Abstract
Kinetics of molecular oxygen/Au(001) surface interaction has been studied at high temperature and near atmospheric pressures of O2 gas with in situ X-ray scattering measurements. We find that the hexagonal reconstruction (hex) of Au(001) surface lifts to (1 × 1) in the presence of O2 gas, indicating that the (1 × 1) is more favored when some oxygen atoms present on the surface. The measured lifting rate constant vs temperature is found to be highest at intermediate temperature exhibiting a “volcano”-type behavior. At low temperature, the hex-to-(1 × 1) activation barrier (Eact = 1.3(3) eV) limits the lifting. At high temperature, oxygen adsorption energy (Eads = 1.6(2) eV) limits the lifting. The (1 × 1)-to-hex activation barrier (Ehex = 0.41(14) eV) is also obtained from hex recovery kinetics. The pressure–temperature (PT) surface phase diagram obtained in this study shows three regions: hex at low P and T, (1 × 1) at high P and T, and coexistence of the hex and (1 × 1) at the intermediate P and T.
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