Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopy

Abstract

Articles you may be interested in Performance and characteristics of a high pressure, high temperature capillary cell with facile construction for operando x-ray absorption spectroscopy Rev. Sci. Instrum. 85, 084105 (2014); 10.1063/1.4893351 Methane dissociative chemisorption and detailed balance on Pt(111): Dynamical constraints and the modest influence of tunneling Electron induced dissociation of trimethyl (methylcyclopentadienyl) platinum (IV): Total cross section as a function of incident electron energy Kinetics of the CO oxidation reaction on Pt(111) studied by in situ high-resolution x-ray photoelectron spectroscopy The concept of liquid organic hydrogen carriers (LOHC) holds the potential for large scale chemical storage of hydrogen at ambient conditions. Herein, we compare the dehydrogenation and decomposition of three alkylated carbazole-based LOHCs, dodecahydro-N-ethylcarbazole (H 12-NEC), dodecahydro-N-propylcarbazole (H 12-NPC), and dodecahydro-N-butylcarbazole (H 12-NBC), on Pt(111) and on Al 2 O 3-supported Pt nanoparticles. We follow the thermal evolution of these systems quantitatively by in situ high-resolution X-ray photoelectron spectroscopy. We show that on Pt(111) the relevant reaction steps are not affected by the different alkyl substituents: for all LOHCs, stepwise dehydrogenation to NEC, NPC, and NBC is followed by cleavage of the C-N bond of the alkyl chain starting at 380-390 K. On Pt/Al 2 O 3 , we discern dealkylation on defect sites already at 350 K, and on ordered, (111)-like facets at 390 K. The dealkylation process at the defects is most pronounced for NEC and least pronounced for NBC. © 2014 AIP Publishing LLC.

Subsurface Oxygen on Pt(111) and Its Reactivity for CO Oxidation

“…Subsequently, the sample temperature was ramped up while recording the partial pressures of m/e = 32 (O 2 ), 28 (CO) and 44 (CO 2 ). In line with previous studies [5,7,42,43], we observe that for a surface saturated with O at 300 K, all CO as well as most of the oxygen react to form CO 2 . However, when the surface is initially oxidized at 500 K, some amount of CO as well as O 2 are left the surface after the same amount of CO 2 have been formed.…”

“…To this end we have carried temperature programmed reaction (TPR) measurements to check how oxygen adsorbed on Pt(111) at various temperatures reacts with carbon monoxide. From previous studies it is known that the 0.25 ML of atomic oxygen on Pt(111) does not react with CO at temperatures below 150 K [5,7]. CO and O co-adsorb in a 1:1 [42,43] ratio and an increase in surface temperature activates the reaction that produces CO 2 .…”

“…The industrial and technological importance is reflected in the efforts by the scientific community to understand the interaction between the platinum surface and gas phase oxygen over the last four decades [1][2][3][4][5][6][7][8][9][10][11]. Although this effort has yielded a wealth of information, we show in this article that even the most intensely studied system, O 2 /Pt(111), can still yield surprising results that affect our view of the catalytic action under realistic conditions.…”

Promotion Effect of Platinum on Gold’s Reactivity: A High-Resolution Photoelectron Spectroscopy Study

“…The main conclusion drawn from these results is that the C feature at higher BE is composed by 3 components at 288.10, 287.11 and 286.43 eV. These components, when compared with data reported in the literature, can be ascribed to C belonging to CO adsorbed on Pt in top and bridge positions (287.11 and 286.43 eV) 36 and on Au (288.10eV) 12,14 , once again suggesting that both Pt and Au sites are active for CO adsorption at room temperature; the same contributions of top and bridge positions 15 predicted by DFT simulations for the Pt/Au(332) system. However, since the surface has a mixed composition due to the interatomic exchange of Au and Pt atoms, we believe that bridge sites could be both homogeneous and heterogeneous; i.e., formed by Pt-Pt or Pt-Au atoms.…”

Reactivity of a gas/metal/metal-oxide three-phase boundary: CO oxidation at the Pt(111)–c(4×2)-2CO/α-PtO2 phase boundary

“…Examples include: (i) exposure of an oxygen pre-covered Pt(1 1 1) surface to CO [14,15], (ii) exposure of a CO precovered Pt(1 1 1) surface to high pressure O 2 [16], and (iii) time-dependent reactivity studies of Pt(1 1 0) under large and small CO/O 2 pressure ratios [2]. In case (i), the surface was found to accommodate two coexisting adsorbate phases, c(4 · 2)-2CO, and p(2 · 2)-(O + CO), in case (ii) vacancies in the saturated CO adsorption phase were found to be necessary during transient reaction conditions, and in case (iii), an oxide phase was shown to be growing during steady state reaction conditions.…”