SURFACE RAMAN-SPECTRA OF METHANOL DISSOCI ATIVELY ADSORBED AT ROUGHENED PLATINUM-ELECTRODES

For the first time, we have obtained surface Raman spectra of dissocia tive adsorption of methanol at bare Pt electrodes of different surface roughness factors from 60 to 200 by using a confocal Raman microscope and a specific surface roughening procedure. Two bands at around 1 83 0 cm(-1) and 2 040 cm(-1) respectively have been assigned to the CO st reching vibration of the dissociatively adsorbed CO as the poison inte rmediate on the surface. In the low frequency region, the two correlat ed bands at ca 413 cm(-1) and 494 cm(-1) respectively provide a clear vibrational information that there exist the linear bonded Pt-CO and b ridge bonded [GRAPHICS] On the Pt electrode with mild roughness, the R aman signal of CO disappeared at -0.4 V, whereas it was still observab le on the Pt electrode with high roughness. This reveals that the CO-s ubstrate interaction is stronger for the platinum with the higher surf ace roughness, at least partly due to the supercluster interaction of the roughened electrode. In addition, the highly rough surface may be favorable to the formation of island CO, thus enhance the interaction between molecules. It has been shown that surface Raman spectroscopy h as two advantages: first, it provides a uniquely sensitive probe for o btaining surface-adsorbate vibration information in the low frequency region which is typically not accessible to IR spectroscopy. Second, i t can be applied to the study of highly roughened electrodes that are common for practical use. With its notable improvements in detection s ensitivity and functions, Raman spectroscopy will probably become a po werful tool to in-situ study electrocatalysis of practical importance.