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Abstract:
We studied the adsorption of oxygen on Pd(110) in the temperature range from 100 to 600 K. The experimental apparatus used a video LEED system to monitor changes in surface crystallography and two mass spectrometers to study adsorption, desorption and reaction with CO. The sticking coefficient for dissociative oxygen adsorption is 0.86 ± 0.03 at T > 160 K. For T < 160 K molecular oxygen adsorption was observed. Atomic oxygen coverage measurements were performed by reaction of the oxygen with CO to form CO2. Up to a coverage of θ ≈ 0.23, we observed a LEED pattern previously identified as a (1 × 3) overlayer. However, our data rule out a simple adsorbate overlayer. The changes of the reciprocal lattice positions of the "13" spots as a function of oxygen coverage suggest an incommensurate structure with respect to the Pd(110) bulk periodicity. At θ > 0.23 a commensurate c(2 × 4) phase is formed and saturates at θ ≈ 0.48.
