title: In situ imaging of Cu2O under reducing conditions: formation of metallic fronts by mass transfer.
abstract: Active catalytic sites have traditionally been analyzed based on static representations of surface structures and characterization of materials before or after reactions. We show here by a combination of in situ microscopy and spectroscopy techniques that, in the presence of reactants, an oxide catalyst's chemical state and morphology are dynamically modified. The reduction of Cu2O films is studied under ambient pressures (AP) of CO. The use of complementary techniques allows us to identify intermediate surface oxide phases and determine how reaction fronts propagate across the surface by massive mass transfer of Cu atoms released during the reduction of the oxide phase in the presence of CO. High resolution in situ imaging by AP scanning tunneling microscopy (AP-STM) shows that the reduction of the oxide films is initiated at defects both on step edges and the center of oxide terraces.
authors.affiliation: Chemistry Department and ‡Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Ashleigh E
authors.initials: AE
authors.lastname: Baber
authors.forename: Fang
authors.initials: F
authors.lastname: Xu
authors.forename: Filip
authors.initials: F
authors.lastname: Dvorak
authors.forename: Kumudu
authors.initials: K
authors.lastname: Mudiyanselage
authors.forename: Markus
authors.initials: M
authors.lastname: Soldemo
authors.forename: Jonas
authors.initials: J
authors.lastname: Weissenrieder
authors.forename: Sanjaya D
authors.initials: SD
authors.lastname: Senanayake
authors.forename: Jerzy T
authors.initials: JT
authors.lastname: Sadowski
authors.forename: José A
authors.initials: JA
authors.lastname: Rodriguez
authors.forename: Vladimír
authors.initials: V
authors.lastname: Matolín
authors.forename: Michael G
authors.initials: MG
authors.lastname: White
authors.forename: Darío J
authors.initials: DJ
authors.lastname: Stacchiola