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Lithium adsorption on TiO 2 : studies with electron spectroscopies (MIES and UPS)
Author(s) -
Krischok S.,
Schaefer J. A.,
Höfft O.,
Kempter V.
Publication year - 2005
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.2014
Subject(s) - chemistry , rutile , lithium (medication) , work function , adsorption , x ray photoelectron spectroscopy , ultraviolet photoelectron spectroscopy , desorption , analytical chemistry (journal) , ionic bonding , alkali metal , spectroscopy , band gap , inorganic chemistry , ion , electronic structure , materials science , computational chemistry , nuclear magnetic resonance , optoelectronics , organic chemistry , electrode , chromatography , quantum mechanics , endocrinology , medicine , physics
The adsorption of lithium atoms on rutile TiO 2 (110) single crystals was studied with metastable‐induced electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS(HeI)) between 130 K and room temperature. Some auxiliary measurements on W(110) required for data interpretation are also reported. At 130 K ionic adsorption at titania prevails up to 0.3 monolayer equivalents (MLE) as judged from the weak Li(2s) emission in MIES for these exposures. The reduction of the Ti 4+ cation is manifested by the growth of an occupied bandgap state in UPS: the alkali s‐electron is transferred to a near‐surface cation, thereby reducing it to Ti 3+ 3d. The transfer of the s‐electron is responsible for the observed work function decrease up to ∼0.5 MLE coverage. From the analysis of the UPS Ti 3+ 3d signal, as well as from the Li(2s) emission, it is concluded that the degree of ionicity of the adsorbed Li decreases from 100% at 0.3 MLE to 40% at 0.7 MLE. Above 0.5 MLE the MIES spectra are dominated by an Li(2s)‐induced peak indicating the presence of Li with an at least partially filled 2s orbital. At temperatures above 160 K this peak is almost absent. Excluding Li desorption at these temperatures, we suggest that Li moves into or below the rutile TiO 2 (110) surface above 160 K. Lithium insertion into the surface and intercalation are discussed. Copyright © 2004 John Wiley & Sons, Ltd.