Cu-Enhanced Surface Defects and Lattice Mobility of Pr-CeO2 Mixed Oxides

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• 作者：Anita M. D’Angelo ; Zili WuSteven H. Overbury ; Alan L. Chaffee
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 15, 2016
• 年：2016
• 卷：120
• 期：49
• 页码：27996-28008
• 全文大小：792K
• ISSN：1932-7455

文摘

The surface properties of CeO₂, Pr-CeO₂, and 5% and 15% Cu-doped Pr-CeO₂ were investigated using methanol as a probe molecule through adsorption and desorption studies carried out using in situ DRIFTS. It was revealed that the surfaces of the 5% and 15% Cu materials were dominated by reduced cations/vacancies and that the 15% Cu material contained the highest concentration of these active species. The high oxygen storage capacity (OSC) of the 15% Cu material, as determined using TGA, reflects the available vacant sites for oxygen adsorption. Formates were formed on all materials, with those formed on the Cu-doped materials present at temperatures as low as 25 °C, hence showing their superior reactivity toward methoxy oxidation. During formate dehydrogenation, H₂, CO, CO₂, and H₂O evolved as the surface cations were simultaneously reduced. It was also observed that, for the Cu-containing materials, H₂ was not formed and the high surface mobility determined through isotopic exchange simultaneously generated CO and CO₂. The exhibited high surface mobility, surface vacancies, and OSC of the 15% Cu material can be attributed to the formation of a secondary copper oxide phase observed using SEM-EDX spectroscopy. These results highlight the importance of surface defects in contrast to bulk defects.