ADSORPTION AND REACTION OF OXYGEN AND DEUTERIUM ON A PD(110) SURFACE, STUDIED BY DELTA-PHI AND TDS

The co-adsorption of oxygen and deuterium at 100 K on a Pd(110) surface has been studied by measurements of the change in work function (Δφ) and by thermal desorption spectroscopy (TDS). When the surface with co-adsorbed species is heated, the adsorbates O and D react to form D2O which desorbs from the surface at T > 200 K. The D2O desorption peaks shift continuously to lower temperatures as the surface D coverage (θD) increases. The maximum production of D2O is estimated to be ∼ 0.26 ML (1 ML = 9.5 × 1014 atoms cm-2), resulting from reaction in a layer containing 0.65 ML D and ∼ 0.3 ML O. The maximum work function increase caused by adsorption of D to saturation onto oxygen precovered Pd(110) decreases almost linearly with ΔφO of the oxygen precovered surface. On a surface with pre-adsorbed D however, the maximum Δφ increase contributed by oxygen adsorption decreases abruptly at ΔφD > 200 mV. This sharp change occurs at θD > 1 ML and is believed to be associated with the development of the reconstructed (1 × 2) phase of D/Pd(110). © 1990.