Browsing by Author "Lyubinetsky, Igor"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Interaction of CO2 with MnOx/Pd(111) reverse model catalytic interfaces
    (Wiley, 2023-07-03) Anıl, Arca; Sadak, Ömer Faruk; Karakurt, Bartu; Koçak, Yusuf; Lyubinetsky, Igor; Özensoy, Emrah
    Understanding the activation of CO2 on the surface of the heterogeneous catalysts comprised of metal/metal oxide interfaces is of critical importance since it is not only a prerequisite for converting CO2 to value-added chemicals but also often, a rate-limiting step. In this context, our current work focuses on the interaction of CO2 with heterogeneous bi-component model catalysts consisting of small MnOx clusters supported on the Pd(111) single crystal surface. These metal oxide-on-metal ‘reverse’ model catalyst architectures were investigated via temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) techniques under ultra-high vacuum (UHV) conditions. Enhancement of CO2 activation was observed upon decreasing the size of MnOx nanoclusters by lowering the preparation temperature of the catalyst down to 85 K. Neither pristine Pd(111) single crystal surface nor thick (multilayer) MnOx overlayers on Pd(111) were not capable of activating CO2, while CO2 activation was detected at sub-monolayer (∼0.7 ML) MnOx coverages on Pd(111), in correlation with the interfacial character of the active sites, involving both MnOx and adjacent Pd atoms. © 2023 The Authors. ChemPhysChem published by Wiley-VCH GmbH.
  • Thumbnail Image
    ItemOpen Access
    Significance of the Mn-Oxidation state in catalytic and noncatalytic promotional effects of MnOx domains in formic acid dehydrogenation on Pd/MnOx interfaces
    (American Chemical Society, 2020) Karakurt, Bartu; Koçak, Yusuf; Lyubinetsky, Igor; Özensoy, Emrah
    The influence of MnOx overlayers/nanoclusters deposited on the Pd(111) single-crystal model catalyst surface on the catalytic dehydrogenation of double-deuterated formic acid (FA, DCOOD) was studied under ultrahigh vacuum conditions via temperature-programmed desorption and X-ray photoelectron spectroscopy techniques. A significant boost in D2 generation was observed in the catalytic FA dehydrogenation on MnOx/Pd(111) as compared to that of a clean Pd(111) model catalyst, demonstrating the cooperative interaction between Pd(111) and MnOx sites. Maximum FA conversion was observed at a submonolayer MnOx surface coverage of 0.25 ML (monolayer) on Pd(111), whereas D2 formation was found to be suppressed when the Pd(111) surface was entirely covered with relatively thick (15 ML) MnOx overlayers. A direct correlation between increasing relative abundance of oxidized Mn surface states (i.e., Mn2+, Mn3+, and Mn4+) and increasing catalytic FA dehydrogenation was observed. Different modes of promotion of FA dehydrogenation via MnOx (i.e., catalytic promotion versus noncatalytic/stoichiometric promotion) were discussed as a function of the differences in the model catalyst preparation and the extent of oxidation of the MnOx overlayer.