| AVS 58th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology Division | Wednesday Sessions |
| Session NS-WeM |
| Session: | Carbon-Based Nanomaterials |
| Presenter: | Jan Knudsen, Lund University, Sweden |
| Authors: | J. Knudsen, Lund University, Sweden T. Gerber, University of Cologne, Germany E. Graanäs, Lund University, Sweden P.J. Feibelman, Sandia National Laboratories K. Schulte, Lund University, Sweden P. Stratman, University of Cologne, Germany C. Busse, University of Cologne, Germany T. Michely, University of Cologne, Germany J.N. Andersen, Lund University, Sweden |
| Correspondent: | Click to Email |
Model systems of real catalysts consisting of nanoparticles deposited on substrates often have a broad size distribution, making it difficult to link the adsorption properties to the atomic scale structure of the nanoparticles using averaging techniques. Metal nanoparticles grown on a graphene/Ir(111) moiré film, however, show exceptionally well ordered arrays of nanoparticles with an extremely narrow size distribution [1, 2]. Further, it is possible to control the cluster size precisely by adjusting the amount of deposited material, since each moiré unit cell contains one cluster. The narrow size distribution and the easy control of cluster size make metal particles supported by graphene an ideal model system for adsorption studies with averaging techniques.
In this contribution we report on our studies on CO adsorption on such an ideal model system consisting of Pt-clusters grown on a graphene/Ir(111) moiré film using photoemission X-ray spectroscopy (XPS), scanning tunnelling microscopy (STM), and density functional theory (DFT) [3].
For Pt/graphene without CO we observe pinning of the graphene film, as a shoulder at the high binding energy side of the C 1s peak observed for pristine graphene. DFT calculations reveal that this shoulder should be assigned to carbon atoms positioned below and in the vicinity of the Pt clusters, which all are displaced towards the Ir(111) surface.
Upon CO adsorption we observe C 1s and the O 1s peak positions consistent with preferential adsorption in atop sites at the cluster step edges. We also observe that the pinning-induced shoulder in the C 1s spectrum diminish upon CO adsorption, and interpret this as unpinning of the graphene film when CO adsorbs on the clusters step edges. From real time STM movies taken during CO dosing we show that the unpinning of the graphene film leads to coalescences of the Pt clusters, when the clusters are smaller than approximately 10 atoms.
References:
[1] A. T. N'Diaye, S. Bleikamp, P. J. Feibelman, et al., Phys. Rev. Lett. 97 (2006)
[2] A. T. N'Diaye, T. Gerber, C. Busse, et al., New Jour. Phys. 11 (2009)
[3] J. Knudsen, P. J. Feibelman, T. Gerber, E. Grånäs, K. Schulte, P. Stratman, C. Busse, J. N. Andersen, T. Michely (in manuscript)