AVS 66th International Symposium & Exhibition
    Fundamental Discoveries in Heterogeneous Catalysis Focus Topic Wednesday Sessions
       Session HC+OX+SS-WeA

Invited Paper HC+OX+SS-WeA9
Understanding Metal-Metal and Metal-Support Interactions in Bimetallic Catalysts

Wednesday, October 23, 2019, 5:00 pm, Room A213

Session: Metal-Support Interactions Driving Heterogeneously-Catalyzed Reactions
Presenter: Donna Chen, Univeristy of South Carolina
Authors: D.A. Chen, Univeristy of South Carolina
S. Farzandh, University of South Carolina
D.M. Shakya, University of South Carolina
A.J. Brandt, University of South Carolina
T.D. Maddumapatabandi, University of South Carolina
Correspondent: Click to Email
Bimetallic catalysts are known to exhibit superior properties compared to their individual pure metal components, but in many cases the nature of these improved properties is not well understood. The main goal of this work is to understand how oxidation states, metal-support interactions, and metal-metal interactions in supported bimetallic clusters can be used to control catalytic activity. Specific catalytic reactions investigated are the water gas shift reaction (WGS)on Pt-Re and selective hydrogenation of unsaturated aldehydes on Pt-Sn. Model catalyst surfaces are prepared via vapor-deposition of metal clusters on single-crystal oxide and carbon supports. These surfaces are fully characterized by a variety ultrahigh vacuum (UHV) surface science techniques and their activities are studied in a microreactor (P~ 1 atm) coupled to the UHV chamber. Scanning tunneling microscopy investigations indicate that exclusively bimetallic clusters can be prepared by sequential deposition of metals. For the WGS reaction, the active site is determined to be Pt with subsurface Re, while Re oxide does not play a role. Density functional theory studies show that the presence of subsurface Re decreases the adsorption energy of CO on Pt, thus preventing Pt active sites from being poisoned by CO. WGS activity increases with increasing perimeter for Pt/TiO2 clusters, and the turnover frequency is also lower in the absence of the TiO2 support. For hydrogenation on furfural, the Pt-Sn alloy surface exhibits high selectivity to furfuryl alcohol compared to pure Pt, whereas furan and tetrahydrofuran are the main products on Pt.