In situ UV–vis plasmon resonance spectroscopic assessment of oxygen and hydrogen adsorption location on supported gold catalysts

Abstract Here we report an in situ UV–vis spectroscopy study of O2 and H2 adsorption on small gold nanoparticles supported on SiO2, Al2O3, ZrO2, ZnO, and TiO2 P-25 at high temperature which provides insights into gold adsorption and active sites. In situ gold surface plasmon resonance peak shifts from alternating and consecutive adsorption of O2 to H2 were correlated to relative charge transfer from/to gold via a Drude-Lorentz model considering contributions from free electrons and interband transitions. A novel methodology matching the relative charge transfer (from O2 and H2 adsorption at 398 K and flowing conditions) with Au surface site statistics derived from a truncated octahedron geometric model was used to provide strong in situ experimental and spectroscopic evidence for adsorption of O2 and H2 at the gold-support perimeter, which agrees with prior hypotheses for active site location from reactivity and theoretical studies. The prepared catalysts were also evaluated for CO oxidation at 398 K. The resulting TOFs normalized per different surface site location indicated that conversion rates were not limited by the density of sites at the gold-support perimeter, but primarily by the total gold surface sites, which were also further differentiated by the reducibility of the catalyst support.