Adsorption of Oxygen on a Ag-Pd alloy surface

The interaction of oxygen with Ag_90.37 Pd_9.63 alloy has been studied by means of XPS. TDS and work function measurements. XPS and TDS results indicate that two kinds of the atomic adsorption states of oxygen exist on the surface of Ag-Pd alloy. One is similar to that on pure silver, its O_1s transition at 530.4 eV, corresponding the peak temperature of desorption around 600K, the desorption activation energy is 142 kJ / mole; the other is related to Pd atom alloyed with Ag, its O_1s peak at 531.8 eV. The adsorbed atomic oxygen increases the surface work function, which is due to the transfer of electron from metal to adsorbate, forming the O_ads^-δ species. For the saturated surface of Ag-Pd alloy the diploe moment per absorbed oxygen is 0.28 Debye. From these data it may be concluded that the Pd atoms in the surface didn’t only act as a diluent, also enhanced surface metal-oxygen bonding by metal-metal bond electron interaction.