1. Non-oxidative calcination enhances the methane dry reforming performance of ▫$Ni/CeO_{2−x}$▫ catalysts under thermal and photo-thermal conditionsKristijan Lorber, Vasyl Shvalya, Janez Zavašnik, Damjan Vengust, Iztok Arčon, Matej Huš, Andraž Pavlišič, Janvit Teržan, Uroš Cvelbar, Blaž Likozar, Petar Djinović, 2024, original scientific article Abstract: We analyzed the effect of the calcination atmosphere and visible-light contribution to an accelerated
reaction rate and improved H2 selectivity over 2 wt% Ni/CeO2−x nanorod catalysts. Spectroscopic and
structural characterization was performed by operando DRIFTS, in situ Raman, UV-vis and XAS
techniques, which were complemented by DFT calculations. Calcination in an argon or H2 atmosphere
yields 15% more active catalysts in the thermally driven reaction, which are also more susceptible to
light-induced rate acceleration compared to the catalyst calcined in air. The most active 2Ni/CeO2
catalyst calcined in hydrogen converts methane with a rate of 7.5 mmol (gcat min)−1 and produces a H2/
CO ratio of 0.6 at 460 °C when stimulated by a combination of visible light and thermal energy. In the
absence of visible light illumination and at an identical catalyst temperature, the achieved methane rate
was 4.2 mmol (gcat min)−1 and the H2/CO ratio was 0.49. The non-oxidative calcination improves nickel
dispersion and the formation of subnanometer sized Ni clusters, together with a higher abundance of
surface and bulk oxygen vacancies in ceria nanorods. The Ni–Ov–Ce3+components constitute the
catalytically active sites under visible light illumination, which enable the DRM reaction to proceed with
an Ea value of 20 kJ mol−1. Visible light also induces the following changes in the 2Ni/CeO2−x catalyst
during the DRM reaction: (1) decomposition and desorption of carbonates from the nickel–ceria
interface sites, (2) reduced population of nickel surface with carbonyl species and (3) promoted
adsorption and dissociation of methane.
Keywords: methane dry reforming performance, calcination
Published in RUNG: 05.07.2024; Views: 284; Downloads: 6
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2. CO[sub]2 activation over nanoshaped CeO[sub]2 decorated with nickel for low-temperature methane dry reformingKristijan Lorber, Janez Zavašnik, Iztok Arčon, Matej Huš, Janvit Teržan, Blaž Likozar, Petar Djinović, original scientific article Abstract: Dry reforming of methane (DRM) is a promising way to
convert methane and carbon dioxide into H2 and CO (syngas). CeO2
nanorods, nanocubes, and nanospheres were decorated with 1−4 wt % Ni.
The materials were structurally characterized using TEM and in situ
XANES/EXAFS. The CO2 activation was analyzed by DFT and
temperature-programmed techniques combined with MS-DRIFTS. Synthesized CeO2 morphologies expose {111} and {100} terminating facets,
varying the strength of the CO2 interaction and redox properties, which
influence the CO2 activation. Temperature-programmed CO2 DRIFTS
analysis revealed that under hydrogen-lean conditions mono- and bidentate
carbonates are hydrogenated to formate intermediates, which decompose
to H2O and CO. In excess hydrogen, methane is the preferred reaction
product. The CeO2 cubes favor the formation of a polydentate carbonate
species, which is an inert spectator during DRM at 500 °C. Polydentate covers a considerable fraction of ceria’s surface, resulting in
less-abundant surface sites for CO2 dissociation
Keywords: surface carbonates, in situ characterization, Ni XANES, Ni EXAFS, spectator species, CeO2 nanoshapes, CO2 activation
Published in RUNG: 13.07.2022; Views: 1855; Downloads: 0
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3. Electrochemical immunosensor functionalized with nanobodies for the detection of the toxic microalgae Alexandrium minutum using glassy carbon electrode modified with gold nanoparticlesSandra Oloketuyi, Elisa Mazzega, Janez Zavašnik, Kingkan Pungjunun, Kurt Kalcher, Ario De Marco, Eda Mehmeti, 2020, original scientific article Keywords: biosensors, toxic microalgae, nanobodies, impedance
Published in RUNG: 07.02.2020; Views: 3607; Downloads: 0
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