The interaction of carbon monoxide with the pure and potassium-promoted Cu(332) surface

Bönicke, Ilva A.; Thieme, F.; Kirstein, W.

doi:10.1016/s0039-6028(97)00482-2

Cited by 8 publications

(2 citation statements)

References 22 publications

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“…This has indeed been previously demonstrated by surface science studies of highly electron donating atoms on metallic surfaces, which additionally identified step-edge surface metal sites as the preferred sitting sites for the decorating atoms. 51,52 The development of higher frequency linear carbonyl bands with an increase in the CO dosage was significantly less marked in this case, suggestive of a lower extent of cobalt surface reconstruction in comparison to catalysts supported on Al 2 O 3 and TiO x @Al 2 O 3 oxides, related to a lower ability of CoRu/ SmO x @AO to dissociate CO at room temperature. For these three catalysts, formation of carbonate species on the oxide supports was evidenced by the development of IR bands in the region 1200−1700 cm −1 at increasing CO coverages (Figure S9 in the Supporting Information).…”

Section: ■ Results and Discussionmentioning

confidence: 77%

Cobalt-Catalyzed Fischer–Tropsch Synthesis: Chemical Nature of the Oxide Support as a Performance Descriptor

et al. 2015

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The effect of the chemical nature of the oxide support on the performance of cobalt Fischer–Tropsch catalysts is investigated. A series of supports is synthesized via monolayer coverage of porous γ-Al2O3 with various oxides representative of a wide range of Lewis acid–base character, as quantified by UV–vis spectroscopy coupled to alizarin adsorption. Incorporation of cobalt (20 wt %) results in model catalysts with identical porosities and similar Co particle sizes (>10 nm), allowing the study of support effects without overlap from diffusional or particle size factors. Under realistic reaction conditions, the initial TOF scales with the acidity of the oxide support, whereas the cobalt time yield and selectivity to industrially relevant C13+ hydrocarbons show a volcano dependence, with a maximum at an intermediate acid–base character. As inferred from in situ CO-FTIR, “selective” blockage of a few cobalt sites, though crucial for CO hydrogenation, by atoms from basic oxides and “unselective” site blockage via decoration of Co nanoparticles (strong metal–support interaction) with acidic, reducible oxides cause a decrease in reaction rate for supports with pronounced alkaline and acidic character, respectively. The extent of secondary isomerization reactions of α-olefin products, of relevance for chain reinsertion processes and product selectivity, also correlates with the support acidity. For a TiO x /Al2O3 as support, a remarkable C13+ productivity exceeding 0.09 molC gCo –1 h–1 is achieved, owing to the combination of optimal activity and selectivity. These results provide a unifying view of the support effects over a considerably broad study space and delineate a blueprint toward advanced Fischer–Tropsch catalysts.

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Section: ■ Results and Discussionmentioning

confidence: 77%

Cobalt-Catalyzed Fischer–Tropsch Synthesis: Chemical Nature of the Oxide Support as a Performance Descriptor

et al. 2015

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“…For coadsorption of H 2 O and sodium on a stepped Ni(111) surface, it was found that preferential adsorption of sodium at step edges led to a reduction in the number of H 2 O molecules which could be considered to be bonded at step edges [14]. For coadsorption of CO with a potassium-promoted Cu(332) surface, it was found that the CO molecules bonded at step sites are the first to be influenced by the coadsorbed potassium [15]. Thus it appears that even in the presence of coadsorbates, the step sites remain more reactive for alkali adsorption.…”

Section: Discussion and Summarymentioning

confidence: 99%

Coadsorption of potassium at step edges on the Ni(100)(2 × 2)p4g-N reconstructed surface

Norris¹,

McGrath²

1999

J. Phys.: Condens. Matter

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4.2 Electron work function of metals and semiconductors

Jakobi¹

2002

Landolt-Börnstein - Group III Condensed Matter

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If an electron beam is directed towards a surface, it gets reflected if its potential is equal to -(E P /e + ∆Φ), the negative value of the primary energy divided by e and corrected for ∆Φ between the surface and the electron emitter (in the widest sense: cathode, electron gun, etc.). Since the surface serves here as the anode in a diode configuration, the name diode method has been chosen. This method was introduced early by P.A. Anderson [35A]. Many details of different experimental set-ups are discussed in [73K2, 79H3]. It was pointed out [85K8] that for carefully chosen conditions and for a patchy surface, i.e., a surface consisting of a composite of smaller areas of different work function, the diode method measures the same arithmetical average of Φ as the Kelvin method (see below). How to use a HREEL spectrometer for the diode method is reported in Ref.[85S3]. Vibrating capacitor method (Kelvin)The vibrating capacitor method is based on the work of Lord Kelvin [1898K] and of Zisman [32Z]. A condensor is formed of the surface to be studied and a reference electrode in front of it which are connected by a ammeter and a variable voltage source. If the capacitance between the plates (sample and reference electrode) is changed, e.g., by changing their distance, a current will flow. By compensating the Ref. p. 4.2-118] 4.2 Electron work function of metals and semiconductors Lando lt-Börnstein New Series III/42A2 4.2-7contact potential difference through the voltage source, the current can be brought to zero. Since Φ of the surface is part of the contact potential, its changes relative to the reference electrode can be measured. A more extended description can be found in Ref. [79H3]. A very versatile instrument of this kind was developed by Besocke [76B]. Data collectionData have been collected for metal as well as semiconductor substrates. In the case of metals only elemental, single-crystalline samples were considered. There are a few exceptions to this general rule. Some metallic alloys are listed in case of single-crystalline samples of well defined (stoichiometric) composition. Some data are also incorporated for evaporated, mostly polycrystalline films of materials for which no single-crystal data are available. For semiconductor substrates, adsorbate-induced workfunction changes consist of two contributions: band-bending and electron-affinity changes. Systems were discarded for which the overall change in work function was small (<0.2 eV) or for which the authors did not report a separation of the two contributions. With respect to the adsorbates, only single-component adsorption layers were considered, i.e., co-adsorbates were omitted. Furthermore, it should be noted that completeness -although intended -could not be achieved. It was learned that work-function data are very often not in the center of a publication. Work-function data even seemed to many authors too marginal to give explicitly reference to them in the title, abstract or key words. Therefore, also computer based research could not guarant...

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The interaction of carbon monoxide with the pure and potassium-promoted Cu(332) surface

Cited by 8 publications

References 22 publications

Cobalt-Catalyzed Fischer–Tropsch Synthesis: Chemical Nature of the Oxide Support as a Performance Descriptor

Cobalt-Catalyzed Fischer–Tropsch Synthesis: Chemical Nature of the Oxide Support as a Performance Descriptor

Coadsorption of potassium at step edges on the Ni(100)(2 × 2)p4g-N reconstructed surface

4.2 Electron work function of metals and semiconductors

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