References of "de Jongh, Petra"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailSmall-Angle Scattering Analysis of Empty or Loaded Hierarchical Porous Materials
Gommes, Cédric ULg; Prieto, Gonzalo; de Jongh, Petra

in Journal of Physical Chemistry C (2016), 120(3), 14881506

Small-angle scattering of x-rays (SAXS) or neutrons (SANS) is one of the few experimental methods that can in principle be used for the in situ study at the mesoscopic scale of physicochemical phenomena ... [more ▼]

Small-angle scattering of x-rays (SAXS) or neutrons (SANS) is one of the few experimental methods that can in principle be used for the in situ study at the mesoscopic scale of physicochemical phenomena occurring inside nanoporous solids. However, the potential of the method is often limited by the lack of suitable data analysis methods to convert scattering data into real-space structural information. This is notably the case for most porous materials of practical interest, which exhibit a hierarchical structure with micro, meso, and macropores, with often a secondary material confined in the pores, such as in supported catalysts, as well as fuel-cell and battery materials. In the present contribution, we propose a general analysis of x-ray scattering by this type of material. Assuming that each structural level is statistically independent from the others and has a distinct characteristic length scale, compact mathematical expressions are derived for the scattering of the entire hierarchical structure. The results are particularised to the SAXS analysis of SBA-15 ordered mesoporous silica loaded with copper nitrate as well as to supported catalysts obtained after heat treatment of that material. The SAXS data analysis shows that the nitrate fills both the micro and mesopores of the material, while the metallic copper obtained after heat treatment is found only in the mesopores. Moreover, the mesoscopic-scale spatial distribution of the metal depends on the heat treatment, in line with earlier electron tomography studies. The main ideas underlying the SAXS data analysis were presented in an recent Communication [Gommes et al., Angew. Chem. Intl. Ed. 54 (2015) 11804-11808]. Here we generalise the approach and we provide a comprehensive discussion of how any level in a hierarchical structure contributes to its overall scattering pattern. The results, as well as the general modelling methodology, will be of interest to anyone interested in the quantitative analysis of small-angle scattering data of empty or loaded porous solids, and more generally of any type of hierarchical material. [less ▲]

Detailed reference viewed: 100 (16 ULg)
Full Text
Peer Reviewed
See detailMesoscale Characterization of Nanoparticles Distribution Using X-Ray Scattering
Gommes, Cédric ULg; Prieto, Gonzalo; Zecevic, Jovana et al

in Angewandte Chemie International Edition (2015), 54

The properties of many functional materials depend critically on the spatial distribution of an active phase within a matrix or support material. In the case of solid catalysts, controlling the spatial ... [more ▼]

The properties of many functional materials depend critically on the spatial distribution of an active phase within a matrix or support material. In the case of solid catalysts, controlling the spatial distribution of metal (oxide) nanoparticles at the mesoscopic scale offers new strategies to tune their performance and enhance their lifetimes. However, such advanced control requires the development of suitable methods to characterize the spatial distribution of nanoparticles at the mesoscopic scale. Currently electron microscopy and more specifically electron tomography is close to being the only option. Here, we show how the background in x-ray scattering patterns can be analyzed to quantitatively access the distribution of metal nanoparticles within support materials displaying hierarchical porosity. Our approach is illustrated for copper catalysts supported on meso- and micro-porous silica, which display distinctly different metal spatial distributions. Results derived from the modeling of x-ray scattering patterns are in excellent agreement with electron tomography observations, while the amount of material being characterized at once is enhanced by twelve orders of magnitude. Our strategy opens unprecedented prospects to understand structure-property relationships and to guide the synthesis of advanced supported catalysts as well as a wide array of other functional nanomaterials. [less ▲]

Detailed reference viewed: 185 (14 ULg)
Full Text
Peer Reviewed
See detailSupport Functionalization To Retard Ostwald Ripening in Copper Methanol Synthesis Catalysts
Van den Berg, Roy; Parmentier, Tanja; Elkjaer, Christian et al

in ACS Catalysis (2015), 5

A main reason for catalyst deactivation in supported catalysts for methanol synthesis is copper particle growth. We have functionalized the support surface in order to suppress the formation and/or ... [more ▼]

