactivity and thus the efficacy of TiO2 as a heterogeneous catalyst is greatly affected by stoichiometric deviations at the surface due to localized oxygen depletion. Two of the crystallographic forms of TiO2, anatase and rutile, have been extensively studied. Due to difficulty preparing macroscale samples, the third phase, brookite, has not been well characterized, though recent studies suggest brookite has increased photocatalytic ability compared to the other two forms. In this study TiO2 nanopowders consisting of mostly brookite were synthesized by laser evaporation and the extent of oxygen depletion was analyzed by nuclear reaction analysis. Density functional calculations are coupled with these experimental studies to examine the geometry and electronic structure of three oxygen-depleted brookite surfaces, (210), (010), and (001) representing the lowest energy terminations likely present in a brookite sample. Geometry optimizations and density of states analyses revealed that Ti atoms present on oxygen-depleted surfaces tend to relax toward the interior oxide and approximate metallic geometry and electronic structure. Both experimental and ab initio results therefore indicate the surface of the synthesized TiO2 nanopowders is markedly metallic in character due to localized oxygen depletion. These results and the possibility of tunable surface stoichiometry hold significant implications for the use of brookite in surface chemistry applications of catalysis and solar materials.

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Nov 12th, 10:00 AM Nov 12th, 10:15 AM

Oxygen depletion on TiO2 brookite nanoparticle surfaces and implications for photocatalysis and solar energy conversion

Watkins 1111

Titanium dioxide (TiO2) is one of the most studied metal oxides due to its use in many fields, notably photocatalysis and solar energy conversion. Surface reactivity and thus the efficacy of TiO2 as a heterogeneous catalyst is greatly affected by stoichiometric deviations at the surface due to localized oxygen depletion. Two of the crystallographic forms of TiO2, anatase and rutile, have been extensively studied. Due to difficulty preparing macroscale samples, the third phase, brookite, has not been well characterized, though recent studies suggest brookite has increased photocatalytic ability compared to the other two forms. In this study TiO2 nanopowders consisting of mostly brookite were synthesized by laser evaporation and the extent of oxygen depletion was analyzed by nuclear reaction analysis. Density functional calculations are coupled with these experimental studies to examine the geometry and electronic structure of three oxygen-depleted brookite surfaces, (210), (010), and (001) representing the lowest energy terminations likely present in a brookite sample. Geometry optimizations and density of states analyses revealed that Ti atoms present on oxygen-depleted surfaces tend to relax toward the interior oxide and approximate metallic geometry and electronic structure. Both experimental and ab initio results therefore indicate the surface of the synthesized TiO2 nanopowders is markedly metallic in character due to localized oxygen depletion. These results and the possibility of tunable surface stoichiometry hold significant implications for the use of brookite in surface chemistry applications of catalysis and solar materials.