NEW RESULTS ON THE ELECTROSORPTION OF UREA AND THIOUREA ON GOLD ELECTRODES

The electrosorption of urea and thiourea on a polycrystalline gold electrode from aqueous solutions of KClO4 and HClO4 has been studied with cyclic voltammetry, tensammetry and Surface Enhanced Raman Spectroscopy SERS. The results show in terms of free energy of adsorption a very strong adsorption in case of thiourea and a less strong adsorption of urea from KClO4 solutions. From acidic solutions no data could be obtained because of the instability of both compounds. SERS results indicate an end-on adsorption of urea from KClO4 solution with the oxygen atom in the coordinating position, from acidic solutions only adsorbed CO2 and adsorbed ammonium ions as products of urea hydrolysis were identified. With thiourea a perpendicular orientation with the sulfur atom in the coordinating position in case of both solutions was found. © 1990.