Adsorption of oxygen on Rh(110): a LEED, Auger electron spectroscopy and thermal desorption study

The adsorption of oxygen on the Rh(110) surface has been studied by a variety of techniques. Low-energy electron diffraction shows the following patterns: (2 × 1)p2mg at 1 ML coverage and temperatures between 125 and 300 K; (2 × 2)p2mg at 0.5 ML coverage after heating to above 470 K; c(2 × 8) and complex streaked c(2 × 2n) patterns at coverages above 0.5 after heating to 470 K. These results are in partial agreement with previous work. Models for the first two structures are suggested. In the (2 × 2) structure, the oxygen is found to be much less reactive with CO at room temperature than in the (2 × 1) structure, suggesting that it is subsurface. A metastable (1 × 2) structure was produced from the (2 × 2) by reduction of the oxygen by CO at 450 K, and is interpreted as a surface reconstruction.