Mechanistic Study of Methanol Decomposition and Oxidation on Pt(111)

Miller, A. V.; Каичев, В. В.; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.

doi:10.1021/jp3122177

Cited by 81 publications

(66 citation statements)

References 72 publications

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“…These values were calculated using the QUASES-IMFP-TPP2M software [32,33] under assumption that palladium remains the predominant constituent in the near-surface region. Since the core-level spectra were collected at normal emission of photoelectrons, and the electron intensity exponentially decays with the sampling volume, according to the well-known Beer-Lambert formalism, the XPS analysis depth can be estimated as 3 , and therefore these energies correspond to the analysis depths approximately equal to 13,17,22, and 30Å, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The reasons for the decrease or increase in activity of palladium were unraveled by X-ray photoelectron spectroscopy (XPS) and temperatureprogrammed reaction spectroscopy (TPRS). XPS is one of the powerful tools in the catalytic surface science to investigate both the surface composition and the nature of adsorbed species; while TPRS can provide direct information about catalytic properties of samples under study [19][20][21][22]. A Pd(5 5 1) single crystal was used as a model catalyst.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

et al. 2015

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a b s t r a c tThe oxidation of propylene over a Pd(5 5 1) single crystal surface has been studied by X-ray photoelectron spectroscopy (XPS) and temperature-programmed reaction spectroscopy during both heating and cooling in various oxygen/propylene mixtures. In all the experiments, the partial pressure of propylene was approximately 1 × 10 −7 mbar and the partial pressure of oxygen was varied to achieve molar oxygen/propylene ratios of 1, 3, 10, and 100. Under all these conditions, we observed a temperature hysteresis: temperature dependences of the catalyst activity and product distribution were different during heating and cooling. It was shown that the temperature hysteresis was due to concurrent accumulation of carbon and oxygen atoms on the palladium surface. At low temperatures, a high concentration of carbonaceous deposits detected by XPS resulted in a low catalytic activity due to blocking of the palladium surface. Increasing temperature led to full dehydrogenation of the carbonaceous species and dissolution of carbon atoms into subsurface palladium layers. As a result, even under oxygen-rich conditions, the formation of a PdC x phase was detected by XPS at 373 K. This process had no influence on the selectivity in the oxidation of propylene at least under UHV conditions. A shift of selectivity toward CO 2 was found to result from an increase in the oxygen concentration on the palladium surface. The state with a low catalytic activity in the oxidation of propylene was associated with palladium in the metallic state covered by carbon deposits. The high-active state of palladium was associated with palladium in the metallic state with a high concentration of chemisorbed oxygen and a moderate concentration of a surface oxide. Bulk PdO was not detected by XPS under all conditions used.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

et al. 2015

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“…It should be noted that some reactions indeed can proceed via both the LangmuirHinshelwood and the Mars-van Krevelen mechanisms depending on experimental conditions and a catalyst type [65][66][67][68]. For instance, the oxidation of methane over Pt-based catalysts proceeds via the Langmuir-Hinshelwood mechanism, whereas over Pd-based catalysts, the oxidation of methane proceeds via the Mars-van Krevelen mechanism under the same experimental conditions [65].…”

Section: Discussionmentioning

confidence: 99%

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Каичев

Teschner

Saraev

et al. 2016

Journal of Catalysis

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The evolution of self-sustained reaction-rate oscillations in the catalytic oxidation of propane over a nickel foil has been studied in situ using X-ray photoelectron spectroscopy coupled with on line mass spectrometry and gas chromatography. Changes in the effective surface area and in the catalyst morphology under reaction conditions have been examined by scanning electron microscopy and a krypton adsorption technique. It is shown that the regular kinetic oscillations arise under oxygen-lean conditions. CO, CO 2 , H 2 , H 2 O, and propylene are detected as products.The conversion of propane oscillates in a range from 1% to 23%. During the half-periods with high activity, the main reaction pathway is the partial oxidation of propane: selectivity toward CO achieves 98%. In contrast, during the half-periods with low activity, the reaction proceeds through three competitive pathways: the partial oxidation of propane, the total oxidation of propane, and the dehydrogenation of propane to propylene. The driving force for the selfsustained kinetic oscillations is the periodic reoxidation of nickel. According to the Ni2p and O1s core-level spectra measured in situ, the high-active catalyst surface is represented by metallic nickel, whereas during the inactive half-periods the catalyst surface is covered with a thick layer of NiO. The intensity of O1s spectra follows the oscillations of O 2 in the gas phase during the oxidation of propane. It is found that during the induction period before the regular oscillations appear, a rough and porous structure develops because of strong reconstruction of the catalyst surface. The thickness of the reconstructed layer is approximately 10-20 µm. This process is accompanied with at least an 80-fold increase in the effective surface area compared with a clean, non-treated nickel foil, which undoubtedly leads to a drastic increase in the number of active sites. We believe that it is the main reason for the induction period always being  Corresponding author.E-mail address: vvk@catalysis.ru (V.V. Kaichev) 2 observed before the appearance of self-sustained oscillations in the catalytic oxidation of light hydrocarbons over catalysts with a low specific surface area (single crystals, foils, or wires).Moreover, without such reconstruction, the oscillations cannot arise due to low activity of such catalysts.

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“…However, there are several aspects that gather consensus: (1) hydration of the proton exchange membrane (PEM) leads to proton production in the anode and then begins its transportation through the membrane to the cathode; (2) in the cathode another catalyst is used to combine electrons, protons, and oxygen from the air, resulting in water vapor and carbon dioxide production, while methanol reacts in the anode; and (3) experimental data indicate the methoxy radical (CH 3 O) as the first intermediate in the oxidative process [27][28][29][30][31][32][33][34][35][36][37][38][39]. Therefore, the discussion presented in this section will have in account these aspects and will especially consider the corroboration of existence of methoxy as intermediate in experimental and computational data as a strong indication of pertinent mechanism.…”

Section: Experimental Data and Indiciamentioning

confidence: 99%

Ruthenium–Platinum Catalysts and Direct Methanol Fuel Cells (DMFC): A Review of Theoretical and Experimental Breakthroughs

et al. 2017

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Abstract:The increasing miniaturization of devices creates the need for adequate power sources and direct methanol fuel cells (DMFC) are a strong option in the various possibilities under current development. DMFC catalysts are mostly based on platinum, for its outperformance in three key areas (activity, selectivity and stability) within methanol oxidation framework. However, platinum poisoning with products of methanol oxidation led to the use of alloys. Ruthenium-platinum alloys are preferred catalysts active phases for methanol oxidation from an industrial point of view and, indeed, ruthenium itself is a viable catalyst for this reaction. In addition, the route of methanol decomposition is crucial in the goal of producing H 2 from water reaction with methanol. However, the reaction pathway remains elusive and new approaches, namely in computational methods, have been ensued to determine it. This article reviews the various recent theoretical approaches for determining the pathway of methanol decomposition, and systematizes their validation with experimental data, within methodological context.

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Mechanistic Study of Methanol Decomposition and Oxidation on Pt(111)

Cited by 81 publications

References 72 publications

Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

Oxidation of propylene over Pd(5 5 1): Temperature hysteresis induced by carbon deposition and oxygen adsorption

Evolution of self-sustained kinetic oscillations in the catalytic oxidation of propane over a nickel foil

Ruthenium–Platinum Catalysts and Direct Methanol Fuel Cells (DMFC): A Review of Theoretical and Experimental Breakthroughs

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