Improved catalysts with properties controlled by semiconductor band engineering

Chua, Yong Ping Gavin

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https://hdl.handle.net/2142/46736 Copy

Description

Title

Improved catalysts with properties controlled by semiconductor band engineering

Author(s)

Chua, Yong Ping Gavin

Issue Date

2014-01-16T18:00:44Z

Director of Research (if dissertation) or Advisor (if thesis)

• Seebauer, Edmund G.
• Saeys, Mark

Doctoral Committee Chair(s)

Kenis, Paul J.A.

Committee Member(s)

• Yan, Ning
• Seebauer, Edmund G.
• Saeys, Mark
• Jiang, Jianwen
• Yang, Hong

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Catalyst
• platinum
• semiconductor band engineering

Abstract

Difficulties in achieving control over carrier concentration have impeded progress toward tailoring the carrier concentration in semiconducting oxide supports for metal catalysts. Such tailoring could make possible the intentional exploitation of the Schwab effect, in which the carrier concentration in the semiconducting support affects reaction rate on the supported metal catalyst. An atomic layer deposition synthesis technique developed in the Seebauer lab allows variation of thin polycrystalline anatase TiO2 film thickness that provides an unconventional means of varying carrier concentration. The film thickness has an inverse relationship with its carrier concentration, as an increase in film thickness reduces the concentration of electrically active grain boundaries, locations where native donor defects aggregate. These TiO2 films were sputtered with small amounts of Pt and ran under a CO oxidation test reaction to demonstrate the electronic influence of the TiO2 support on Pt catalytic activity. Over a range of TiO2 film thickness corresponding to carrier concentrations that varied by a factor of around 10, the reaction rate coefficient kCO in excess CO increased by about 70% while the rate coefficient kO2 in excess O2 decreased by 30%. This can be rationalized by the extent of electron injection from the TiO2 support into Pt. Increased electron injection into Pt, due to increased TiO2 carrier concentration, decreases Pt-CO binding strengthand an increase in reaction rate in excess CO and a rate decrease in excess O2. Photoelectron spectroscopy studies have shown that the valence electron distribution of Pt/TiO2 near the Fermi level varies as a function of TiO2 carrier concentration changes (due to TiO2 film thickness variation), even as Pt remains constant at its Pt0 chemical state.

Graduation Semester

2013-12

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http://hdl.handle.net/2142/46736

Copyright and License Information

Copyright 2013 Yong Ping Gavin Chua

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