Figure 1. Mechanistic Pathway for Alcohol Oxidation over Au Catalysts in Liquid Water.
Important role of the solvent-water interface is outlined in this figure.
| Gold Catalysis |
Gold is known as the noblest of all metals and has therefore traditionally found use in jewelry and as coinage metal. However, about two decades ago, Haruta and coworkers discovered catalytic activity of supported gold nanoparticles for oxidation of hydrogen and carbon monoxide [1]. This finding has stimulated tremendous interest in the field of gold catalysis. It is now well known that the Au nanoparticles are excellent catalysts for the reaction of oxygen-rich substrates such as oxidation of hydrocarbons, sugars and alcohols, reduction of NOx and synthesis of H2O2 [2].
Our research on gold catalysis focuses on understanding the factors responsible for high catalytic activity and stability of the gold nanoparticles supported on different supports (such as carbon, titania, alumina, etc.) for vapor phase and aqueous phase oxidation reactions. Previous work demonstrated the roles of metal particle size and the metal-support interface on the catalytic activity of Au nanoparticles. Additionally, in-situ X-ray absorption spectroscopy indicated that metallic gold is the active state of the element for our reactions of interest. Ongoing research in our lab emphasizes the importance of the metal-solvent interface during reaction mechanism studies over gold catalyzed oxidation reactions.
In particular, we are studying oxidation reactions of carbon monoxide, glycerol, ethanol and hydroxymethylfurfural (HMF). Oxidation of CO is a widely studied model reaction which has many applications, e.g. preferential oxidation of CO from H2 streams for efficient operation of fuel cells, in automobile catalytic converters and for life preservation by removing the toxic CO from submarines, mines and space travel [2]. The reactants glycerol, ethanol and HMF are derived from biorenewable resources and their conversion is important for the success of future biorefineries. Most importantly, hydroxide groups present in liquid water (or fed in the gas phase) participate in the mechanism during oxidation reactions on Au. Ongoing studies utilize isotopically-labeled reagents to probe the mechanism of oxidation on Au catalysts.
Figure 1. Mechanistic Pathway for Alcohol Oxidation over Au Catalysts in Liquid Water.
Important role of the solvent-water interface is outlined in this figure.
1. Haruta, M., N. Yamada, T. Kobayashi, and S. Iijima, J. Catal. 115 (1989) 301.
2. G. C. Bond, C. Louis, D. T. Thompson, Catalysis by gold, vol. 6 of Catalytic Science Series (Imperial, London, 2006).
Recent Publications
W.C. Ketchie, M. Murayama and R.J. Davis, "Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts," Topics in Catal. 44 (2007) 307-317.
W.C. Ketchie, Y.-L. Fang, M.S. Wong, M. Murayama and R.J. Davis, “Influence of Gold Particle Size on the Aqueous-phase Oxidation of Carbon Monoxide and Glycerol,” J. Catal. 250 (2007) 94-101.
W.C. Ketchie, M. Murayama and R.J. Davis, “Selective Oxidation of Glycerol over Carbon-Supported AuPd Catalysts,” J. Catal. 250 (2007) 264-273.
M.C. Kung, R.J. Davis and H.H. Kung, “Understanding Au-Catalyzed Low Temperature CO Oxidation,” J. Phys. Chem. C 111 (2007) 11767-11775.
B.N. Zope and R.J. Davis, “Influence of Reactor Configuration on the Selective Oxidation of Glycerol over Au/TiO2” Topics in Catalysis, 52 (2009) 269-277.
B.N. Zope, D.D. Hibbitts, M. Neurock, and R.J. Davis, “Reactivity of the Gold/Water Interface During Selective Oxidation Catalysis,” Science, 330 (2010) 74-78.
S.E. Davis, L.R. Houk, E.C. Tamargo, A.K. Datye, and R.J. Davis, “Oxidation of 5-Hydroxymethylfurfural over Supported Pt, Pd and Au Catalysts,” Catal. Today 160 (2011) 55-60.
B.N. Zope and R.J. Davis, “Inhibition of Gold and Platinum Catalysts by Reactive Intermediates Produced in the Selective Oxidation of Alcohols in Liquid Water,” Green Chem. 13 (2011) 3484-3491.
S.E. Davis, B.N. Zope and R.J. Davis “On the mechanism of selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over supported Pt and Au catalysts” Green Chem. 14 (2012) 143-147.