Carbon incorporation during ethene oxidation on Pd(111) studied by in situ X-ray photoelectron spectroscopy at 2×10−3 mbar2×10−3 mbar

Gabasch, Harald; Kleimenov, Evgueni; Teschner, Detre; Zafeiratos, Spyridon; Hävecker, Michael; Knop‐Gericke, Axel; Schlögl, Robert; Zemlyanov, Dimitry; Aszalós-Kiss, Balázs; Hayek, K.

doi:10.1016/j.jcat.2006.06.022

Cited by 42 publications

(23 citation statements)

References 45 publications

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“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 46 Third, C could diffuse into the Pd bulk, forming a PdC x phase. Teschner et al 47 and Gabasch et al 48 have assigned Pd 3d 5/2 peaks at 335.7 and 335.34 eV, respectively, to a PdC x phase. Based on our previous in-situ XPS investigation, 18 alloying between palladium and aluminum caused the high BE shift.…”

Section: Experiments Were Performed At the Birck Nanotechnology Centementioning

confidence: 99%

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

et al. 2015

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The behavior of trimethylaluminium (TMA) was investigated on the surfaces of Pt(111) andPd(111) single crystals. TMA was found to dissociatively adsorb on both surfaces between 300 -473 K. Surfaces species observed by high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS) after TMA adsorption at 300 K included Al-CH 3 and CH x,ads (x = 1, 2, or 3) on Pt(111), and ethylidyne (CCH 3 ), CH x,ads (x = 1, 2, or 3), and metallic Al on Pd(111). Density functional theory (DFT) calculations predicted methylaluminum (MA, Al-CH 3 ) to be the most kinetically favorable TMA decomposition product on (111) terraces of both surfaces, however, HREELS signatures for Al-CH 3 were detected only on Pt(111), whereas ethylidyne was observed on Pd(111). XPS demonstrated higher amount of carbonaceous species on Pt(111) than on Pd (111) DFT calculations showed that further dissociation of MA to metallic aluminum and methyl groups to be more kinetically favorable on step sites of both metals. In our proposed reaction mechanism, MA migrates to and dissociates at Pd(111) steps at 300 K forming adsorbed methyl groups and metallic Al. Some methyl groups dehydrogenate and recombine forming ethylidyne. Metallic Al or ejected Pd atoms from steps diffuse across Pd(111) terraces until coalescing into irregularly shaped islands on terraces or steps, as observed by scanning tunneling microscopy (STM). Upon heating above 300 K, the Pd-Al alloy diffuses into the Pd bulk. On Pt(111), a high coverage of carboncontaining species following TMA adsorption at 300 K prevented MA diffusion and dissociation at steps, as evidenced by isolated clusters of MA in STM images. Heating above 300 K resulted in MA dissociation, but no Pt-Al alloy formation was observed. We conclude that the differing abilities of Pd and Pt to hydrogenate carbonaceous species plays a key role in MA dissociation and alloy formation, and, therefore, the adsorption and dissociation chemistry of TMA depends on properties of the metal substrate surface and determines thin film morphology and composition.

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Section: Experiments Were Performed At the Birck Nanotechnology Centementioning

confidence: 99%

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

et al. 2015

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“…In terms of the MSR reaction on PdÀZnO catalysts, one hypothesis that is commonly applied to PdÀZn intermetallic phases that are formed after reduction is based on the idea that the electronic structure of a single metal, such as copper, can be "simulated" by the combination of two or more other metals. [4,20] Besides metallic dopants, dissolved light elements also lead, for example, to PdÀC and PdÀH phases, which can induce substantial changes in selectivity and activity [21,22] by inducing electronic alterations.…”

