C-O bond scission on defect-rich and perfect Pd(111)?

To investigate the influence of surface defects on CO adsorption and dissociation, well-annealed and defect-rich Pd(111) were examined by sum frequency generation (SFG) and X-ray photoelectron spectroscopy (XPS) within the pressure range 10(-6)-1 mbar. Ar+ ion sputtering was employed to produce surface defects which exhibited vibrational and photoemission characteristics different from the regular adsorption sites on Pd(111). Even under high-pressure, SFG and XPS indicated that no CO dissociation occurred on both surfaces at 300-400 K. By contrast, C-O bond scission was observed during methanol decomposition producing carbonaceous deposits beside CO and H-2. A possible relationship between the adsorption geometry and C-O bond scission is discussed. (C) 2004 Elsevier B.V. All rights reserved.