Atom Pair Frequencies as a Quantitative Structure–Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt–Iron–Spinel

Geiss, Jeremias; Falk, Tobias; Ognjanović, Stevan; Anke, Sven; Peng, Baoxiang; Winterer, Markus

doi:10.1021/acs.jpcc.2c00788

Cited by 5 publications

(3 citation statements)

References 41 publications

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“…Interestingly, the propene yields were increased during cooling. The results suggest that oxidative dehydrogenation yielding acetone and water was the dominant reaction pathway over all catalysts, which is the usual behavior of Co-based oxides. ,,− Even in the absence of O 2 , the predominant reaction pathway first follows an oxidative dehydrogenation, as probed by 2-propanol decomposition experiments in previous studies. , …”

Section: Resultsmentioning

confidence: 57%

Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Falk

Budiyanto

Dreyer

et al. 2022

ACS Appl. Nano Mater.

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A series of transition-metal-substituted (M = Cr, Mn, Fe, Ni, Cu) ordered mesoporous cobalt oxide catalysts were synthesized via nanocasting method using KIT-6 silica as a hard template. While the pristine Co 3 O 4 formed as a perfect replication of KIT-6, metal substitution resulted in less ordered and smaller domains of the replica oxides. The catalysts were applied in the selective oxidation of 2-propanol in the gas phase to reveal the role of the systematic metal substitution. Cu and Ni substitutions were found to be beneficial for the catalytic activity, while Cr, Mn, and Fe substitutions were detrimental. Cofeeding water vapor shifted the onset temperature of 2-propanol conversion to higher temperatures (ΔT = 10−20 K), while a beneficial effect was observed at high temperatures (>260 °C) decreasing deactivation by slowing the reduction of active Co 3+ and/or reducing coke deposition. The activity scaled with the reducibility of the catalysts probed by H 2 temperature-programmed reduction with the positive effect of a higher reducibility, indicating the crucial role of oxygen activation during 2-propanol oxidation at the gas− solid interface. 2-Propanol activation probed by adsorption/desorption experiments monitored by diffuse reflectance infrared Fourier transform spectroscopy showed a weakening of the interaction and changing of the adsorption mode from dissociative to molecular adsorption following the periodic table from Cr to Cu, suggesting that the activation of 2-propanol plays a minor role compared with oxygen activation. Fe-substituted Co 3 O 4 was the least active catalyst due to the decrease of the number of active Co 3+ sites.

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Section: Resultsmentioning

confidence: 57%

Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Falk

Budiyanto

Dreyer

et al. 2022

ACS Appl. Nano Mater.

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“…RMC analysis of the EXAFS data is performed using the rmcxas code − starting from different initial atomic configurations as models. RMC analysis models the EXAFS data by refining a physical model (atom configuration) based on the difference between experimental and simulated EXAFS spectra via the partial pair distribution functions (pPDFs) using a Metropolis Monte Carlo algorithm .…”

Section: Methodsmentioning

confidence: 99%

Very Small Nanocrystalline Tin Dioxide Particles: Local-, Crystal-, and Micro-Structure

Mackert,

Winter,

Jackson

et al. 2023

J. Phys. Chem. C

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In case of very small nanocrystals, the surface is the dominant defect, generating a microstructure as deviation from the ideal crystal structure by breaking the translational symmetry of the lattice. This heterogeneous disorder may be observed as a different local structure in the core and shell of the nanocrystals and is highly relevant in all properties and applications for which defects are detrimental or beneficial, for example, charge-carrier traps in (opto-)electronics or active surface sites in heterogeneous catalysis. Very small SnO 2 nanocrystals generated by chemical vapor synthesis with coherent diffracting domain sizes between 2 and 13 nm are investigated as a model system since they form phase-pure stannic oxide isostructural to rutile. Local structure, crystal structure, and microstructure are studied using X-ray absorption spectroscopy, wide-angle X-ray scattering, X-ray diffraction, and transmission electron microscopy analyzed using reverse Monte Carlo simulations, Rietveld refinement, and image analysis. Size, surface, and interface effects as well as structural defects are discussed. The fraction of atoms at surfaces is substantial for very small nanoparticles. However, only very subtle structural changes are observed here for very small SnO 2 nanocrystals as revealed by detailed quantitative structural analysis. This may be because the particles are highly crystalline even for the ultrasmall 2 nm particles which are close to the molecular cluster regime.

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“…However, only a small number of XAS studies on the La K-edge of lanthanum-based oxides exist at the high edge energy of 39 keV, which is only available at a few beamlines. , While multiple X-ray absorber sites of LaCo 1– x Fe x O 3 provide a detailed XAS data set of the local structure, a mutual quantitative analysis is challenging. One method is Reverse Monte Carlo (RMC) analysis, which allows the refinement of a mutual, structural model using data sets from multiple absorber sites simultaneously. − The RMC models consist of discrete atoms inside a simulation box, which enables the representation of complex strucure such as multiphase systems of nanoparticles. , …”

Section: Introductionmentioning

confidence: 99%

LaCo_1–xFe_xO₃ Nanoparticles in Cyclohexene Oxidation

et al. 2023

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The identification of structure−activity relationships is challenging for complex oxides like lanthanum-based perovskite nanoparticles. The purpose of this study is to examine the structure of LaCo 1−x Fe x O 3 nanoparticles and develop a detailed structural model to identify subtle changes of the structure after catalysis. Therefore, small nanoparticles with a significant fraction of surface atoms and varying iron content (x = 0, 0.5, 1) are synthesized in the gas phase by chemical vapor synthesis and tested in cyclohexene oxidation in the liquid phase. The crystal structure is examined by X-ray and selected area electron diffraction. Additionally, the local structure of the cations is probed by Xray absorption spectroscopy at the Co, Fe, La K, and La L 3 -edges. For a quantitative analysis of the local structure before and after catalysis, an atomistic model is refined by the available extended X-ray absorption fine structure spectra using Reverse Monte Carlo methods. The produced nanoparticles are small with a coherent diffraction domain size between 5 and 10 nm, highly crystalline, and consist mainly of the perovskite phase with a secondary spinel phase. In cyclohexene oxidation, the cobalt-containing samples exhibit significant catalytic activities. The active samples show structural changes after catalysis accompanied by reconstruction of the local structure surrounding the cations in the perovskite phase, which resembles edge-sharing cobalt octahedra.

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Atom Pair Frequencies as a Quantitative Structure–Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt–Iron–Spinel

Cited by 5 publications

References 41 publications

Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Very Small Nanocrystalline Tin Dioxide Particles: Local-, Crystal-, and Micro-Structure

LaCo_1–xFe_xO₃ Nanoparticles in Cyclohexene Oxidation

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Atom Pair Frequencies as a Quantitative Structure–Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt–Iron–Spinel

Cited by 5 publications

References 41 publications

Doping of Nanostructured Co3O4 with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Doping of Nanostructured Co3O4 with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Very Small Nanocrystalline Tin Dioxide Particles: Local-, Crystal-, and Micro-Structure

LaCo1–xFexO3 Nanoparticles in Cyclohexene Oxidation

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Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

Doping of Nanostructured Co₃O₄ with Cr, Mn, Fe, Ni, and Cu for the Selective Oxidation of 2-Propanol

LaCo_1–xFe_xO₃ Nanoparticles in Cyclohexene Oxidation