Unveiling the mechanism of water partial dissociation on Ru(0001).
We have studied the mechanism of the partial dissociation of water on Ru(0001) by high resolution scanning tunneling microscopy (STM). The thermal evolution of water at submonolayer coverage has been tracked in the 110-145 K temperature range to identify the precursor structures for the partial dissociation. These were found to consist of hexagons arranged in thin stripes aligned along the close packed Ru [21¯1¯0] directions. The partially dissociated phase, on the other hand, contains a mixture of H2O and OH hexagons arranged into wider stripes and rotated by 30° with respect to the intact water stripes. The atomic structure of both types of stripes is determined with the aid of density functional theory and STM simulations, providing insights into the partial dissociation reaction path. The reaction is found to be exothermic by around 0.4 eV and initiating at the edges of the intact water stripes. Hydrogen atoms, from water dissociation or already present at the surface, are found to play an important role in the kinetics of the reactions.
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Physics, University of Erlangen-Nürnberg, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany.
Sabine
S
Maier
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
Ingeborg
I
Stass
Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, 28049 Madrid, Spain.
Jorge I
JI
Cerdá
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.
Miquel
M
Salmeron