Hydroxyl Formation on Pt(553)

In this paper, the coadsorption of oxygen atoms and water molecules (D2O) on Pt(553) is studied by using heterodyne-detected vibrational sum-frequency generation spectroscopy under ultrahigh vacuum conditions at 145 K. The imaginary parts of the surface nonlinear susceptibility (Im chi(2)) of the hydrogen-bonded O-D stretching region are successfully obtained for submonolayer water coverage on oxygen-decorated step sites. Dissociation of the water molecules occurs that leads to hydroxyl formation at the steps. The O-D stretching bands of the hydroxyl species are identified at 2600-2700 cm-1, which show positive signals in the Im chi(2) spectra. From the sign and the intensity of Im chi(2), the average angle of the OD bond of the hydroxyl is estimated to be similar to 60 degrees from the surface normal. In addition, a negative peak at 2460 cm-1 is observed that is ascribed to D2O coadsorbed with the hydroxyl at the steps. Possible structures of the hydrogen bond network of the water and hydroxyl complex are proposed. It is also shown that the oxygen decoration at the step strongly affects the proton configuration of the water network at the terrace.

Automated summary

In this study, the coadsorption of oxygen atoms and water molecules on Pt(553) was investigated using vibrational sum-frequency generation spectroscopy. The results revealed the formation of hydroxyl species at the steps due to the dissociation of water molecules. The hydrogen bond network of the water and hydroxyl complex was proposed, and the proton configuration of the water network at the terrace was shown to be strongly influenced by oxygen decoration at the step.