The origin of the synergistic catalytic effect between metal catalysts and reducible oxide has been debated for decades. Clarification of this effect, namely the strong metal–support interaction (SMSI), requires an understanding of the geometric and electronic structures of metal–metal oxide interfaces under operando conditions. A bimetallic Pt alloy catalyst is an excellent platform to uncover the contentious role of the metal–metal oxide interface because the alloyed transition metal can coexist with the Pt surface layer in the form of an oxidized species on the bimetal surface during catalytic reactions. In addition, mixed catalysts that is composed of Pt nanoparticles supported on metal oxide supports have been mainly utilized as the model catalysts for elucidation of SMSI effect.<br/>In this talk, I present in-situ observation results of structural modulation on Pt-based bimetal catalysts and mixed catalysts. We utilized PtNi, and PtCo that includes both of single crystal and nanoparticle surfaces as model catalysts. Ambient-pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy measurements under CO oxidation conditions show that the coexistence of Pt and metal oxide leads to the enhancement of catalytic activity, indicating these metal-oxide interfaces provide more efficient reaction path for CO oxidation. As a mixed catalysts, we prepared the model catalysts composed of Pt nanoparticles and the mesoporous cobalt oxide that shows the enhancement of catalytic activity. Combining other in-situ techniques including environmental transmission electron microscopy, hot electron measurement, and in-situ diffuse reflectance FT-IR spectroscopy, we conclude that the interface between Pt nanoparticles and oxide is the key factor that gives rise to SMSI effect. Our results show that the presence of metal-oxide interfaces and the charge transfer through the interface have significant implications in the surface reaction of heterogeneous catalysis.

Elucidating mechanisms of strong metal–support interaction on model catalysts using operando surface techniques

ACS Spring Meeting 2021

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