AVS 63rd International Symposium & Exhibition
    Fundamental Discoveries in Heterogeneous Catalysis Focus Topic Wednesday Sessions
       Session HC+SS-WeM

Invited Paper HC+SS-WeM10
Fundamental Studies of the Water-gas Shift and CO2 Hydrogenation on Metal/oxide Catalysts: From Model Systems to Powders

Wednesday, November 9, 2016, 11:00 am, Room 103A

Session: Bridging Gaps in Heterogeneously-catalyzed Reactions
Presenter: Jose Rodriguez, Brookhaven National Laboratory
Correspondent: Click to Email
In this talk, it will be shown how a series of in-situ techniques {X-ray diffraction (XRD), pair-distribution-function analysis (PDF), X-ray absorption spectroscopy (XAS), environmental scanning tunneling microscopy (ESTM), infrared spectroscopy (IR), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)} can be combined to perform detailed studies of the structural, electronic and chemical properties of metal/oxide catalysts used for the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O → H2 + CO2) and the hydrogenation of CO2 to methanol (MS, CO2 + 3H2 → CH3OH + H2O). Under reaction conditions most WGS and MS catalysts undergo chemical transformations that drastically modify their composition with respect to that obtained during the synthesis process. The active phase of catalysts which combine Cu, Au or Pt with oxides such as ZnO, CeO2, TiO2, CeOx/TiO2 and Fe2O3 essentially involves nanoparticles of the reduced noble metals. The oxide support undergoes partial reduction and is not a simple spectator, facilitating the dissociation of water, or the adsorption of CO2, and in some cases modifying the chemical properties of the supported metal. Therefore, to optimize the performance of these catalysts one must take into consideration the properties of the metal-oxide interface. IR and AP-XPS have been used to study the reaction mechanism for the WGS and MS on the metal/oxide catalysts. Data of IR spectroscopy indicate that formate species are not necessarily involved in the main reaction path for these reactions on Cu-, Au- and Pt-based catalysts. Thus, a pure redox mechanism or associative mechanisms that involve either carbonate-like (CO3, HCO3) or carboxyl (HOCO) species should be considered. In the last two decades, there have been tremendous advances in our ability to study catalytic materials under reaction conditions and we are moving towards the major goal of fully understanding how the active sites for the production of hydrogen through the WGS or the hydrogenation of CO2 to methanol actually work.