A main reason for catalyst deactivation in supported catalysts for methanol synthesis is copper particle growth. We have functionalized the support surface in order to suppress the formation and/or transport of mobile copper species and thereby catalyst deactivation. A Stöber silica support was functionalized by treatment with aminopropyltriethoxysilane, which introduces aminopropyl groups on the surface. Copper was deposited on both unfunctionalized and functionalized Stöber silica via incipient wetness impregnation with aqueous copper nitrate solutions followed by drying and calcination. Similar particle size distributions (1−5 nm) were obtained for both supports by changing the flow of N2 to a flow of 2% NO/N2 during calcination of the unfunctionalized and amine functionalized silica, respectively. The effect of support functionalization with aminopropyl groups was an increased stability in the methanol synthesis reaction (40 bar, 260 °C, 23% CO/7% CO2/60% H2/10% Ar, 3% COx conversion) due to more limited copper particle growth as determined by transmission electron microscopy (TEM). Changing the interparticle distance did not have an influence on the deactivation rate, while the addition of few very large copper particles did, indicating that Ostwald ripening was most probably the dominant particle growth mechanism for these samples. In situ TEM images showed the contact angle between the reduced copper particles and the support. As shape and size was similar on silica as on amine-functionalized silica, the thermodynamic stability of the copper particles was unaltered. The driving force for copper particle growth was thus unchanged upon functionalization. We therefore suggest that Ostwald ripening in methanol synthesis catalysts was retarded by inhibiting the transport of copper species over the support surface. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed a decrease in the number of surface groups (hydroxyl, methoxy, and aminopropyl) upon functionalization because aminopropyltriethoxysilane reacted with multiple hydroxyl groups. Because of that, the distance between neighboring functional groups was increased, suppressing the mobility of Ostwald ripening species from one copper particle to another. [less ▲]

Detailed reference viewed: 118 (3 ULg)
Full Text
Peer Reviewed
See detailModeling reaction-limited Ostwald ripening of supported Ni catalysts in presence of CO: the role of particle size distribution
Gommes, Cédric ULg; Munnik, Peter; de Jongh, Petra et al

Poster (2014, March)

Detailed reference viewed: 35 (2 ULg)
Full Text
Peer Reviewed
See detailNanoparticle Growth in Supported Nickel Catalysts during Methanation Reaction-Larger is Better
Munnik, Peter; Velthoen, Marjolein; de Jongh, Petra et al

in Angewandte Chemie International Edition (2014), 53

A major cause of supported metal catalyst deactivation is particle growth by Ostwald ripening. Nickel catalysts, used in the methanation reaction, may suffer greatly from this through the formation of [Ni ... [more ▼]

A major cause of supported metal catalyst deactivation is particle growth by Ostwald ripening. Nickel catalysts, used in the methanation reaction, may suffer greatly from this through the formation of [Ni(CO)4]. By analyzing catalysts with various particle sizes and spatial distributions, the interparticle distance was found to have little effect on the stability, because formation and decomposition of nickel carbonyl rather than diffusion was rate limiting. Small particles (3–4 nm) were found to grow very large (20–200 nm), involving local destruction of the support, which was detrimental to the catalyst stability. However, medium sized particles (8 nm) remained confined by the pores of the support displaying enhanced stability, and an activity 3 times higher than initially small particles after 150 h. Physical modeling suggests that the higher [Ni(CO)4] supersaturation in catalysts with smaller particles enabled them to overcome the mechanical resistance of the support. Understanding the interplay of particle size and support properties related to the stability of nanoparticles offers the prospect of novel strategies to develop more stable nanostructured materials, also for applications beyond catalysis. [less ▲]

Detailed reference viewed: 130 (10 ULg)
Full Text
Peer Reviewed
See detailMesoporosity of Zeolite Y – 3D Quantitative Study by Image Analysis of Electron Tomograms
Zecevic, Jovana; Gommes, Cédric ULg; friedrich, Heiner et al

in Angewandte Chemie International Edition (2012), 51

Detailed reference viewed: 31 (3 ULg)
See detailCharacterization of nanometer-scale roughness in SBA-15 mesoporous silica using image analysis of electron tomograms
Friedrich, Heiner; Gommes, Cédric ULg; de Jongh, Petra et al

