1. Surface acidity and basicity of ZnAlGaOx catalysts supportsLaura Milišić, Blaž Belec, Anja Siher, Gregor Žerjav, Albin Pintar, Andraž Mavrič, 2025, published scientific conference contribution abstract Keywords: surface acidity, surface basicity, ZnAlGaOx catalysts, layered double hydroxide, pyridine temperature-programmed desorption, TPD
Published in RUNG: 20.03.2025; Views: 156; Downloads: 1
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2. Beyond surface area : enhanced pseudocapacitive properties of cobalt layered double hydroxide through structural modificationsAnja Siher, Ksenija Maver, Uroš Luin, Albin Pintar, Iztok Arčon, Andraž Mavrič, 2025, original scientific article Abstract: Cobalt hydroxide and other first-row transition metal hydroxides have gained significant attention as pseudocapacitor materials due to their rapid and reversible redox processes. Their layered structures facilitate interactions between electrolyte anions and cobalt cation sites within the bulk of the material, enabling higher charge density and extending redox activity beyond the particle surface. By controlled precipitation under hydrothermal conditions, the structure and morphology of cobalt hydroxides can be optimized to enhance electrochemical performance. Challenging conventional assumptions, surface area alone is not the primary factor driving increased pseudocapacitive performance. The hexagonal hydrotalcite-like structure, characterized by lower skeletal density and larger basal plane spacing, outperforms the monoclinic cobalt carbonate hydroxide structure, achieving an order of magnitude higher capacitance. In situ X-ray absorption spectroscopy provides critical insights into the pseudocapacitive behavior, revealing enhanced accessibility of Co2+ sites for electrochemical oxidation. While monoclinic cobalt carbonate hydroxide exhibits minimal changes in the Co2+ oxidation state, indicative of surface-limited redox activity, the hydrotalcite-like cobalt hydroxides show substantial shifts in the Co K-edge position, highlighting oxidation of Co2+ sites throughout the bulk.
Keywords: pseudocapacitors, layered-double hydroxides, cobalt hydroxide, redox processes, in situ x-ray absorption spectroscopy
Published in RUNG: 14.03.2025; Views: 336; Downloads: 6
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3. Proučevanje eno in večkovinskih katalizatorjev na silikatnem nosilcu v naprednem oksidacijskem procesu za čiščenje odpadnih voda : magistrsko deloSara Kozjan, 2024, master's thesis Abstract: Ena izmed glavnih onesnaževal v odpadnih vodah so strupene organske spojine, katerih količina se z industrijskim razvojem nenehno povečuje. Najbolj nevarna so tako imenovana zaskrbljujoča onesnaževala (CEC – Contaminants of Emerging Concern), med katerimi so najpogostejših farmacevtski izdelki in izdelki za osebno nego. Za učinkovito odstranjevanje le-teh se raziskave osredotočajo na napredne oksidacijske procese (Advanced Oxidation Processes – AOP), ki s pomočjo katalizatorjev in oksidantov organska onesnaževala oksidirajo v ogljikov dioksid, vodo in mineralne kisline. Magistrska naloga se nanaša na proučevanje eno, dvo in trikovinskih katalizatorjev na silikatnem nosilcu. Kovine, ki smo jih proučevali, so bile baker, mangan in železo.
Katalizatorji so bili sintetizirani na Odseku za anorgansko kemijo in tehnologijo na Kemijskem inštitutu. Katalizatorje smo najprej ovrednotili z osnovnimi karakterizacijskimi metodami, kot so rentgenska difrakcija (XRD – X-Ray Diffraction), dušikova fizisorpcija in vrstična elektronska mikroskopija (SEM – Scanning Electron Microscopy). Ugotovili smo, da imajo višjo vsebnost kovin skoraj vsi kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji, kar lahko pripišemo ekstrakcijskemu postopku, med katerim se najverjetneje odstrani določeno množino kovin iz katalizatorjev. Postopek priprave bistveno ne vpliva na specifično površino, velikost por in volumen por katalizatorjev. Pri kalciniranih katalizatorjih, ki vsebujejo Cu, je le-ta prisoten v obliki CuO.
