1. XAS analysis of bifunctional Ni/ZSM-5 catalystsIztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2024, published scientific conference contribution abstract Abstract: In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al
and Ni contents [1]. Here we present a systematic structural study of the Ni/ZSM-5 materials by Ni
K-edge XANES and EXAFS analyses, to monitor the changes of local structure and chemical state
of Ni species in the catalysts as a function of Al and Ni content. A series of Ni/ZSM-5 type zeolites
with different Al to Si and Ni to Si molar ratios were synthesized by a “green”, template free technique
[2]. With a combination of XAS, XRD and TEM we resolved the changes in the local environment
of Ni species induced by the different Al contents in the
Ni/ZSM-5 catalysts.
Ni species in Ni/ZSM-5 exist as NiO nanocrystals and as
charge compensating Ni2+ cations. The Ni K-edge
XANES and EXAFS results enabled the quantification
of Ni-containing species. At a low Al to Si ratio (nAl/nSi
< 0.04), the NiO nanoparticles predominate in the
samples and account for over 65% of Ni phases.
However, NiO is outnumbered by Ni2+ cations attached
to the zeolite framework in ZSM-5 with a high Al to Si
ratio (nAl/nSi = 0.05) due to a higher number of
framework negative charges imparted by Al. The
obtained results show that the number of highly reducible
and active NiO nanocrystals is strongly correlated with
the framework Al sites present in Ni/ZSM-5 zeolites.
Keywords: Ni EXAFS, XANES Ni/ZSM-5 catalyst
Published in RUNG: 05.07.2024; Views: 910; Downloads: 3
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2. Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts by Ni K-edge XAS analysisIztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2023, published scientific conference contribution abstract Abstract: Catalyst design is crucial for improving catalytic activity and product selectivity. In a bifunctional Ni/ZSM-5
zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents [1]. While changes in
acid properties associated with Al sites are usually closely investigated, Ni phases, however, receive inadequate
attention. Herein, we present a systematic structural study of Ni in the Ni/ZSM-5 materials by Ni K-edge
XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) analyses,
to monitor the local structure and chemical state of Ni species in the catalysts. In combination with XRD and
TEM we resolved the changes in the local environment of Ni species induced by the different Al contents of
the parent ZSM-5 prepared by a “green”, template free technique [2].
Ni species in Ni/ZSM-5 exist as NiO crystals (3–50 nm) and as charge compensating Ni2+ cations. The Ni Kedge
XANES and EXAFS results enabled the quantification of Ni-containing species. At a low Al to Si ratio
(nAl/nSi < 0.04), the NiO nanoparticles predominate in the samples and account for over 65% of Ni phases.
However, NiO is outnumbered by Ni2+ cations attached to the zeolite framework in ZSM-5 with a high Al to Si
ratio (nAl/nSi = 0.05) due to a higher number of framework negative charges imparted by Al. The obtained
results show that the number of highly reducible and active NiO crystals is strongly correlated with the
framework Al sites present in ZSM-5 zeolites, which depend greatly on the synthesis conditions. Therefore,
this kind of study is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other
metal-modified bifunctional catalysts.
Keywords: Ni/ZSM-5 catalysts, Ni EXAFS, XANES
Published in RUNG: 19.09.2023; Views: 1768; Downloads: 5
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3. Periodic anti-phase boundaries and crystal superstructures in ▫$PtCu_3$▫ nanoparticles as fuel cell electrocatalystsAna Rebeka Kamšek, Anton Meden, Iztok Arčon, Primož Jovanovič, Martin Šala, Francisco Ruiz-Zepeda, Goran Dražić, Miran Gaberšček, Marjan Bele, Nejc Hodnik, 2023, original scientific article Published in RUNG: 19.09.2023; Views: 1813; Downloads: 9
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4. Multicomponent Cu-Mn-Fe silica supported catalysts to stimulate photo-Fenton-like water treatment under sunlightAndraž Šuligoj, Ivalina Trendafilova, Ksenija Maver, Albin Pintar, Alenka Ristić, Goran Dražić, Wael H. M. Abdelraheem, Zvonko Jagličić, Iztok Arčon, Nataša Zabukovec Logar, Dionysios D. Dionysiou, Nataša Novak Tušar, original scientific article Keywords: Magnetic catalyst, Photocatalyst, Water treatment, Sunlight, Contaminants of emerging concern, Photo-Fenton-like systems, Cu, Mn, Fe, XANES, EXAFS
Published in RUNG: 06.07.2023; Views: 2525; Downloads: 9
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5. Winning combination of Cu and Fe oxide clusters with an alumina support for low-temperature catalytic oxidation of volatile organic compoundsTadej Žumbar, Iztok Arčon, Petar Djinović, Giuliana Aquilanti, Gregor Žerjav, Albin Pintar, Alenka Ristić, Goran Dražić, Janez Volavšek, Gregor Mali, Margarita Popova, Nataša Zabukovec Logar, Nataša Novak Tušar, 2023, original scientific article Abstract: A γ-alumina support functionalized with transition metals is one of the most widely used industrial catalysts for the total oxidation of volatile organic compounds (VOCs) as air pollutants at higher temperatures (280−450 °C). By rational design of a
bimetal CuFe-γ-alumina catalyst, synthesized from a dawsonite alumina precursor, the activity in total oxidation of toluene as a model VOC at a lower temperature (200−380
°C) is achieved. A fundamental understanding of the catalyst and the reaction mechanism is elucidated by advanced microscopic and spectroscopic characterizations as well as by temperature-programmed surface techniques. The nature of the metal−support bonding and the optimal abundance between Cu−O−Al and Fe−O−Al species in the catalysts leads to synergistic catalytic activity promoted by small amounts of iron (Fe/Al = 0.005).