Conference (2009, September)

Detailed reference viewed: 16 (0 ULg)
See detailQuantization of pore corrugation in SBA-15 by image analysis of electron tomograms
Friedrich, Heiner; Gommes, Cédric ULg; de Jongh, Petra et al

Conference (2009, March)

Detailed reference viewed: 22 (0 ULg)
Full Text
Peer Reviewed
See detailQuantitative Structural Analysis of Binary Nanocrystal Superlattices by Electron Tomography
Friedrich, Heiner; Gommes, Cédric ULg; Overgaag, Karin et al

in Nano Letters (2009), 9

Binary nanocrystal superlattices, that is, ordered structures of two sorts of nanocolloids, hold promise for a series of functional materials with novel collective properties. Here we show that based on ... [more ▼]

Binary nanocrystal superlattices, that is, ordered structures of two sorts of nanocolloids, hold promise for a series of functional materials with novel collective properties. Here we show that based on electron tomography a comprehensive, quantitative, three-dimensional characterization of these systems down to the single nanocrystal level can be achieved, which is key in understanding the emerging materials properties. On four binary lattices composed of PbSe, CdSe, and Au nanocrystals, we illustrate that ambiguous interpretations based on two-dimensional transmission electron microscopy can be prevented, nanocrystal sizes and superlattice parameters accurately determined, individual crystallographic point and plane defects studied, and the order/disorder at the top and bottom surfaces imaged. Furthermore, our results suggest that superlattice nucleation and growth occurred at the suspension/air interface and that the unit cells of some lattices are anisotropically deformed upon drying. [less ▲]

Detailed reference viewed: 37 (1 ULg)
Full Text
Peer Reviewed
See detailQuantitative Characterization of Pore Corrugation in Ordered Mesoporous Materials Using Image Analysis of Electron Tomograms
Gommes, Cédric ULg; Friedrich, Heiner; Wolters, Mariska et al

in Chemistry of Materials (2009), 21

Electron tomography and image analysis are combined to characterize ordered mesoporous silica SBA-15. The morphology of the mesopores with average diameter 6 nm is analyzed in terms of cylinders having ... [more ▼]

Electron tomography and image analysis are combined to characterize ordered mesoporous silica SBA-15. The morphology of the mesopores with average diameter 6 nm is analyzed in terms of cylinders having variable radii and centers that are statistically centered on the points of a distorted hexagonal lattice. The variations in the mesopore centers and radii add up and result in pore wall corrugation with amplitude of 1.6 nm. The correlation length of the corrugation along the pore axis was found to be 4-5 nm. The amplitude of the corrugation compared well with the 1.9 nm thick microporous corona obtained from X-ray diffraction (XRD). In general, the present approach provides a detailed microscopic 3D model of nanostructured materials that complements macroscopic measurements such as physisorption and XRD. [less ▲]

Detailed reference viewed: 56 (3 ULg)
Peer Reviewed
See detailQuantitative characterization of pore corrugation in SBA-15 mesoporous silica using image analysis of electron tomograms
Gommes, Cédric ULg; Friedrich, Heiner; Wolters, Mariska et al

Poster (2008, September)

Detailed reference viewed: 12 (1 ULg)
Peer Reviewed
See detailNi/SiO2 Catalyst Preparation Studies using SBA-15 as a Model Support and quantitative Electron Tomography Characterisation
de Jongh, Petra; Friedrich, Heiner; Gommes, Cédric ULg et al

Poster (2008, September)

Detailed reference viewed: 17 (0 ULg)
See detailAnalysis of 3DTEM and SAXS of ordered mesoporous silica with the same stochastic morphological model
Gommes, Cédric ULg; Friedrich, Heiner; Wolters, Mariska et al

Scientific conference (2008, May)

Detailed reference viewed: 21 (0 ULg)