The Adsorption of Urea on Polycrystalline Gold Electrodes
The adsorption of urea on Au polycrystalline electrodes was investigated using infrared spectroscopy, surface-enhanced infrared absorption (SEIRA) spectroscopy, electrochemistry, and spectroelectrochemistry. Electrochemical investigation indicates urea adsorption on a polycrystalline Au electrode at neutral pH as long as the surface is not oxidized. Partial urea desorption occurs at 0.5 V vs Ag/AgCl and above 0.8 V vs Ag/AgCl Au oxidation occurs, desorbing the remaining urea. Adsorption modes of urea were studied using SEIRA spectroscopy. Urea can adsorb in one of three configurations; through both nitrogen atoms (I), through a single nitrogen atom (II), or through the oxygen atom (III). In H2O, adsorption occurs through both nitrogen atoms (I) and through a single nitrogen atom (II). For experiments in D2O adsorption occurs through both nitrogen atoms (II) and through the oxygen atom (III). The behavior of these adsorbates as a function of potential was studied using spectroelectrochemsitry, where an electrochemical cell with a Au coated IR window at the base is mounted on a benchtop spectrometer and the adsorbates at the surface are investigated as the applied potential is varied. In H2O, at potentials of 0.9 V all of II has desorbed while some of I remains. In D2O experiments, at potentials of 0.9 V all of III has desorbed while some of I remains. Adsorption studies of various possible breakdown products of urea indicates that no known product is being formed.
Urea, SEIRAS, Gold, Infrared Spectroscopy, Adsorption
Master of Science (M.Sc.)