title: Dramatically different kinetics and mechanism at solid/liquid and solid/gas interfaces for catalytic isopropanol oxidation over size-controlled platinum nanoparticles.
abstract: We synthesize platinum nanoparticles with controlled average sizes of 2, 4, 6, and 8 nm and use them as model catalysts to study isopropanol oxidation to acetone in both the liquid and gas phases at 60 °C. The reaction at the solid/liquid interface is 2 orders of magnitude slower than that at the solid/gas interface, while catalytic activity increases with the size of platinum nanoparticles for both the liquid-phase and gas-phase reactions. The activation energy of the gas-phase reaction decreases with the platinum nanoparticle size and is in general much higher than that of the liquid-phase reaction which is largely insensitive to the size of catalyst nanoparticles. Water substantially promotes isopropanol oxidation in the liquid phase. However, it inhibits the reaction in the gas phase. The kinetic results suggest different mechanisms between the liquid-phase and gas-phase reactions, correlating well with different orientations of IPA species at the solid/liquid interface vs the solid/gas interface as probed by sum frequency generation vibrational spectroscopy under reaction conditions and simulated by computational calculations.
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.
authors.forename: Hailiang
authors.initials: H
authors.lastname: Wang
authors.forename: Andras
authors.initials: A
authors.lastname: Sapi
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Thompson
authors.forename: Fudong
authors.initials: F
authors.lastname: Liu
authors.forename: Danylo
authors.initials: D
authors.lastname: Zherebetskyy
authors.forename: James M
authors.initials: JM
authors.lastname: Krier
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Carl
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Cai
authors.forename: Lin-Wang
authors.initials: LW
authors.lastname: Wang
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Somorjai