1. Protocol for the ex-situ electrochemical performance evaluation of the high-temperature pemfc electrodes : activity, durability and wettability inter-relationsRajan Ma Maurya, Per Morgen, Sašo Gyergyek, Shuang Ma Andersen, 2026, izvirni znanstveni članek Povzetek: Effect of pre-wetting on catalyst utilization and durability of high-temperature proton exchange membrane fuel cell (HT-PEMFC) gas diffusion electrodes (GDEs) was investigated in a three-electrode configuration. Pre-wetting protocols included treatment in ethanol-water mixture (0, 10, 50 and 100 % v/v ethanol), ethanol-water vapor and concentrated orthophosphoric acid (14.85 M) at 150 °C. All pre-wetting approaches significantly enhanced electrode wettability by reducing hydrophobicity and surface tension, leading to improved initial catalyst utilization. However, accelerated stress test (AST) revealed a trade-off between utilization and durability, with wetted electrodes exhibiting lower electrochemically active surface area (ECSA) and Pt retention compared to untreated electrodes. Changes in Pt crystallite and particle sizes during the AST were estimated through X-ray diffraction analysis and transmission electron microscopy. All three wetting procedures have similar effects on catalyst utilization and durability without compromising the structural integrity. Single-cell measurements showed that while pre-wetting is effective for rapid screening and improving the initial performance, its benefits are not directly transferable to practical operation without further optimization. These findings highlight the trade-off between catalyst utilization and durability in HT-PEMFC GDEs.
Ključne besede: electrocatalysts, accelerated stress test
Objavljeno v DiRROS: 16.06.2026; Ogledov: 80; Prenosov: 50
 Celotno besedilo (2,76 MB)
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2. Additive manufacturing of polymer-derived SiOC(Fe) ceramic composites as a catalyst support exhibiting magnetic heating capabilityMilan Vukšić, Thomas Konegger, Martin Schwentenwein, Sašo Gyergyek, Anja Sedminek, Sandra Drev, Marijan Nečemer, Andraž Kocjan, Aljaž Iveković, 2026, izvirni znanstveni članek Povzetek: Additive manufacturing (AM) of advanced functional ceramics using preceramic polymers (PCPs) is gaining attention due to its processability and tailorable properties. A photosensitive resin with iron-modified polysiloxanes was developed for vat photopolymerization (VPP) to create porous SiOC(Fe) catalytic supports with magnetic heating capability. Ferric acetylacetonate and ferrocene were examined as iron precursors, leading to the formation of Fe-based magnetic particles (α-Fe, Fe3C, FexSiy) within the silicon oxycarbide (SiOC) ceramic matrix after pyrolysis at 800 to 1500 °C. Depending on the Fe-based precursor used and the applied pyrolysis temperature, the obtained monoliths exhibited magnetic nanoparticle (MNP) contents ranging from 0.9 to 7.9 wt%, with particle sizes from 17 to 96 nm. The monolithic catalyst supports fabricated from ferric acetylacetonate modified PCP-based resin formulations, pyrolyzed at 900 °C, exhibited the highest specific absorption rate and resulted in magnetic heating up to 200 °C at an applied external magnetic field of 60 kA·m−1. While catalyst supports fabricated from ferrocene modified PCP-based resin formulations had lower heating capabilities, they offered better printability and higher ceramic yield. In situ formed MNPs impart magnetic properties advantageous for catalyst support heating, highlighting AM’s design flexibility and PCPs’ role in creating tailored, lightweight structures with controlled porosity.
