Adsorption of Water Monomer and Clusters on Platinum(111) Terrace and Related Steps and Kinks II. Surface Diffusion

Journal Article · Wed Feb 01 04:00:00 EST 2012 · Surface Science, 606(3-4):233-238

DOI:https://doi.org/10.1016/j.susc.2011.09.024· OSTI ID:1222153

Arnadottir, Liney; Stuve, Eric M.; Jonsson, Hannes

Surface diffusion of water monomer, dimer, and trimer on the (111) terrace, (221) and (322) stepped, and (763) and (854) kinked surfaces of platinum was studied by density functional theory using the PW91 approximation to the energy functional. Monomer diffusion on the terrace is facile, with an activation barrier of 0.20 eV, while dimer and trimer diffusions are restricted due to their high activation barriers of 0.43 and 0.48 eV, respectively. During monomer diffusion on the terrace the O–Pt distance increases by 0.54 Å, about 23% of the initial distance of 2.34 Å. The calculated rate of monomer diffusion hops is in good agreement with the onset temperature of diffusion measurements of Daschbach et al., J. Chem. Phys., 120 (2004) 1516. Alternative monomer diffusion pathways, in which the molecule rolls or flips, were also found. These pathways have diffusion barriers of 0.22 eV. During dimer diffusion on the terrace, the donor molecule rises 0.4 Å at the saddle point, while the acceptor rises by only 0.03 Å. Monomer diffusion up to steps and kinks, with activation barriers of 0.11–0.13 eV, facilitate chain formation on top of step edges. The energy landscape of monomer diffusion from terrace to step to kink sites is downhill with a maximum activation barrier of 0.26 eV. A model for water adsorption is presented inwhichmonomer diffusion leads to concurrent formation of terrace clusters and population of steps/kinks, the latter consistent with the STMmeasurements ofMorgenstern et al., Phys. Rev. Lett., 77 (1996) 703.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1222153
• Journal Information: Surface Science, 606(3-4):233-238, Journal Name: Surface Science, 606(3-4):233-238
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory