Electron microscopy of Pt, Pd and Ni particles in a NaX zeolite matrix

Kleine, Andreas; Ryder, P.L.; Jaeger, Nils; Schulz‐Ekloff, G.

doi:10.1039/f19868200205

Cited by 49 publications

(3 citation statements)

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“…This indicates that although the iron oxide particles had sintered strongly they were most likely still embedded in the carbon matrix. Such a growth of particles within a porous matrix is also known from noble metals in zeolites, where the framework is locally destroyed to allow growth of particles exceeding the sizes of the structural voids . The loss of the catalytic activity can thus be attributed to the formation of larger particles with a lower surface to volume ratio.…”

Section: Resultsmentioning

confidence: 99%

“…Such a growth of particles within a porous matrix is also known from noble metals in zeolites, where the framework is locally destroyed to allow growth of particles exceeding the sizes of the structural voids. 45 The loss of the catalytic activity can thus be attributed to the formation of larger particles with a lower surface to volume ratio. Particle growth by sintering is dependent not only on temperature but also on other factors, such as texture, size, morphology, and the melting point of the particles.…”

Section: Ammonia Decomposition Reactionmentioning

confidence: 99%

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Spatially and Size Selective Synthesis of Fe-Based Nanoparticles on Ordered Mesoporous Supports as Highly Active and Stable Catalysts for Ammonia Decomposition

et al. 2010

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Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

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Section: Resultsmentioning

confidence: 99%

Section: Ammonia Decomposition Reactionmentioning

confidence: 99%

Spatially and Size Selective Synthesis of Fe-Based Nanoparticles on Ordered Mesoporous Supports as Highly Active and Stable Catalysts for Ammonia Decomposition

et al. 2010

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“…The reduction process has shown that Pd atom is more favorable to remain in the zeolite supercages than the sodalite and hexagonal prism [11]. Bergeret et al [14] and Kleine et al [15] have found that the reduction can result in agglomeration of Pd atoms in the supercages with primary particle size less than 7 Å. These particles could extend over several cages at high temperature condition.…”

Section: Introductionmentioning

confidence: 99%

Zeolite supported Pd electrocatalyst nanoparticle characterization

Yao

2019

International Journal of Hydrogen Energy

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Highlights:• Detail Pd cluster structure by the ex-situ Extended X-ray Adsorption Fine Structure (EXAFS) method.• Evaluate Pd/Y-zeolite nanoparticle size under calcinations and reduction temperature.• Measure Pd nanoparticle electrochemical activity in electrolyte solution.• Discuss electrochemical reaction behaviour with respect to Pd particle size.• Explore Pd particle location and Pd particle migration and electrochemical behaviour. AbstractA laboratory made 1.5 wt% Palladium (Pd) zeolite electrocatalyst is investigated using the Extended X-ray Adsorption Fine Structure (EXAFS) and Cyclic Voltammetry (CV) techniques to reveal Pd structure and resultant electrochemical performance. It was found that the Abstract ID 23 -International Journal of Hydrogen Energy 2 electrochemical activity of hydrogen charger transfer in the hydride region increased for electrocatalyst with large-size particles made at high temperature of 400 o C, compared to those with small-size particles calcined and reduced at temperature below 360 o C, at which no major discrepancies were observed between catalysts of different sizes. Furthermore, Pd particle location has played an important role to enhance electrocatalyst performance. The Pd atom tends to remain at small cages, i.e. zeolite sodalite cages or hexagonal prisms at calcinations and reduction temperatures below 360 o C. When temperature increases to about 400 o C, the majority Pd atoms tend to migrate from zeolite small cages to supercages and zeolite external structures with enhanced electrochemical performance.

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and¹,

Löffler²

2002

Handbook of Porous Solids

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Electron microscopy of Pt, Pd and Ni particles in a NaX zeolite matrix

Cited by 49 publications

References 1 publication

Spatially and Size Selective Synthesis of Fe-Based Nanoparticles on Ordered Mesoporous Supports as Highly Active and Stable Catalysts for Ammonia Decomposition

Spatially and Size Selective Synthesis of Fe-Based Nanoparticles on Ordered Mesoporous Supports as Highly Active and Stable Catalysts for Ammonia Decomposition

Zeolite supported Pd electrocatalyst nanoparticle characterization

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