Ključne besede: preceramic polymers, magnetic nanoparticles, ceramic nanocomposite, induction/magnetic heating, advanced functional ceramics
Objavljeno v DiRROS: 20.05.2026; Ogledov: 129; Prenosov: 125
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3. The synergetic effect of Cu+/Cu2+ in unsupported CuxO on the activity and mechanism of low-temperature CO oxidation : a transient kinetic and isotopic studyMichalis A. Vasiliades, Georgia-Maria D. Zarkou, Cheng Zhang, Alexandra Theodosiou, Mirko Prato, Sašo Gyergyek, Petar Djinović, Sotirios Christodoulou, Angelos M. Efstathiou, 2026, izvirni znanstveni članek Povzetek: This work has been motivated by the lack of knowledge concerning the influence of the surface Cu+/Cu2+ molar ratio on the composition and reactivity of the adsorbed phase established on the unsupported Cu2O-CuO solids during CO oxidation in excess oxygen (1% CO/20% O2/He) and at low temperatures (T < 200 °C). Variation of the Cu+/Cu2+ ratio was achieved under controlled calcination conditions applied on an initially c-Cu2O synthesized by the colloidal method. The influence of the Cu+/Cu2+ molar ratio on the mechanism of CO oxidation (Langmuir–Hinshelwood, Mars–van Krevelen, or Eley–Rideal), the surface concentration of active CO-s and COO-s reaction intermediates, and the thermal stability of carbonate-type adsorbed inactive species formed on the working catalytic surface were derived using the SSITKA technique combined with mass spectrometry and in situ DRIFTS. It was found that for high Cu+/Cu2+ molar ratio values (ca. ∼4.9), CO oxidation follows an Eley–Rideal mechanism, where gaseous CO reacts mainly with labile lattice oxygen species. Reversibly chemisorbed CO (θ ∼ 0.15) was measured, but this was not in the CO oxidation path. On the other hand, for low Cu+/Cu2+ molar ratio values (ca. 0.01–0.025), the mechanism shifts toward M-vK type, where the concentration of active COO-s was found to increase with increasing Cu2+/Cu+ molar ratio. Two types of linear adsorbed CO-s were identified by SSITKA-DRIFTS under working reaction conditions, and these were associated with Cu2+ and Cu+ sites. The ratio of the two adsorbed CO species did not vary proportionally with the Cu+/Cu2+ ratio. The specific CO oxidation rate (per gram or m2 of CuxO) was found to increase with increasing Cu+/Cu2+ ratio, while the opposite is true for the apparent activation energy (Eapp, kJ mol–1). An Eapp of 80 kJ mol–1 for Cu+/Cu2+ ∼ 4.9 compared to 125 kJ mol–1 for Cu+/Cu2+ ∼ 0.01 was measured. TOFCO (s–1) values were estimated based on the active sites associated with reaction intermediates truly participating in the CO oxidation reaction path. The TOFCO was also found to increase with increasing Cu+/Cu2+ ratio, largely due to the increased concentration of Cu2O-CuO heterojunctions of the hollow structure formed (Cu+/Cu2+ ∼ 4.9), and likely to their enhanced site activity. Dynamic rates of lattice oxygen reduced and its amount (He → 1%CO/He step-gas switch) and those for oxygen refilling (He → 2% O2/He step-gas switch) over the reduced Cu2O-CuO, the chemical structures of CO-s and CO2-s formed, and the thermal stability of CO2-s in the oxygen atmosphere were determined. HRTEM highlighted the morphology change of Cu2O particles with varying calcination temperature of c-Cu2O NPs. X-ray photoelectron spectroscopy allowed us to estimate the surface Cu+ and Cu2+ composition as a function of calcination temperature. In situ CO-DRIFTS enabled the examination of variations in the surface Cu+/Cu2+ ratio under the CO oxidation reaction conditions.
Ključne besede: SSITKA-CO oxidation, SSITKA-DRIFTS, CuxO, Cu2O-CuO, heterojunction redox dynamics in CuxO, CO oxidation mechanism, reduction of lattice oxygen by CO
Objavljeno v DiRROS: 30.03.2026; Ogledov: 367; Prenosov: 298
Celotno besedilo (7,00 MB)
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5. Dynamic and electrified ammonia synthesis enabled by magnetic heating of barium-promoted ruthenium catalystAnja Sedminek, Darko Makovec, Matej Huš, Anže Prašnikar, Stanislav S. Jakuškin, Blaž Likozar, Janvit Teržan, Sašo Gyergyek, 2026, izvirni znanstveni članek Ključne besede: magnetic heating, ammonia synthesis, barium promoted catalyst, electrification
Objavljeno v DiRROS: 25.03.2026; Ogledov: 318; Prenosov: 177
Celotno besedilo (5,82 MB)
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6. Mn-induced stabilization of a ▫$\beta$▫-alumina-type defect structure in barium hexaferrite nanoplateletsDarko Makovec, Matic Poberžnik, Janvit Teržan, Tomaž Mertelj, Damjan Vengust, Goran Dražić, Darja Lisjak, Sašo Gyergyek, 2026, izvirni znanstveni članek Povzetek: Hexaferrite nanoplatelets exhibit size-dependent structural variations influencing their magnetic properties. Here, we synthesized Mn-substituted barium ferrite nanoplatelets via hydrothermal methods, achieving up to ∼27% Fe substitution. Advanced STEM and Raman analyses revealed depletion of Fe(2b) trigonal lattice sites and associated oxygen vacancies, forming a β-alumina-type ferrite structure─representing the first pure Ba2+ β-ferrite analogue. First-principles modeling confirmed the thermodynamic stabilization of this defected structure at higher Mn/Fe ratios. Mn substitution reduced nanoplatelet size and suppressed magnetic properties, which were restored upon annealing at 800 °C, reverting to the M-type hexaferrite structure with expected magnetic behavior. These findings elucidate nanoscale structural adaptations induced by chemical substitution and offer insights into tailoring the magnetic properties of barium ferrite nanoplatelets through controlled synthesis and post-treatment.