Katalitske teste sem izvedla na dveh modelnih onesnaževalih iz skupine CEC in sicer na kumarinu (Fenton in foto-Fenton AOP) in glifosatu (Fenton AOP). Ugotovila sem, da so v primeru obeh uporabljenih modelnih onesnaževal najbolj učinkoviti dvokovinski katalizatorji in sicer pri kumarinu katalizator s Cu in Mn ter pri glifosatu katalizator s Cu in Fe. Pri kumarinu katalizator s Cu in Mn kaže tudi na fotokatalitsko aktivnost pri obsevanju z vidno svetlobo. Prav tako sem ugotovila, da so tako kot pri kumarinu tudi pri glifosatu bolj učinkoviti kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji. To lahko pripišemo višji vsebnosti kovin ali/in prisotnosti Cu specij v obliki CuO v kalciniranih katalizatorjih. To ugotovitev bi bilo potrebno v nadaljevanju podrobneje raziskati.
Keywords: čiščenje odpadnih voda, napredni oksidacijski procesi, heterogena kataliza, katalizatorji na silikatnem nosilcu, glifosat, kumarin
Published in RUNG: 11.09.2024; Views: 1202; Downloads: 18
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4. Utilizing structurally disordered AlMg-oxide phase in Cu/ZnO catalyst for efficient ▫$CO_2$▫ hydrogenation to methanolAndraž Mavrič, Gregor Žerjav, Blaž Belec, Matevž Roškarič, Matjaž Finšgar, Albin Pintar, Matjaž Valant, 2023, published scientific conference contribution abstract Keywords: carbon dioxide, methanol, catalysis
Published in RUNG: 15.09.2023; Views: 2670; Downloads: 8
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5. 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: 3309; Downloads: 9
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6. 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: 3599; Downloads: 35
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7. Structural disorder of AlMg-oxide phase supporting Cu/ZnO catalyst improves efficiency and selectivity for ▫$CO_2$▫ hydrogenation to methanolAndraž Mavrič, Gregor Žerjav, Blaž Belec, Matevž Roškarič, Matjaž Finšgar, Albin Pintar, Matjaž Valant, 2023, original scientific article Abstract: The performance of the Cu/ZnO catalyst system with the AlMg-oxide phase is studied for CO2 hydrogenation to methanol. The catalyst is prepared by thermal treatment of the hydrotalcite phase containing intimately mixed metal cations in the hydroxide form. CuO in the presence of ZnO and disordered AlMg-oxide phase gets easily reduced to Cu during the hydrogenation reaction. Its catalytic activity at relatively low Cu metal content (∼14 at.%) remains stable during 100 hours on stream at 260 °C with constant space-time yield for methanol (∼1.8 gMeOH gcat−1 h−1) and high methanol selectivity (>85 %) The improved performance is attributed to the neutralization of surface acidity, increased number of weak basic sites in the disordered phase, and lower tendency for coke formation.
Keywords: carbon dioxide hydrogenation, heterogenous catalysis, methanol, reducibility
Published in RUNG: 02.06.2023; Views: 2417; Downloads: 23
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8. In-situ XAS study of catalytic N[sub]2O decomposition over CuO/CeO[sub]2 catalystsMaxim Zabilsky, Iztok Arčon, Petar Djinović, Elena Tchernychova, Albin Pintar, 2021, original scientific article Abstract: We performed in‐situ XAS study of N 2 O decomposition over CuO/CeO 2 catalysts. The Cu K‐edge and Ce L 3 ‐edge XANES and EXAFS analyses revealed the dynamic and crucial role of Cu 2+ /Cu + and Ce 4+ /Ce 3+ ionic pairs during the catalytic reaction. We observed the initial formation of reduced Cu + and Ce 3+ species during activation in helium atmosphere at 400 °C, while concentration of these species decreased significantly during steady‐state nitrous oxide degradation reaction (2500 ppm N 2 O in He at 400 °C). In‐situ EXAFS analysis further revealed a crucial role of copper‐ceria interface in this catalytic reaction. We observed dynamic changes in average number of Cu‐Ce scatters under reaction conditions, indicating an enlarging the interface between both copper and ceria phases, where electron and oxygen transfer occurs.
