AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM1
Increased Reactivity of Strained Ni Layers on Ru(0001)

Wednesday, October 4, 2000, 8:20 am, Room 208

Session: Chemical Interactions and Surface Reactivity
Presenter: R.C. Egeberg, Technical University of Denmark
Authors: R.C. Egeberg, Technical University of Denmark
I. Chorkendorff, Technical University of Denmark
Correspondent: Click to Email
Understanding the reactivity of metal surfaces and in particular how to control and manipulate this reactivity is the first step towards improved catalysts. From many surface science studies a detailed knowledge about the structures emerging from metal on metal growth has been gained whilst the link to the overall reactivity of such bimetallic structures has not been equally thoroughly investigated. We here present data showing how to utilize the growth properties of Ni on Ru(0001) to improve the ability of Ni to catalyze the reforming of methane. By growing a pseudomorphical Ni overlayer on Ru(0001) a strained Ni layer is formed with respect to Ni(111). As a result of the change in electronic configuration this procedure results in a more reactive Ni layer as it has been predicted from DFT calculations. In steam reforming catalysis the dissociation of methane is the rate-limiting step and we have therefore focused on the initial sticking of methane on this surface. Thermal experiments at 530 K show that the Ni overlayer is ca. 2 times more reactive than Ru(0001) and ca. 20 times more reactive than Ni(111). As more than 1 monolayer of Ni is deposited the sticking decreases and saturates at the value for Ni(111). The adsorption energy of CO which is used as a probe molecule follows the same trend as the CH@sub 4@ sticking. Supersonic molecular beam experiments support the picture of a lower activation barrier on the strained Ni overlayer. Finally, the ability of the surface to catalyze the partial oxidation of methane is under investigation.