Orientation change of adsorbed pyrazine on roughened rhodium electrodes as probed by surface-enhanced Raman spectroscopy

A surface-enhanced Raman spectroscopic (SERS) study of pyrazine adsorbed on roughened Rh electrodes was performed. Potential and concentration effects on the adsorption behavior of pyrazine were investigated. The SER spectra display four pairs of overlapping bands with the relative intensity of each pair being highly potential dependent, which has not been observed on other metals. The orientation change of the adsorbed pyrazine from the end-on to N/pi bonded edge-on configuration is proposed to account for this potential dependent relative intensity change. This hypothesis is further supported by the SERS results obtained at different pyrazine concentrations. In conjunction with the orientation effect, the interaction of Rh with hydrogen and oxygen generated at different potentials has a great influence on the adsorption configuration of pyrazine.