Keywords: in-situ XAS, Cu EXAFS, CuO/CeO2 nanorod catalys, N2O decomposition
Published in RUNG: 29.01.2021; Views: 4367; Downloads: 0
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9. In-situ XAS analysis of nanoshaped CuO/CeO2 catalysts used for N2O decompositionIztok Arčon, Maxim Zabilsky, Petar Djinović, Albin Pintar, 2018, published scientific conference contribution abstract Abstract: The goal of this research is to establish the working state and correlations between atomic structure and catalytic activity of nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction. The catalysts contained CuO nanoclusters dispersed over different CeO2 morphologies: nano-rods and nano-cubes. N2O is a side product of nitric and adipic acid production and a very potent greenhouse gas that is formed in amounts estimated at about 400 Mt/a of CO2 equivalent. Consequently, the development of robust, active and selective catalysts for N2O decomposition is of a great environmental and economical interest. CeO2-based materials promoted by CuO represent a new class of catalysts that exhibit considerable activity in N2O decomposition reaction between 300 and 500 °C [1-3], and are significantly cheaper and more efficient than Pt, Pd or Rh based catalysts.
In order to maximize the efficiency of the catalyst, the active site in this reaction needs to be identified and the mechanism clarified. In-situ Cu K-edge and Ce L3-edge XANES and EXAFS analysis was done on a set of CuO/CeO2 catalysts with different ceria morphology (nano-cubes, nano-rods) and Cu loadings between 2 to 8 wt. %, during N2O decomposition reaction, under controlled reaction conditions at 400 °C. The XAS spectra were measured in-situ, in a tubular reactor, filled with protective He atmosphere at 1 bar, first at RT, then during heating, and at final temperature of 400 °C, during catalytic reaction, when the catalyst was exposed to a small amount (0.2 vol%) of N2O mixed with He.
The Cu K-edge and Ce L3-edge XANES and EXAFS analysis reveals changes in valence and local structure of Cu and Ce in the CuO/CeO2 catalysts. In the initial state (in He at RT), copper is present in the form of CuO nanoparticles attached to the CeO2 surface. After heating in He to 400 °C, partial (10%) reduction of Ce [Ce(IV)→Ce(III)] is detected, significant part of Cu(II) is reduced to Cu(I) and Cu(0) species, and direct Cu-Cu bonds are formed. During catalytic N2O decomposition at 400°C, all Ce(III) is oxidized back to Ce(VI), and a major part of Cu is oxidized back to Cu(II), with about 5% of Cu(I) remaining in equilibrium state. Observed structural and valence changes of copper strongly depend on its loading and CeO2 morphology.
With systematic In-situ XAS analysis of different nanoshaped CuO/CeO2 catalysts, we identified the structural characteristics and changes of Cu and Ce phases during catalytic N2O decomposition reaction, which could lead to identification of the active catalytic site during the reaction and further improve the performance of these promising catalytic materials.
Keywords: EXAFS, CuO/CeO2 catalyst, N2O decomposition
Published in RUNG: 12.09.2018; Views: 5097; Downloads: 0
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10. Operando XAS analysis of CuO/SiO2 and CuO/CeO2 catalystsIztok Arčon, Janvit Teržan, Petar Djinović, Maxim Zabilsky, Albin Pintar, 2018, published scientific conference contribution abstract Abstract: The possibilities of the operando XAS analysis of catalysts will be presented on two case
studies of promising new catalytic materials: alkali doped nano-dispersed copper oxide
clusters on ordered mesoporous SiO2, which is highly active and selective towards propylene
epoxidation [1], and nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction [2].
Operando Cu K-edge and Ce L3-edge XANES and EXAFS analysis was performed during
catalytic reactions under controlled reaction conditions in a tubular reactor filled with
protective He atmosphere at 1 bar. The spectra were measured before the reaction at RT, then
during heating, and during catalytic reaction at 400 °C under controlled atmosphere.
Operando XANES analysis is used to monitor the changes in valence states and local
symmetries of Cu and Ce cations in the catalysts. A partial reduction of Cu2+ to Cu+ and Cu0
and Ce4+ to Ce3+ species was detected during catalyst activation, and re-oxidation during
catalytic reaction. Different dynamics of reaching a quasi-steady oxidation state were revealed
as the tested catalysts approached the quasi-steady state after 300 min of reaction.
Operando EXAFS spectra are used to precisely determine local structure of Cu and Ce
cations, to identify structural characteristics and changes of Cu and Ce species during the
catalytic reactions. In this way, the active site in the catalytic reactions can be identified and
the mechanism of the reaction clarified.
The results of operando XAS analyses are crucial to guide further material modification, to
obtain more effective catalyst, and material which is more resistant to inhibiting effects that
cause catalyst deactivation during catalytic reaction.
Keywords: katalizatorji, Cu XANES, EXAFS
Published in RUNG: 12.09.2018; Views: 4885; Downloads: 0
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