Analysis of surface coverage of benzotriazole and 6-tolyltriazole mixtures on copper electrodes from surface-enhanced Raman spectra

The least-squares method has been used to analyze surface-enhanced Raman spectra of benzotriazole (BTA) and 6-tolyltriazole (6-TTA) mixtures on Cu electrodes. The fractional coverage of these molecules on Cu surfaces is dependent on their absolute solution concentration, and is consistent with an assumed Langmuir adsorption isotherm model. The adsorption equilibrium constant of 6-TTA is found to be about three times that of BTA. This indicates that 6-TTA is more strongly adsorbed on Cu than BTA. The free energy of adsorption for 6-TTA on Cu is 610 cal/mol lower than that for BTA.