In Situ Surface Enhanced Raman Spectroscopy on Electrodes with Platinum and Palladium Nanoparticle Ensembles

In situ Raman spectra have been obtained for different species (CN-, CO, H) adsorbed on nanostructured electrodes prepared by deposition of pure Pt and Pd nanoparticles (around 4 nm in size) on either gold or platinum electrodes in acidic solutions. The surface enhancement factor has been estimated on the basis of cyanide spectra obtained both at the surface and in solution. It attains a value as high as 550, around 3−4 times higher than that reported for roughened Pt electrodes for the same adsorbate. In the case of CO, typical bands for the stretching of the Pt/Pd−C and C−O bonds have been observed for low acquisition times (ca. 1 s), evidencing that pure Pt and Pd nanoparticles sustain significant surface enhancement effects. The spectra show mainly atop CO coordination for Pt nanoparticles whereas both linear and bridge CO are detected for Pd nanoparticles. The potential advantages of the nanoparticle-on-electrode approach in Raman spectroelectrochemical studies are highlighted.