Initial potential effect on the dissociative adsorption of methanol on a roughened platinum electrode in acidic solution

In situ Raman spectroscopic and voltammetric studies indicate that dissociative adsorption of methanol on the rough platinum electrode occurs in the hydrogen ad/desorption potential range, and the dissociative extent depends on the initial potential of the electrode before contacting methanol, in addition to the contacting time. As the dissociative product, carbon monoxide competes the site of strongly bound hydrogen preferentially, and shifts the ad/desorption potentials of weakly bound hydrogen towards more positive ones gradually with the increase of CO coverage. Whereas, formaldehyde dissociates more easily by far and completely suppresses H-adsorption. The confocal Raman spectroscopy developed on transition metals shows some intriguing advantages in investigating electrocatalytic oxidation of small organic molecules

Surface Raman spectroscopic investigation of pyridine adsorption at platinum electrodes - effects of potential and electrolyte

Surface enhanced Raman spectra of pyridine (Py) at Pt electrodes have been investigated as a function of potential and supporting electrolyte. The results show a large difference from those reported for coinage metal electrodes of Ag, Au and Cu, emphasising the effective involvement of chemical enhancement on Pt surfaces. At very negative (or positive) potentials, Raman spectra show the competitive coadsorption of hydrogen (or oxygen-containing species) with Py, and in acidic solutions, PyH+ ions prefer to dissociate into Py adsorbed on Pt surfaces even in the presence of chloride ions. The differences in the surface bonding strength for Py on Pt and coinage metal electrodes are explained in terms of the different electronic configurations of the metals

Surface Raman spectroscopy as a versatile technique to study methanol oxidation on rough Pt electrodes

The emphasis in the present study was placed on developing Raman spectroscopy into a versatile technique, which offers intriguing opportunities for investigating electrocatalytic reaction. Through the in-situ Raman spectroscopic study, with a confocal Raman microscope, on the methanol electrooxidation on platinum electrodes with various surface roughness, it has shown the advantage in obtaining the informative spectra during the surface reaction with high faradaic current. This is hard to be performed by the other spectroscopic methods that have to use the thin-layer cell. The ability to obtain both the low frequency and the high frequency vibrations of Pt-C and C=O bands allows the assignment of surface species unambiguously. The ease of studying the surface bonding, investigating highly roughened surfaces with dark color and using high concentration electrolyte may provide a way to bridge the gap between the systems of fundamental research and practical applications. The results reveal the surface roughness effect on the electrooxidation process and provide clear evidence for the parallel oxidation mechanism. (C) 2000 Elsevier Science Ltd. All rights reserved

Investigation of surface-enhanced Raman scattering from platinum electrodes using a confocal Raman microscope: dependence of surface roughening pretreatment

In order to establish an appropriate surface roughening procedure for obtaining high-quality surface Raman spectra from Pt electrodes, various roughening conditions for the SERS from the adsorbed pyridine, thiocynate and hydrogen are assessed in terms of the corresponding surface Raman intensities, enhancement factors and surface homogeneity. The repetitive square-wave oxidation reduction cycle (SWORC) triangular-wave ORC (TWORC) and platinization have been performed in the present study. The enhancement factor (G) is calculated based on the confocal feature of a confocal microprobe Raman system, showing one to two orders of amplification of Raman signal for adsorbed pyridine on roughened Pt surfaces. The involvement of charge transfer (CT) enhancement is inferred from the SERS intensity-potential profiles that are dependent on excitation lines. In general, the Pt surfaces with different roughness factors (R) can be divided into three categories: (1) the mildly roughened surface with R of 20-30 seems more adequate for the study of SERS mechnism including calculation of G. (2) the moderately roughened surface with R ranging from 20 to 100, providing homogeneous morphologies: is suitable for investigating surface adsorption and reactions; (3) the highly roughened surface with R ranging From 100 to 300, with non-uniform morphologies, could only be used for investigating species having small Raman cross-sections such as hydrogen adsorption. (C) 1998 Elsevier Science B.V. All rights reserved