Surface Acidity and Properties of TiO2/SiO2 Catalysts Prepared by Atomic Layer Deposition: UV-visible Diffuse Reflectance, DRIFTS, and Visible Raman Spectroscopy Studies

Lu, Junling; Kosuda, Kathryn M.; Van Duyne, Richard P.; Stair, Peter C.

Surface Acidity and Properties of TiO2/SiO2 Catalysts Prepared by Atomic Layer Deposition: UV-visible Diffuse Reflectance, DRIFTS, and Visible Raman Spectroscopy Studies

Active / Technical Report | Accession Number: ADA604390 |

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Abstract:

Highly uniform submonolayer to multilayer thin films of titanium dioxide supported on high surface area silica gel have been synthesized by atomic layer deposition ALD using titanium tetrachloride TiCl4 and titanium isopropoxide TTIP as metal precursors. The deposition rate of titania films from TiCl4 was found to be stable in the 150-300 deg C temperature range, which is slightly higher than that from TTIP at 150 deg C. UV-visible diffuse reflectance spectroscopy DRS shows that the coordination geometry of Ti cations depends on the number of ALD cycles and the precursor but is essentially independent of deposition temperature. Using diffuse reflectance infrared Fourier transform spectroscopy DRIFTS and visible Raman spectroscopy with pyridine as a probe molecule, we found all of the titania films studied to exhibit Lewis acidity but only films containing chloride or carbonyl impurities possessed Br nsted acid sites. Additionally, three new pronounced bands in the Raman spectra, 6b 638 cm-1, 9a 1200 cm-1, and 2 3103 cm-1, provide strong spectroscopic evidence for Br nsted acid sites on the surface.

Author(s):

Lu, Junling ; Kosuda, Kathryn M. ; Van Duyne, Richard P. ; Stair, Peter C.

Author Organization(s):

NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY

Descriptive Note:

Journal article

Supplementary Note:

Published in the Journal of Physical Chemistry C, v113 p12412-12418, 2009. Supported in part by DTRA and the Department of Energy Grant no. DE-FG02-97ER14789.

Pagination:

0008

Security Markings

DOCUMENT & CONTEXTUAL SUMMARY

Distribution:

Approved For Public Release

Distribution Statement:

Approved For Public Release; Distribution Is Unlimited.

RECORD

Collection: TR

Identifying Numbers

Contract/Grant Number(s):

FA9550-07-1-0526, FA9550-06-1-0558

Monitor Series:

AFOSR

Subject Terms

Joint Capability Areas:

JCA_6.3.3_Spectrum Management; JCA_6_Net Centric; JCA_6.3_Net Management; JCA_1_Force Support; JCA_1.2_Force Preparation; JCA_8_Building Partnerships; JCA_1.2.3_Educating; JCA_1.2.5_Lessons Learned; JCA_8.2_Shape

Modernization Areas:

Microelectronics

Communities of Interest:

Advanced Electronics

Descriptor(s):

*ACIDS, *DIFFUSE REFLECTION, *RAMAN SPECTROSCOPY, *SURFACE PROPERTIES, ATOMIC LAYER EPITAXY, DEPOSITION, DIOXIDES, MOLECULES, PROBES, PYRIDINES, RAMAN SPECTRA, SILICA GELS, THIN FILMS, TITANIUM COMPOUNDS

Field(s)/Group(s):

Organic Chemistry, Physical Chemistry, Atomic and Molecular Physics and Spectroscopy, Optics

Keyword(s):

BRONSTED ACID SITES, DRIFTS(DIFFUSE REFLECTANCE INFRARED FOURIER TRANSFORM SPECTROSCOPY), TICL4(TITANIUM TETRACHLORIDE), TTIP(TITANIUM ISOPROPOXIDE)

Report Date:

2009 Jun 15

Creation Date:

2014 Aug 13