title: Influence of size-induced oxidation state of platinum nanoparticles on selectivity and activity in catalytic methanol oxidation in the gas phase.
abstract: Pt nanoparticles with various sizes of 1, 2, 4, and 6 nm were synthesized and studied as catalysts for gas-phase methanol oxidation reaction toward formaldehyde and carbon dioxide under ambient pressure (10 Torr of methanol, 50 Torr of oxygen, and 710 Torr of helium) at a low temperature of 60 °C. While the 2, 4, and 6 nm nanoparticles exhibited similar catalytic activity and selectivity, the 1 nm nanoparticles showed a significantly higher selectivity toward partial oxidation of methanol to formaldehyde, but a lower total turnover frequency. The observed size effect in catalysis was correlated to the size-dependent structure and oxidation state of the Pt nanoparticles. X-ray photoelectron spectroscopy and infrared vibrational spectroscopy using adsorbed CO as molecular probes revealed that the 1 nm nanoparticles were predominantly oxidized while the 2, 4, and 6 nm nanoparticles were largely metallic. Transmission electron microscopy imaging witnessed the transition from crystalline to quasicrystalline structure as the size of the Pt nanoparticles was reduced to 1 nm. The results highlighted the important impact of size-induced oxidation state of Pt nanoparticles on catalytic selectivity as well as activity in gas-phase methanol oxidation reactions.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Hailiang
authors.initials: H
authors.lastname: Wang
authors.forename: Yihai
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhongwei
authors.initials: Z
authors.lastname: Zhu
authors.forename: Andras
authors.initials: A
authors.lastname: Sapi
authors.forename: Kwangjin
authors.initials: K
authors.lastname: An
authors.forename: Griffin
authors.initials: G
authors.lastname: Kennedy
authors.forename: William D
authors.initials: WD
authors.lastname: Michalak
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Somorjai