The change in the metal oxide−cluster alumina interface is related to the nature of the
surfaces to which the Cu atoms attach. In the most active catalyst, the CuO6 octahedra are
attached to 4 Al atoms, while in the less active catalyst, they are attached to only 3 Al atoms. The oxidation of toluene occurs via the Langmuir−Hinshelwood mechanism. The presented material introduces a prospective family of low-cost and scalable oxidation catalysts with superior efficiency at lower temperatures.
Keywords: Iron oxide clusters, copper oxide clusters, alumina support, synergistic effect, low-temperature total catalytic oxidation, toluene, Cu, Fe XANES, EXAFS
Published in RUNG: 06.07.2023; Views: 2723; Downloads: 27
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6. Insight into the interdependence of Ni and Al in bifunctional Ni/ZSM-5 catalysts at the nanoscaleHue-Tong Vu, Iztok Arčon, Danilo Oliveira de Souza, Simone Pollastri, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2022, original scientific article Abstract: Catalyst design is crucial for improving catalytic activity and product selectivity. In a bifunctional Ni/ZSM-5
zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents. While changes in
acid properties associated with Al sites are usually closely investigated, Ni phases, however, receive
inadequate attention. Herein, we present a systematic structural study of Ni in the Ni/ZSM-5 materials by
using Ni K-edge XANES and EXAFS analyses, complemented by XRD and TEM, to resolve the changes in
the local environment of Ni species induced by the different Al contents of the parent ZSM-5 prepared
by a “green”, template free technique. Ni species in Ni/ZSM-5 exist as NiO crystals (3–50 nm) and as
charge compensating Ni2+ cations. The Ni K-edge XANES and EXAFS results enabled the quantification
of Ni-containing species. At a low Al to Si ratio (nAl/nSi # 0.04), the NiO nanoparticles predominate in
the samples and account for over 65% of Ni phases. However, NiO is outnumbered by Ni2+ cations
attached to the zeolite framework in ZSM-5 with a high Al to Si ratio (nAl/nSi ¼ 0.05) due to a higher
number of framework negative charges imparted by Al. The obtained results show that the number of
highly reducible and active NiO crystals is strongly correlated with the framework Al sites present in
ZSM-5 zeolites, which depend greatly on the synthesis conditions. Therefore, this kind of study is
beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified
bifunctional catalysts.
Keywords: Ni/ZSM-5 catalysts, zeolite, Ni XANES, EXAFS
Published in RUNG: 11.05.2022; Views: 2533; Downloads: 50
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7. Incorporation of Sc into the structure of barium-hexaferrite nanoplatelets and its ex-traordinary finite-size effect on the magnetic propertiesDarko Makovec, Matej Komelj, Goran Dražić, Blaž Belec, Tanja Goršak, Sašo Gyergyek, Darja lisjak, 2019, original scientific article Keywords: Nanoparticles, Magnetic properties, Size effect, Structure properties relationship, Ferrite.
Published in RUNG: 06.05.2019; Views: 4002; Downloads: 0
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8. Synthesis of a Cu/ZnO Nanocomposite by Electroless Plating for the Catalytic Conversion of CO2 to MethanolMaja Pori, Iztok Arčon, Damjan Lašič Jurković, Marjan Marinšek, Goran Dražić, Blaž Likozar, Zorica Crnjak Orel, 2019, original scientific article Abstract: 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.
Keywords: EXAFS, CuZn alloy, Spillover mechanism, CO2 valorization, Electroless deposition method, Heterogeneous
catalysis
Published in RUNG: 12.04.2019; Views: 4583; Downloads: 0
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10. Bi-magnetic composite nanoplatelets combining hard-magnetic barium hexaferrite core covered with soft magnetic iron oxide layerBlaž Belec, Darko Makovec, Goran Dražić, Benjamin Podmiljšak, Tanja Goršak, Sašo Gyergek, Matej Komelj, Josep Nogues, unpublished invited conference lecture Keywords: bi-magnetic nanoparticles, composite nanoparticles, exchange coupling
Published in RUNG: 05.06.2018; Views: 4748; Downloads: 0
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