Section: And Comentioning

confidence: 99%

From Oxide‐Supported Palladium to Intermetallic Palladium Phases: Consequences for Methanol Steam Reforming

et al. 2013

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This Minireview summarizes the fundamental results of a comparative inverse-model versus real-model catalyst approach toward methanol steam reforming (MSR) on the highly CO₂-selective H₂-reduced states of supported Pd/ZnO, Pd/Ga₂O3, and Pd/In₂O3 catalysts. Our model approach was extended to the related Pd/GeO₂ and Pd/SnO₂ systems, which showed previously unknown MSR performance. This approach allowed us to determine salient CO₂-selectivity-guiding structural and electronic effects on the molecular level, to establish a knowledge-based approach for the optimization of CO₂ selectivity. Regarding the inverse-model catalysts, in situ X-ray photoelectron spectroscopy (in situ XPS) studies on near-surface intermetallic PdZn, PdGa, and PdIn phases (NSIP), as well as bulk Pd₂Ga, under realistic MSR conditions were performed alongside catalytic testing. To highlight the importance of a specifically prepared bulk intermetallic[BOND]oxide interface, unsupported bulk intermetallic compounds of Pd_xGa_y were chosen as additional MSR model compounds, which allowed us to clearly deduce, for example, the water-activating role of the special Pd₂Ga-β-Ga₂O₃ intermetallic[BOND]oxide interaction. The inverse-model studies were complemented by their related “real-model” experiments. Structure–activity and structure–selectivity correlations were performed on epitaxially ordered PdZn, Pd₅Ga₂, PdIn, Pd₃Snv, and Pd₂Ge nanoparticles that were embedded in thin crystalline films of their respective oxides. The reductively activated “thin-film model catalysts” that were prepared by sequential Pd and oxide deposition onto NaCl(001) exhibited the required large bimetal[BOND]oxide interface and the highly epitaxial ordering that was required for (HR)TEM studies and for identification of the structural and catalytic (bi)metal[BOND]support interactions. To fully understand the bimetal[BOND]support interactions in the supported systems, our studies were extended to the MeOH- and formaldehyde-reforming properties of the clean supporting oxides. From a direct comparison of the “isolated” MSR performance of the purely bimetallic surfaces to that of the “isolated” oxide surfaces and of the “bimetal[BOND]oxide contact” systems, a pronounced “bimetal[BOND]oxide synergy” toward optimum CO2 activity/selectivity was most evident. Moreover, the system-specific mechanisms that led to undesired CO formation and to spoiling of the CO2 selectivity could be extracted

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“…[6] and Refs therein). On the other hand, partial oxidation of ethylene requires a reduced, carbon-doped and oxygen-depleted surface; moreover, formation of a "dissolved carbon phase" is needed for enhanced selectivity towards C1 oxygenates and CO rather than CO 2 [7]. The basic conclusion is that the chemical state of palladium determines the pathway of a chemical reaction and, therefore, the mechanism of palladium oxidation is crucially important for understanding oxidative catalysis by palladium.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Palladium Oxidation in the mbar Pressure Range: Ambient Pressure XPS Study

et al. 2013

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Palladium oxidation was studied by ambient-pressure X-ray photoelectron spectroscopy in the mbar pressure range on the Pd(111) and Pd(110) surfaces. The oxidation kinetics on both surfaces show an induction period when the oxidation rate was low at the beginning and then accelerated. The slow initial oxidation is governed by (a) the rate of nucleus formation, and (b) the rate of oxide nucleus growth. Depth profiling varying photon energy/kinetic photoelectron energy pointed to a 3D oxidation. It is remarkable that the oxidation of Pd(110) proceeds at ~100 K lower temperatures than on Pd(111). We suggest that at the high temperature required on Pd(111) nucleation is thermodynamically controlled, and therefore, the nucleation rate decreases with temperature. On Pd(110), nucleation is predominantly kinetically controlled and thus the oxidation rate increases with temperature

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Carbon incorporation during ethene oxidation on Pd(111) studied by in situ X-ray photoelectron spectroscopy at 2×10−3 mbar2×10−3 mbar

Cited by 42 publications

References 45 publications

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

From Oxide‐Supported Palladium to Intermetallic Palladium Phases: Consequences for Methanol Steam Reforming

Kinetics of Palladium Oxidation in the mbar Pressure Range: Ambient Pressure XPS Study

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