Objavljeno v DiRROS: 23.03.2026; Ogledov: 239; Prenosov: 220
Celotno besedilo (11,07 MB)
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7. The effect of carbon support on rhenium-catalyzed glyceric acid deoxydehydration into biobased acrylic acidMaja Gabrič, Brigita Hočevar, Anej Blažič, Janvit Teržan, Sašo Gyergyek, Blaž Likozar, Miha Grilc, 2026, izvirni znanstveni članek Ključne besede: carbon support, bio-based acrylic acid, glyceric acid, deoxydehydration, rhenium oxides catalysts
Objavljeno v DiRROS: 02.02.2026; Ogledov: 435; Prenosov: 326
Celotno besedilo (3,44 MB)
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8. Hydrolysis synthesis of iridium oxide ▫$(IrO_x)$▫ on carbon for acidic oxygen evolution : influence of heat-treatment on structure and electrocatalytic activitySwapnil Sanjay Karade, Raghunandan Sharma, Sašo Gyergyek, Per Morgen, Bettina Pilgaard Andersen, Martin Aaskov Karlsen, Dorthe Ravnsbæk, Shuang Ma Andersen, 2026, izvirni znanstveni članek Povzetek: The development of efficient and durable oxygen evolution reaction (OER) electrocatalysts is critical for advancing proton exchange membrane water electrolyzers (PEMWEs). This study presents a nanostructured iridium oxide anchored on high-surface-area carbon (IrOx/C) OER electrocatalyst, synthesized through ultrasonication-assisted deposition of hydrolysis-derived colloidal IrOx nanoparticles onto the carbon support. The as-prepared IrOx/C exhibits a mass activity exceeding five times that of unsupported benchmark commercial IrO2, attributed to its uniform nanoparticle distribution and enhanced surface chemistry. Post-synthesis heat-treatments at two different temperatures (200 or 300 °C) were employed to stabilize the catalyst structure. Notably, the sample treated at 200 °C retained 84% of its initial activity after accelerated stress testing, outperforming the commercial counterpart, which retained 67 % under identical conditions. Comprehensive structural and morphological analyses revealed that the heat-treatment increased the IrOx particle size and decreased the Ir³⁺/Ir⁴⁺ ratio while leaving the amorphous nature of IrOx unaffected, which combinedly led to the improved durability. These findings offer valuable insights into designing stable low-iridium OER electrocatalysts for acidic PEMWE applications.
Ključne besede: iridium oxide, oxygen evolution reaction, carbon support, stability
Objavljeno v DiRROS: 15.01.2026; Ogledov: 502; Prenosov: 308
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9. Synthesis of a magnetically heatable ceria–supported ruthenium catalyst via deposition of nanocrystalline ceria on silica-coated magnetic iron–oxide nanoparticlesNina Kosi Križaj, Jakov-Stjepan Pavelić, Miha Grilc, Sašo Gyergyek, Darko Makovec, 2026, izvirni znanstveni članek Povzetek: We report the synthesis of a ceria-based catalyst support containing embedded magnetic iron–oxide nanoparticles (IONPs) that enable heating under a high-frequency alternating magnetic field. The ≈11 nm IONPs, synthesized by co-precipitation of Fe2+/Fe3+ ions at room temperature, were coarsened to ≈18 nm through subsequent hydrothermal treatment at 120 ◦C and then coated with a ≈2 nm silica layer. The catalyst support was prepared by depositing nanocrystalline ceria (CeO2) onto the IONPs via controlled precipitation of Ce3+ ions in the presence of hexamethylenetetramine (HMTA) in aqueous suspension. When deposited directly on the iron oxide, ceria formed small agglomerates of ≈10 nm octahedral nanocrystallites, whereas deposition on silicacoated IONPs produced a homogeneous 3–6 nm-thick shell composed of ≈3 nm globular crystallites. Special attention was given to elucidating the mechanism of shell formation. The magnetic catalyst was obtained by precipitating Ru nanoparticles (1–2 nm) onto the ceria support. Morpho-structural characterization was performed by XRD, TEM, and aberration-corrected STEM. Static and dynamic magnetization measurements at room temperature were used to assess the magnetic and heating performance. At low field amplitudes (<15 mT), catalysts prepared with IONPs of both sizes exhibited similar specific absorption rates, whereas at higher amplitudes the larger IONPs demonstrated superior heating efficiency. The catalytic performance was demonstrated in the magnetically heated hydrogenation of the bio-based compound 5-(hydroxymethyl)furfural to 2,5-bis (hydroxymethyl)furan, showing high activity, 100 % selectivity, and excellent stability upon recycling.
Ključne besede: nanotechnology, catalyst synthesis, ceria, magnetic nanoparticles, catalysis by magnetic heating, biomass valorisation, transmission electron microscopy
Objavljeno v DiRROS: 14.01.2026; Ogledov: 474; Prenosov: 303
Celotno besedilo (11,51 MB)
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