Ethene adsorption and dehydrogenation on clean and oxygen precovered Ni(111) studied by high resolution x-ray photoelectron spectroscopy

Lorenz, Michael; Fuhrmann, Thomas; Streber, Regine; Bayer, Andreas; Bebensee, Fabian; Gotterbarm, Karin; Kinne, M.; Tränkenschuh, B.; Zhu, Junfa; Papp, Christian; Denecke, R.; Steinrück, Hans‐Peter

doi:10.1063/1.3456732

Cited by 26 publications

(27 citation statements)

References 38 publications

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“…Because we can fit the spectrum with only a single CH 2 peak, we conclude that coadsorption of hydrogen favors a symmetric adsorption geometry. On Ni(111), a similar change of the C 1s photoemission spectrum of ethene, from two to one peak (asymmetric to symmetric adsorption), was found as a result of coadsorption with O ad . DFT modeling confirms this notion: for 0.11 ML ethene coadsorbed with 0.44 ML H ad , calculations predict an adsorption geometry in which both carbon atoms are equivalent, and with the molecule occupying a close-to atop site.…”

Section: Resultsmentioning

confidence: 55%

Adsorption and Decomposition of Ethene and Propene on Co(0001): The Surface Chemistry of Fischer–Tropsch Chain Growth Intermediates

et al. 2016

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Experiments that provide insight into the elementary reaction steps of C x H y adsorbates are of crucial importance to better understand the chemistry of chain growth in Fischer−Tropsch synthesis (FTS). In the present study we use a combination of experimental and theoretical tools to explore the reactivity of C 2 H x and C 3 H x adsorbates derived from ethene and propene on the close-packed surface of cobalt. Adsorption studies show that both alkenes adsorb with a high sticking coefficient. Surface hydrogen does not affect the sticking coefficient but reduces the adsorption capacity of both ethene and propene by 50% and suppresses decomposition. On the other hand, even subsaturation quantities of CO ad strongly suppress alkene adsorption. Partial alkene dehydrogenation occurs at low surface temperature and predominantly yields acetylene and propyne. Ethylidyne and propylidyne can be formed as well, but only when the adsorbate coverage is high. Translated to FTS, the stable, hydrogenlean adsorbates such as alkynes and alkylidynes will have long residence times on the surface and are therefore feasible intermediates for chain growth. The comparatively lower desorption barrier for propene relative to ethene can to a large extent be attributed to the higher stability of the molecule in the gas phase, where hyperconjugation of the double bond with σ bonds in the adjacent methyl group provides additional stability to propene. The higher desorption barrier for ethene can potentially contribute to the anomalously low C 2 H x production rate that is typically observed in cobalt-catalyzed FTS.

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Section: Resultsmentioning

confidence: 55%

Adsorption and Decomposition of Ethene and Propene on Co(0001): The Surface Chemistry of Fischer–Tropsch Chain Growth Intermediates

et al. 2016

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“…Figure 1a shows high-resolution C1s spectra of the different surface intermediates that form during heating of an ethylenesaturated surface in vacuum, previously discussed in detail elsewhere 21 . The two peaks at 283.9 and 283.4 eV in the spectrum at 100 K are attributed to the two carbon atoms of ethylene 21,22 . The changes seen around 180 K in the heat map of C1s spectra recorded during heating ( Fig.…”

Section: Resultsmentioning

confidence: 98%

“…1b) are attributed to a combination of ethylene desorption and decomposition, the latter producing 0.12 monolayer (ML) acetylene (C 2 H 2ad ) + 0.24 ML H ad . The C1s spectrum of adsorbed acetylene shows a peak at 283.3 eV, which accounts for both carbon atoms and is accompanied by two small shoulders at +0.37 and +0.74 eV due excitation (double excitation) of the C-H stretching vibration [21][22][23] . Acetylene remains stable up to 400 K where it dehydrogenates completely (see H 2 desorption data reported below).…”

Section: Resultsmentioning

confidence: 99%

Mechanistic insight into carbon-carbon bond formation on cobalt under simulated Fischer-Tropsch synthesis conditions

et al. 2020

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Facile CC bond formation is essential to the formation of long hydrocarbon chains in Fischer-Tropsch synthesis. Various chain growth mechanisms have been proposed previously, but spectroscopic identification of surface intermediates involved in CC bond formation is scarce. We here show that the high CO coverage typical of Fischer-Tropsch synthesis affects the reaction pathways of C 2 H x adsorbates on a Co(0001) model catalyst and promote CC bond formation. In-situ high resolution x-ray photoelectron spectroscopy shows that a high CO coverage promotes transformation of C 2 H x adsorbates into the ethylidyne form, which subsequently dimerizes to 2-butyne. The observed reaction sequence provides a mechanistic explanation for CO-induced ethylene dimerization on supported cobalt catalysts. For Fischer-Tropsch synthesis we propose that CC bond formation on the close-packed terraces of a cobalt nanoparticle occurs via methylidyne (CH) insertion into long chain alkylidyne intermediates, the latter being stabilized by the high surface coverage under reaction conditions.

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“…miR-181 family members have been reported to be tumor suppressors in glioma 16 17 18 19 20 , but there have been no reports on the role of the miR-181 family as a whole. The aberrant expression of the entire miR-181 family is highly correlated with the prognosis and progression of glioma.…”

Section: Discussionmentioning

confidence: 99%

Upregulation of miR-181s reverses mesenchymal transition by targeting KPNA4 in glioblastoma

Wang

Tao

Yan

et al. 2015

Sci Rep

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The goal of this work was to explore the most effective miRNAs affecting glioblastoma multiforme (GBM) phenotype transition and malignant progression. We annotated 491 TCGA samples’ miRNA expression profiles according to their mRNA-based subtypes and found that the mesenchymal tumors had significantly decreased miR-181 family expression compared with the other three subtypes while the proneural subtype harbored extremely high miR-181 family expression. Patients with high miR-181 family expression had longer overall survival (p = 0.0031). We also confirmed that NF-κB-targeting genes and the EMT (epithelial-mesenchymal transition) pathway were inversely correlated with miR-181 family expression and that the entire miR-181 family inhibited glioma cell invasion and proliferation; of these, miR-181b was the most effective suppressor. Furthermore, miR-181b was validated to suppress EMT by targeting KPNA4 and was associated with survival outcome in the TCGA and CGGA datasets and in another independent cohort. The EMT-inhibitory effect of miR-181b was lost after KPNA4 expression was restored. We also identified the antitumorigenic activity of miR-181b in vitro and in vivo. Our results showed that miR-181 family expression was closely correlated with TCGA subtypes and patients’ overall survival, indicating that miR-181b, a tumor-suppressive miRNA, could be a novel therapeutic candidate for treating gliomas.

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Ethene adsorption and dehydrogenation on clean and oxygen precovered Ni(111) studied by high resolution x-ray photoelectron spectroscopy

Cited by 26 publications

References 38 publications

Adsorption and Decomposition of Ethene and Propene on Co(0001): The Surface Chemistry of Fischer–Tropsch Chain Growth Intermediates

Adsorption and Decomposition of Ethene and Propene on Co(0001): The Surface Chemistry of Fischer–Tropsch Chain Growth Intermediates

Mechanistic insight into carbon-carbon bond formation on cobalt under simulated Fischer-Tropsch synthesis conditions

Upregulation of miR-181s reverses mesenchymal transition by targeting KPNA4 in glioblastoma

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