The active sites of a working Fischer–Tropsch catalyst revealed by operando scanning tunnelling microscopy

Böller, Bernhard; Durner, Katharina M.; Wintterlin, Joost

doi:10.1038/s41929-019-0360-1

Cited by 78 publications

(120 citation statements)

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“…An in situ X-ray absorption study of cobalt supported on a carbon nanofiber support shows that neither bulk oxidation nor substantial surface oxidation occurs on cobalt during FTS 14 . Furthermore, cobalt single crystals were found to be active for FTS 11,[15][16][17][18] , and the turnover frequencies reported are similar to those found for supported catalysts. This confirms that metallic cobalt is the active phase for chain growth and that insights from single crystal studies are of direct relevance for fundamental understanding of FTS.…”

supporting

confidence: 66%

“…The experimentally observed surface reactions presented here show that C-C bond formation via alkylidyne coupling is favourable on the close-packed terraces that constitute~60% of the surface of an (fcc-)Co nanoparticle 4,41 . The methylidyne monomers required for chain growth during FTS can either be supplied via H-assisted routes on the terrace or via spill-over from adjacent step sites that are active for CO dissociation 18,50 and surround the nm-sized close-packed terrace exposed by an fcc-Co nanoparticle 4 . An fcc-Co nanoparticle also exposes (100) facets as well as step and kink sites 51 , and the role of the different structural elements remains a topic of debate 52 .…”

Section: Discussionmentioning

confidence: 99%

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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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confidence: 66%

Section: Discussionmentioning

confidence: 99%

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

et al. 2020

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“…ethane, the simplest alkane, is the principal component of natural gas and shale gas, which is a highly abundant and inexpensive carbon source of fuel and chemicals. Therefore, a development of the catalytic process that can directly convert methane into valuable chemicals leads to the effective use of methane as carbon source, and intensive efforts have been devoted to develop this catalytic process [1][2][3][4][5][6][7] . However, a technological breakthrough has been remained.…”

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confidence: 99%

Zeolite-supported ultra-small nickel as catalyst for selective oxidation of methane to syngas

et al. 2020

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The development of simple catalysts with high performance in the selective oxidation of methane to syngas at low temperature has attracted much attention. Here we report a nickel-based solid catalyst for the oxidation of methane, synthesised by a facile impregnation method. Highly dispersed ultra-small NiO particles of 1.6 nm in size are successfully formed on the MOR-type zeolite. The zeolite–supported nickel catalyst gives continuously 97–98% methane conversion, 91–92% of CO yield with a H2/CO ratio of 2.0, and high durability without serious carbon deposition onto the catalyst at 973 K. DFT calculations demonstrate the effect of NiO particle size on the C-H dissociation process of CH4. A decrease in the NiO particle size enhances the production of oxygen originating from the NiO nanoparticles, which contributes to the oxidation of methane under a reductive environment, effectively producing syngas.

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“…The migration and transformation of intrinsic and extrinsic crystal defects play a central role in numerous materials science and chemistry phenomena, such as postirradiation annealing 1,2 , plasma surface interactions 3 , or active site formation for heterogeneous catalysis 4,5 . The atomistic mechanisms by which defects migrate are generally impossible to divine a priori due to the routine presence of complex multiatom transformations [6][7][8][9][10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

Automated calculation and convergence of defect transport tensors

Swinburne

Pérez

2020

npj Comput Mater

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Defect diffusion is a key process in materials science and catalysis, but as migration mechanisms are often too complex to enumerate a priori, calculation of transport tensors typically have no measure of convergence and require significant end-user intervention. These two bottlenecks prevent high-throughput implementations essential to propagate model-form uncertainty from interatomic interactions to predictive simulations. In order to address these issues, we extend a massively parallel accelerated sampling scheme, autonomously controlled by Bayesian estimators of statewide sampling completeness, to build atomistic kinetic Monte Carlo models on a state-space irreducible under exchange and space group symmetries. Focusing on isolated defects, we derive analytic expressions for drift and diffusion coefficients, providing a convergence metric by calculating the Kullback–Leibler divergence across the ensemble of diffusion processes consistent with the sampling uncertainty. The autonomy and efficacy of the method is demonstrated on surface trimers in tungsten and Hexa-interstitials in magnesium oxide, both of which exhibit complex, correlated migration mechanisms.

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The active sites of a working Fischer–Tropsch catalyst revealed by operando scanning tunnelling microscopy

Cited by 78 publications

References 50 publications

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

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

Zeolite-supported ultra-small nickel as catalyst for selective oxidation of methane to syngas

Automated calculation and convergence of defect transport tensors

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