The adsorption of benzylamine on a polycrystalline gold electrode: A combined spectroelectrochemical study

The adsorption of benzylamine on a polycrystalline gold electrode from aqueous solutions of KClO4 and HClO4 has been studied using differential capacitance measurements (tensammetry) and in situ surface enhanced Raman scattering (SERS). Differences in adsorption parameters of benzylamine adsorbed from neutral solutions at theta < 0.3 and theta > 0.7 can be explained on the basis of the reorientation of adsorbate molecules. Values of the free enthalpy of adsorption Delta G(ad)(0) = -40.0 kJ.mol(-1) and the interaction coefficient a = -1 at theta < 0.3 and Delta G(ad)(0) = -24.3 kJ.mol(-1) with a = 0.55 at theta > 0.7 were obtained. SERS results indicate an edge-on adsorption of benzylamine from KClO4 solution, with a small contribution from molecules adsorbed flat on the gold surface. For benzylamine adsorbed on gold from acidic solution an end-on orientation of molecules with an interaction via the amino group is concluded.