| AVS 61st International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS+EN-MoA |
| Session: | Metals, Alloys and Oxides: Structure, Reactivity & Catalysis |
| Presenter: | Donna Chen, University of South Carolina |
| Authors: | A.S. Duke, University of South Carolina R.P. Galhenage, University of South Carolina K. Xie, University of South Carolina S.A. Tenney, Brookhaven National Laboratory P. Sutter, Brookhaven National Laboratory D.A. Chen, University of South Carolina |
| Correspondent: | Click to Email |
Methanol oxidation has been investigated on Pt-Re bimetallic surfaces in order to understand how the addition of Re promotes activity on Pt in alcohol reforming and other oxidation reactions. Pt-Re alloy surfaces were prepared by depositing Re on Pt(111) or polycrystalline Pt foils and annealing to 1000 K. Scanning tunneling microscopy studies demonstrate that the deposited Re islands diffuse into the Pt(111) surface upon annealing, and low energy ion scattering studies indicate that the top monolayer consists mainly of Pt. XPS investigations were carried out at the X1A1 beamline at the National Synchrotron Light Source under methanol oxidation conditions of 200 mtorr O2/100 mtorr methanol between 300 and 550 K, and gaseous products were monitored using a mass spectrometer. Methanol oxidation was studied on clean Pt(111), the Pt-Re alloy and Re films grown on Pt before and after surface oxidation at 450 K. The main products on all surfaces were CO2 and H2O with formaldehyde, CO and H2 as minor products. On the unoxidized surfaces, the selectivity toward H2 and CO production increased above 500 K. Deposition of atomic carbon during reaction was suppressed on the Pt-Re alloy surfaces as compared to pure Pt, and the oxidized Pt-Re alloy was found to reach maximum activity at the lowest temperatures. The Re films were unstable under methanol oxidation conditions at temperatures above 450 K due to the sublimation of Re oxides, but the Re in the Pt-Re alloy remained on the surface under the same conditions. Activity studies in a flow reactor coupled to the ultrahigh vacuum chamber showed that methanol oxidation activity increases with surface oxidation; unoxidized Pt and Pt-Re surfaces initially exhibit minimal activity until the surface becomes oxidized under reaction conditions.