Surface Enhanced Raman Studies of Processes Occurring On Pt Under Electrochemical Conditions

Tuesday, November 9, 2010: 1:33 PM
151 F Room (Salt Palace Convention Center)
Shannon Klaus, Boon-Siang Yeo and Alexis T. Bell, Department of Chemical Engineering, University of California Berkeley, Berkeley, CA

Electrochemical processes occurring at a roughened Pt electrode in aqueous electrolyte were investigated via in situ surface-enhanced Raman spectroscopy (SERS). Raman spectra were acquired concurrent with cyclic voltammetric scans. A broad band ca. 550 wavenumbers develops under oxidizing conditions, which is ascribed to Pt oxide species containing Pt-OH bonds [1, 2]. This band intensifies with potential increase and subsequently diminishes near the voltammetric region of platinum oxide reduction. Under conditions of oxygen reduction, a band appearing ca. 800 wavenumbers is attributed to adsorbed peroxo- species [3]. During hydrogen overpotential deposition, a band ca. 2088 wavenumbers emerges, corresponding to Pt on-top hydrogen adsorption [4, 5]. All Raman bands exhibit the Stark effect, i.e. a shift to higher frequencies with increased potential. The dynamics of Raman peak formation were probed through potential-step experiments, and Pt surface roughness was characterized via atomic force microscopy (AFM). These results will be discussed in term of the mechanism and kinetics of the electrolysis of water and the electrochemical reduction of oxygen.

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