Paper GR+NS-MoA8
Stability and Activity of Pt Nanoclusters Supported on Graphene Monolayers on Ru(0001)
Monday, October 18, 2010, 4:20 pm, Room Brazos
| Session: |
Graphene: Chemical Reactions |
| Presenter: |
O. Alves, Ulm University, Germany |
| Authors: |
O. Alves, Ulm University, Germany
C. Lorenz, Ulm University, Germany
H.E. Hoster, Ulm University, Germany
R.J. Behm, Ulm University, Germany
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| Correspondent: |
Click to Email |
Being an atomically thin half-metal and exhibiting moiré-type nm-scale superstructure, graphene monolayers supported on metal single crystals [1-3] can serve as a template for the growth of ordered arrays of nanosized metallic (electro-)catalyst particles. These particles, which are fabricated by simple metal vapour deposition in ultrahigh vacuum [4-6] and comprise monodispersed Pt clusters seeded on the grahene monolayer on Ru(0001), were found to nucleate preferentially at a unique region in the Moiré unit cell and displayed heights of 1-5 atomic layers and lateral diameters within the range 1-4 nm. The size selectivity of the Pt nanoclusters, jointly with their self-assembled array, assign them as interest and promising system for (electro-)catalytic model studies.
We will report on the activity and stability either of a single graphene monolayer or of the Pt clusters. The graphene layers and the cluster arrays are prepared in ultrahigh vacuum, whilst the potential-dependent reaction studies are measured in a wall-jet type flow cell sited in an electrochemical pre-chamber attached to the main UHV system. Cluster arrays with different total Pt coverages and cluster size distributions were tested as electrodes for elementary reactions as hydrogen evolution/oxidation, CO oxidation, or O2 reduction. According to STM analyses before and after the electrochemical tests, we discuss in how far the stabilities of clusters of various sizes can be rationalized in terms of reaction conditions and applied potentials. The general electrochemical behaviour of the Pt cluster arrays will be discussed in comparison to bulk Pt. As a main (electro-)catalytic result, we find a surprisingly high activity for hydrogen evolution.
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[3] Coraux et al., Nano Lett. 8, 565 (2008).
[4] N’Diaye et al., New J. Phys. 11, 103045 (2009).
[5] Yi Pan et al., Appl. Phys. Lett. 95, 093106 (2009).
[6] K. Donner and P. Jakob, J. Chem. Phys. 131 164701 (2009).