A First-Principle Study of Synergized O2 Activation and CO Oxidation by Ag Nanoparticles on TiO2(101) Support

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• 作者：Chuanyi Jia ; Guozhen Zhang ; Wenhui Zhong ; Jun Jiang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：April 27, 2016
• 年：2016
• 卷：8
• 期：16
• 页码：10315-10323
• 全文大小：754K
• 年卷期：0
• ISSN：1944-8252

文摘

We performed density functional theory (DFT) calculations to investigate the synergized O₂ activation and CO oxidation by Ag₈ cluster on TiO₂(101) support. The excellent catalytic activity of the interfacial Ag atoms in O₂ dissociation is ascribed to the positive polarized charges, upshift of Ag d-band center, and assistance of surface Ti_5c atoms. CO oxidation then takes place via a two-step mechanism coupled with O₂ dissociation: (i) CO + O₂ → CO₂ + O and (ii) CO + O → CO₂. The synergistic effect of CO and O₂ activations reduces the oxidation energy barrier (E_a) of reaction (i), especially for the up-layered Ag atoms not in contact with support. It is found that the coadsorbed CO and O₂ on the up-layered Ag atoms form a metal-stable four-center O–O–CO structure motif substantially promoting CO oxidation. On the oxygen defective Ag₈/TiO₂(101) surface, because of the decreased positive charges and the down-shift of d-band centers in Ag, the metal cluster exhibits low O₂ adsorption and activation abilities. Although the dissociation of O₂ is facilitated by the TiO₂(101) defect sites, the dissociated O atoms would cover the defects so strongly that further CO oxidation would be prohibited unless much extra energy is introduced to recreate oxygen defects.