AVS 53rd International Symposium
    Surface Science Monday Sessions
       Session SS1-MoA

Paper SS1-MoA4
Design and Stability of Surface Alloys used for Catalytic Conversion of Fossil Fuel to Hydrogen

Monday, November 13, 2006, 3:00 pm, Room 2002

Session: Catalysis for the Hydrogen Economy
Presenter: J. Knudsen, University of Aarhus, Denmark
Authors: J. Knudsen, University of Aarhus, Denmark
R.T. Vang, University of Aarhus, Denmark
J. Schnadt, University of Aarhus, Denmark
E.K. Vestergaard, University of Aarhus, Denmark
T.M. Pedersen, University of Aarhus, Denmark
B. Hammer, University of Aarhus, Denmark
T. An, University of Aarhus, Denmark
I. Stensgaard, University of Aarhus, Denmark
E. Laegsgaard, University of Aarhus, Denmark
A.U. Nilekar, University of Wisconsin-Madison
M. Mavrikakis, University of Wisconsin-Madison
F. Besenbacher, University of Aarhus, Denmark
Correspondent: Click to Email
Clean, cheap and efficient production of high-purity hydrogen is an essential prerequisite for the emerging hydrogen economy. The vast majority of the present hydrogen production comes from catalytic conversion of fossil fuel, which relies heavily on the steam reforming (SR) reaction and the Water-Gas-Shift (WGS) reaction. Supported Ni particles are commercially used as catalysts for the SR reaction, whereas supported Cu particles are currently used for the low-temperature WGS reaction. In this study vacuum deposition of Cu onto Pt(111) at 800 K is used to synthesize stable near-surface alloys (NSA) of Cu/Pt(111). A combination of scanning tunneling microscopy (STM), Core-level photoemission (XPS), Thermal desorption spectroscopy (TDS) and Density functional theory (DFT) is used to characterize the NSAs, and it is found that Cu atoms are stabilized sub-surface, leaving a surface layer free of Cu atoms. Very interestingly, we find that the WGS activity of our new NSA is superior to that of Cu(111), and it is, therefore, very likely that real Cu/Pt near-surface particles could be used as new and improved catalysts for the WGS reaction. Finally, fast high-pressure STM experiments in a high CO pressure are used to examine the stability of this new Cu/Pt(111) near-surface alloy for the WGS reaction, and a previously found Au/Ni(111) surface alloy, which can be used for the SR reaction. From these experiments we conclude that the Cu/Pt(111) NSA remains stable in high pressure of CO in contrast to the Au/Ni(111) surface alloy, which is found to phase separate into small Au clusters on a Ni(111) substrate due to formation of Ni-carbonyls, which remove Ni from the surface.