Analysis of the redox reaction of 9,10phenanthrenequinone on a gold electrode surface by cyclic voltammetry and time-resolved Fourier transform surface-enhanced Raman scattering spectroscopy

The adsorption behavior of 9,10-phenanthrenequione (PQ) onto a gold electrode surface and its surface-confined electrochemical reaction was analyzed by cyclic voltammetry (CV) and surface-enhanced Raman scattering (SERS) spectroscopy. Although PQ could adsorb onto gold and obeyed Langmuir isotherm behavior similarly to the case of graphite electrodes, the adsorptivity of PQ onto a gold surface was much weaker than that on to a graphite surface. In contrast to adsorption of PQ on a graphite electrode where pi-interaction between phenanthrene ring and the electrode surface plays an important role, SERS measurements indicated that the interaction between PQ and the gold surface was caused by a carbonyl oxygen atom of PQ. The surface-confined redox reaction was analyzed in situ by timeresolved (TR) FT-SERS, and it was found that the amount of radical intermediates accumulated on a gold electrode was negligibly small compared to products during 50ms measurements after the potential was stepped-up. The standard electrochemical rate constant (k0) was evaluated from TR SERS spectra, and was found to be 0.08s^-1 for PQ.