C–O bond scission on “defect-rich and perfect” Pd(1 1 1)?

To investigate the influence of surface defects on CO adsorption and dissociation, well-annealed and “defect-rich” Pd(1 1 1) 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(1 1 1). 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 H2. A possible relationship between the adsorption geometry and C–O bond scission is discussed.