Bradley University1, Mund-Lagowski Department of Chemistry and Biochemistry, Peoria, IL 61625 University of Southern California2, Department of Chemistry, Los Angeles, CA 90089
Analytical and Physical Chemistry
EVIDENCE OF COOPERATIVE ADSORPTION OF CO AND WATER ON ROUGHENED GOLD SURFACES USING VIBRATIONAL SUM FREQUENCY GENERATION SPECTROSCOPY, Joshua G. Hinman1, Fadel Y. Shalhout2, Sergey Malyk2, Alexander V. Benderskii*2, Bradley University1, Mund-Lagowski Department of Chemistry and Biochemistry, Peoria, IL 61625, University of Southern California2, Department of Chemistry, Los Angeles, CA 90089, alex.benderskii@usc.edu
Titanium oxide-supported gold nanoparticles have sparked much interest for their potential as photocatalytic substrates. Vibrational sum frequency generation (SFG) spectroscopy was used to study the adsorption of CO and water on Au surfaces. CO, a convenient spectroscopic chromophore, is a likely reaction intermediate in the reduction of CO2 with water. For CO2 reduction on Au/TiO2 substrates, it is important to understand how CO binds to the Au surface. Au nanoparticles, polycrystalline Au (111), and roughened Au surfaces were exposed to CO, water, and mixtures of CO and water at room temperature and pressure and the adsorbed species were analyzed based on their vibrational SFG spectra. While no adsorption was observed for polycrystalline Au (111), the Au nanoparticles showed atop CO adsorption, characterized by a peak at 2100 cm-1 after exposure to CO and an additional peak at 1950 cm-1 due to bridged/3-fold hollow site CO after exposure to a gaseous mixture of CO and water. The vibrational SFG spectrum for roughened gold after exposure to CO indicated only the peak at 1950 cm-1 and no peak at 2100 cm-1. CO adsorption to the bridged/3-fold hollow site on roughened Au was enhanced by more than a factor of 3 when water vapor was added to the mixture. Similarly, water adsorption to the roughened Au was enhanced after exposure to a CO and water mixture compared to exposure to water alone. Thus, the bridged/3-fold hollow site CO adsorption site on Au exhibits cooperative adsorption of CO and water.
[Abstract (DOC)]