AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA3
Wetting on Metal Surfaces at Ambient Conditions: A Photoemission Spectroscopy Study

Tuesday, November 14, 2006, 2:40 pm, Room 2004

Session: Water-Surface Interactions on Metals
Presenter: S. Yamamoto, Stanford Synchrotron Radiation Laboratory
Authors: S. Yamamoto, Stanford Synchrotron Radiation Laboratory
K. Andersson, Stanford Synchrotron Radiation Laboratory
H. Bluhm, Lawrence Berkeley National Laboratory
G. Ketteler, Lawrence Berkeley National Laboratory
D.E. Starr, Lawrence Berkeley National Laboratory
T. Schiros, Stanford Synchrotron Radiation Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
H. Ogasawara, Stanford Synchrotron Radiation Laboratory
A. Nilsson, Stanford Synchrotron Radiation Laboratory
Correspondent: Click to Email
The wetting phenomena at surfaces play a crucial role in chemical, biological and environmental processes, such as heterogeneous catalysis, corrosion and the global cycling of chemical elements. The structure and property of water on surfaces in equilibrium with its vapor at ambient conditions, however, remains poorly understood. Here we have investigated the adsorption of water on Cu(110) and Cu(111) at ambient conditions (T= 0~200 @super o@C, relative humidity< 25 %), using in-situ X-ray photoemission spectroscopy. Cu(110) and (111) surfaces exhibit a remarkable difference in the wettability and water chemistry. On Cu(110), the OH and H@sub 2@O mixed layer is observed at relative humidities below 0.1 % (wetting). In contrast, on Cu(111), neither hydroxyl species nor molecular water are present even at a relative humidity of 25 % (non-wetting). This difference originates from the activation barrier for water dissociation on two Cu surfaces ((111)>(110)). Once the hydroxyl groups are formed on the surface, they act as anchoring sites for water molecules. This is because the hydrogen bond between OH and H@sub 2@O is stronger than that between two water molecules. We will also show that the wettability of surfaces can be controlled by preadsorbed oxygens, which change the dissociation barrier of water.