Effect of O2 and CO Exposure on the Photoelectron Spectroscopy of Size-Selected Pdn Clusters Supported on TiO2(110)

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• 作者：Arthur C. Reber ; Shiv N. Khanna ; F. Sloan Roberts ; Scott L. Anderson
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 4, 2016
• 年：2016
• 卷：120
• 期：4
• 页码：2126-2138
• 全文大小：770K
• ISSN：1932-7455

文摘

Ultraviolet photoelectron spectroscopy of size-selected Pd_n clusters supported on TiO₂ shows a decrease in density of states in the TiO₂ gap after the absorption of CO, while O₂ does not result in a decrease in density. Oxygen is more electron withdrawing than CO, so the Pd clusters should become more positively charged when exposed to O₂ than CO. More positively charged clusters are expected to have larger electron binding energies; thus, the observed shifts in the UPS spectra are at odds with conventional wisdom. We have performed a combined experimental and theoretical investigation of the UPS spectra of Pd_n clusters with adsorbed O₂ and CO. Bonding of both CO molecules and O atoms to the Pd clusters results in a decrease in the density of states in the TiO₂ gap; however, O atom binding on top of the clusters also results in significant final state stabilization, restoring the density of states in the TiO₂ gap. We also find that 4d–5s hybridization plays a critical role in the initial state energies in X-ray photoelectron spectroscopy and evaluate two methods for determining the final state shift via periodic calculations.