Atomically Dispersed Pd, Ni, and Pt Species in Ceria-Based Catalysts: Principal Differences in Stability and Reactivity

详细信息    查看全文

• 作者：Armin Neitzel ; Alberto Figueroba ; Yaroslava Lykhach ; Tomáš Skála ; Mykhailo Vorokhta ; Nataliya Tsud ; Sascha Mehl ; Klára Ševčíková ; Kevin C. Prince ; Konstantin M. Neyman ; Vladimír Matolín ; Jörg Libuda
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：May 12, 2016
• 年：2016
• 卷：120
• 期：18
• 页码：9852-9862
• 全文大小：1019K
• 年卷期：0
• ISSN：1932-7455

文摘

We have investigated the stability and the reactivity of atomically dispersed Pt, Pd, and Ni species on nanostructured CeO₂ films by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. All three metals reveal specific similarities associated with the high adsorption energy of atomically dispersed Pt²⁺, Pd²⁺, and Ni²⁺ species that exceeds the corresponding cohesive energies of the bulk metals. The corresponding Pt–CeO₂, Pd–CeO₂, and Ni–CeO₂ model catalysts have been prepared in the form of thin films on CeO₂(111)/Cu(111) substrates and investigated experimentally under ultrahigh vacuum conditions. The atomically dispersed Pt²⁺, Pd²⁺, and Ni²⁺ species were formed exclusively at low concentrations of the corresponding metals. High concentrations resulted in the presence of additional metal oxide phases and emergence of metallic particles. We found that under the employed experimental conditions the Pd–CeO₂ films closely resemble the Pt–CeO₂ system with respect to the redox behavior upon reaction with hydrogen. Unlike Pt–CeO₂, the Pd–CeO₂ system shows a strong tendency to stabilize Pd²⁺ not only at the surface but also in the ceria bulk. In sharp contrast to both Pt–CeO₂ and Pd–CeO₂, the Ni–CeO₂ system does not exhibit the redox functionality required for hydrogen activation due to the remarkably high stability of Ni²⁺ species.