Adsorption and Coadsorption of Hydrogen and CO on Pd（110）

The adsorption and coadsorption of hydrogen and coadsorption of Pd（110） at 300 K have been investigated with XPS, UPS, LEED and TDS. Increasins of CO exposure induces the progressively β₂ and β₁ states population and a shift of C（1s） binding energy from 285. 3 to 285. 7eV. The chemisorbed hydrogen could be completely displaced by CO and further promoted to penetrate into the bulk to form the dissolved hydrogen, particularly at high CO coverage. Even a Pd （110） surface saturated with CO does not hinder hydrogen to absorb and further to penetrate into the bulk. Although TDS and UPS results suggest a weakly interaction energy between both components on Pd （110）, but the H-CO repulsion forces the H atoms in nearby hollow sites on the surface into subsurface. The coadsorbed CO at high coverage might be favorable to this hydrogen configuration for penetration into the bulk.