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31.
Synthesis of a Cu/ZnO Nanocomposite by Electroless Plating for the Catalytic Conversion of CO2 to Methanol
Maja Pori, Iztok Arčon, Marjan Marinšek, Goran Dražić, Blaž Likozar, Zorica Crnjak Orel, Damjan Lašič Jurković, 2019, izvirni znanstveni članek

Opis: The process of methanol synthesis based on the hydrogenation of CO2 was investigated over binary Cu/ZnO catalyst materials, prepared by applying a novel electroless plating fabrication method. The activity of the produced catalytic samples was determined at temperature range between 200 and 300 °C and the feedstock conversion data were supplemented with a detailed microstructure analysis using high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and Cu and Zn K-edge, X-ray absorption near-edge structure (XANES) measurements and extended X-ray absorption fine-structure (EXAFS) measurements. It was confirmed that the disorder in the Cu crystallites created unique geometrical situations, which acted as the additional reactive centres for the adsorption of the reactant molecule species. Copper and zinc structural synergy (spill-over) was also demonstrated as being crucial for the carbon dioxide’s activation. EXAFS and XANES results provide strong evidence for surface alloying between copper and zinc and thus the present results demonstrate new approach applicable for explaining metal–support interactions.
Najdeno v: ključnih besedah
Povzetek najdenega: ...structure (XANES) measurements and extended X-ray absorption fine-structure ( EXAFS) measurements. It was confirmed that the disorder...
Ključne besede: EXAFS, CuZn alloy, Spillover mechanism, CO2 valorization, Electroless deposition method, Heterogeneous catalysis
Objavljeno: 12.04.2019; Ogledov: 486; Prenosov: 0
.pdf Polno besedilo (1,92 MB)

32.
New Insights into Manganese Local Environment in MnS-1Nanocrystals
Alenka Ristić, Matjaž Mazaj, Iztok Arčon, Nina Daneu, Nataša Zabukovec Logar, Roger Glaser, Nataša Novak Tušar, 2019, izvirni znanstveni članek

Opis: Manganese plays an important role in redox catalysis using zeolites as inorganic support materials, but the formation of the preferred redox manganese species (framework or extraframework) is still not well understood. Herein, the influence of the amount of manganese together with conventional and microwave-assisted hydrothermal synthesis paths on the formation of manganese species within the zeolite silicalite-1 (S-1) with MFI structure was investigated. It was found out that both synthesis procedures led to the formation of framework and extraframework manganese species, but in different molar ratios. However, the conventional synthesis procedure with all Mn/Si molar ratios generates more framework Mn in comparison to the microwave procedure. Additionally, the diminution of the zeolite crystals to nanoscale from 100 to 200 nm was achieved via the conventional procedure for the first time. UV–vis, Raman, and X-ray absorption spectroscopic analyses revealed different local environments of manganese: Mn3+ incorporated into the silicalite-1 framework as “framework manganese” and Mn2+/3+ present as “extraframework manganese” (Mn2O3, Mn3O4). TEM reveals the presence of Mn3O4 nanorods. Both framework manganese and extraframework manganese exhibit good catalytic activity for styrene epoxidation. Catalytic results suggest that, in oxidation reactions of hydrocarbons, framework manganese is more active at lower Mn contents (Mn/Si < 0.015), whereas extraframework manganese is more active at higher loadings (Mn/Si > 0.015).
Najdeno v: ključnih besedah
Povzetek najdenega: ...MnS-1 Nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis...
Ključne besede: MnS-1 Nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis
Objavljeno: 06.05.2019; Ogledov: 439; Prenosov: 0
.pdf Polno besedilo (9,33 MB)

33.
Arabidopsis halleri shows hyperbioindicator behaviour for Pb and leaf Pb accumulation spatially separated from Zn
Stephan Höreth, Paula Pongrac, Marta Debeljak, Katarina Vogel-Mikuš, Matic Pečovnik, Primož Vavpetič, Iztok Arčon, izvirni znanstveni članek

Opis: Lead (Pb) ranks among the most problematic environmental pollutants. Background contamination of soils is nearly ubiquitous, yet plant Pb accumulation is barely understood. In a survey covering 165 European populations of the metallophyte Arabidopsis halleri, several field samples had indicated Pb hyperaccumulation, offering a chance to dissect plant Pb accumulation. Accumulation of Pb was analysed in A. halleri individuals from contrasting habitats under controlled conditions to rule out aerial deposition as a source of apparent Pb accumulation. Several elemental imaging techniques were employed to study the spatial distribution and ligand environment of Pb. Regardless of genetic background, A. halleri individuals showed higher shoot Pb accumulation than A. thaliana. However, dose–response curves revealed indicator rather than hyperaccumulator behaviour. Xylem sap data and elemental imaging unequivocally demonstrated the in planta mobility of Pb. Highest Pb concentrations were found in epidermal and vascular tissues. Distribution of Pb was distinct from that of the hyperaccumulated metal zinc. Most Pb was bound by oxygen ligands in bidentate coordination. A. halleri accumulates Pb whenever soil conditions render Pb phytoavailable. Considerable Pb accumulation under such circumstances, even in leaves of A. thaliana, strongly suggests that Pb can enter food webs and may pose a food safety risk.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Pb accumulation, XANES, EXAFS, Arabidopsis halleri...
Ključne besede: Pb accumulation, XANES, EXAFS, Arabidopsis halleri
Objavljeno: 16.01.2020; Ogledov: 116; Prenosov: 0
.pdf Polno besedilo (4,46 MB)

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