Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 84: Poster Focus Session: Structure and Chemistry of Metal-Oxide Surfaces

O 84.3: Poster

Wednesday, March 14, 2018, 18:15–20:30, Poster A

Electronic and reactive properties of alloyed Au_xPd_y nanoparticles on TiO₂ supports — •Xiaojuan Yu, Alexei Nefedov, Christof Wöll, and Yuemin Wang — Institute of Functional Interfaces, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany.

PdAu bimetallic catalysts have been shown to display enhanced catalytic activities and selectivities compared with their monometallic counterparts in a variety of reactions. However, the nature of the improved catalytic performance of alloyed PdAu nanoparticles (NPs) is still under debate. Here we present the results of a thorough study on various monometallic and bimetallic Au_xPd_y-TiO₂ nanoparticles (x:y = 1:0, 7:3, 1:1, 3:7, 0:1) using primarily ultrahigh vacuum IR spectroscopy (UHV-FTIRS) in conjunction with photoelectron spectroscopy (XPS). The different surface sites of monometallic and bimetallic Au-Pd NPs supported on TiO₂ powders were identified by UHV-FTIRS using CO as a probe molecule. For monometallic Au and Pd NPs, the positively charged Au^δ+ and Pd²⁺ were detected as majority of species, while for bimetallic AuPd NPs, Au⁰, atop Pd⁰ and bridge Pd⁰become the dominating species. The strong electronic interaction between Au and Pd in the alloyed AuPd NPs was demonstrated based on the XPS results and the frequency shift of the corresponding CO bands. The catalysis experiments revealed that the Au₃Pd₇-TiO₂ sample exhibits the highest activity for CO oxidation. This was attributed to the activation of molecular oxygen at the enriched Pd species.