Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 115, Issue 45, Pages 22400-22408Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp2065024
Keywords
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Funding
- Army Research Office [W911NF-09-1-0150]
- Defense Threat Reduction Agency [W911NF-06-1-0111]
- Department of Energy, Office of Basic Energy Sciences [DE-FG02-09ER16080]
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Transmission Fourier transform infrared spectroscopy, coupled with CO adsorption, was used to study how the oxidation state of Au surface sites change during H-2 dissociation, migration, and electronic excitation of TiO2 in a nanoparticulate Au/TiO2 catalyst. Data reveals that atomic H, produced by H-2 dissociation on Au particles, readily hydroxylates the Au-O-Ti linkages around the periphery of the gold particles. Following passivation of peripheral sites, the H atoms diffuse into the bulk of the titania where they protonate the semiconductor, while donating an electron to shallow trapped (ST) states just below the conduction band (CB). The donated electrons effectively n-dope the semiconductor. By simultaneously monitoring changes in the infrared absorbance due to transitions involving ST electrons, free CB electrons, and the fundamental stretching mode of CO(a), we have found that the most active sites for hydrogen dissociation are Au-0 sites at the free step edges or other defect sites in the Au nanoparticles that are located away from the Au-O-Ti interface.
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