10 results on '"Jovanovič, Primož"'
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2. Stability study of silver nanoparticles towards the halide electroreduction.
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Vanrenterghem, Bart, Jovanovič, Primož, Šala, Martin, Bele, Marjan, Šelih, Vid Simon, Hodnik, Nejc, and Breugelmans, Tom
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SILVER nanoparticles , *ELECTROLYTIC reduction , *HALIDES , *CHEMICAL stability , *ELECTROSYNTHESIS , *CATALYSTS - Abstract
Abstract The field of electrosynthesis has undergone a tremendous advancement in the past few decades by implementation of a catalyst at the nanoscale level. While significant knowledge on factors that influence the activity of specific reactions such as carbon-halogen (CX) bond activation has been gained, many questions regarding the stability and degradation of nanoparticles still remain unsolved. Through the combination of a three-folded advanced characterization approach that combines electrochemical, analytical and microscopic results we are for the first time able to map the degradation of nanoparticles for CX bond activation reaction. This methodology is exemplified on the stability study of the most active nanoparticles towards CX bond activation, namely Ag nanoparticles. Results indicate that under electrochemical operation conditions Ag nanoparticles degradation occurs via two mechanisms: (i) agglomeration/coalescence and (ii) electrochemical dissolution of nanoparticles in the electrolyte. Identification of these degradation mechanisms is a first step in the understanding and subsequently controlling the synthesis of active and sustainable catalyst towards industrial applications. [ABSTRACT FROM AUTHOR]
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- 2018
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3. Potentiodynamic dissolution study of PtRu/C electrocatalyst in the presence of methanol.
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Jovanovič, Primož, Šelih, Vid Simon, Šala, Martin, Hočevar, Samo, Ruiz-Zepeda, Francisco, Hodnik, Nejc, Bele, Marjan, and Gaberšček, Miran
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PLATINUM alloys , *DISSOLUTION (Chemistry) , *CARBON , *PLATINUM catalysts , *ELECTROCATALYSTS , *METHANOL - Abstract
Dissolution of PtRu alloy nanoparticles on carbon support in acidic environment is qualitatively and quantitatively investigated using an advanced electrochemical technique: electrochemical flow cell (EFC) on-line coupled to inductively coupled plasma mass spectrometer (ICP-MS). Profound insights into potential-resolved corrosion stability of Ru-Pt alloy in the potential window from 0.05 to 1.6 V vs RHE are obtained. Compared to pure Pt the PtRu alloy is less stable due to destabilisation of Pt surface caused by Ru dissolution together with the presence of weaker Ru-Pt bonds. However, at high potentials (1.5 and 1.6 V) Pt gets stabilised, presumably via a Ru catalysed oxygen evolution reaction that acts as a cathodic protection. Both Ru and Pt dissolution are enhanced in the presence of methanol due to consumption of surface ruthenium oxides, presumably Ru 2 O 3 , by the methanol oxidation reaction and an inhibited redeposition of Pt ions due to surface blockage of CO. The results may be used as useful guidelines in designing future DMFC and PEMFC catalysts. [ABSTRACT FROM AUTHOR]
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- 2016
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4. High-surface-area organic matrix tris(aza)pentacene supported platinum nanostructures as selective electrocatalyst for hydrogen oxidation/evolution reaction and suppressive for oxygen reduction reaction.
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Vélez Santa, John Fredy, Menart, Svit, Bele, Marjan, Ruiz-Zepeda, Francisco, Jovanovič, Primož, Jovanovski, Vasko, Šala, Martin, Smiljanić, Milutin, and Hodnik, Nejc
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CATALYSTS , *PLATINUM catalysts , *HYDROGEN oxidation , *OXYGEN evolution reactions , *OXYGEN reduction , *PENTACENE , *FUEL cells - Abstract
Developing a Pt-based electrocatalytic material able to selectively catalyze hydrogen oxidation (HOR) while supressing oxygen reduction (ORR) is beneficial for durability of the fuel cells. Namely, degradation of carbon supported Pt particles is dramatically influenced by the unwanted ORR enrolling at the anode due to the air penetration during start-up/shut-down events. We present an organic matrix tris(aza)pentacene (TAP), which belongs to π-functional materials with ladder-like conjugated nitrogen-containing units, as the support for Pt to form a "smart" fuel cell anode able to selectively catalyze HOR and to suppress ORR. "Switching-on/off" of the composite material activity is provided by reversible reduction/oxidation of the TAP in the low potential region which provokes TAP - H x TAP transition. Conductivity of the reduced H x TAP enables supported Pt particles to effectively run HOR. In contrast, restricted conductivity of oxidized TAP analogue leads to the substantial drop in the ORR activity with respect to benchmark Pt/C catalyst. Pt/TAP composite is able to selectively catalyze HOR/HER and to suppress ORR via adjustment of the TAP conductivity. Such selective electrocatalysis is of great importance for durability of Pt-based fuel cells catalysts. [Display omitted] • Pt nanostructures were grafted on high surface area tris(aza)pentacene (TAP) matrix. • Electrocatalytic activity of Pt/TAP composite for fuel cells reactions was studied. • Pt/TAP showed similar HOR/HER activity with respect to benchmark Pt/C catalyst. • ORR was significantly inhibited on Pt/TAP with respect to Pt/C. • Selective catalysis is provided by potential dependent tuning of TAP conductivity. [ABSTRACT FROM AUTHOR]
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- 2021
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5. CO-assisted ex-situ chemical activation of Pt-Cu/C oxygen reduction reaction electrocatalyst.
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Gatalo, Matija, Moriau, Leonard, Petek, Urša, Ruiz-Zepeda, Francisco, Šala, Martin, Grom, Matic, Galun, Timotej, Jovanovič, Primož, Pavlišič, Andraž, Bele, Marjan, Hodnik, Nejc, and Gaberšček, Miran
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TRANSITION metals , *ACTIVATION (Chemistry) , *PROTON exchange membrane fuel cells , *OXYGEN reduction , *ROTATING disk electrodes , *CARBON monoxide - Abstract
In the future, low-temperature proton exchange membrane fuel cells (PEMFC), together with batteries, are expected to compete and eventually replace conventional combustion engines in the automotive industry. Currently, the most promising strategy towards cost-effective and highly-active oxygen reduction reaction (ORR) electrocatalysts seems to be alloying of Pt with less expensive and less noble 3d transition metals (Cu, Co and Ni, ...). A crucial issue to be resolved in the near future is, however, to bridge the gap between the remarkable activities measured on the laboratory scale with thin film rotating disk electrode (TF-RDE) and the industrial membrane electrode assembly (MEA). In the case of Pt-Cu alloy, one of the major reasons for this difficulty is inadequate removal of unstable Cu or in other words, improper 'activation'. Inadequately removed Cu can act as an impurity by poisoning the Pt surface via the well-known underpotential deposition (UPD) interaction, resulting in the inhibition of ORR performance. Due to highly favourable experimental conditions, in-situ electrochemical activation (in-situ EA) in TF-RDE setup masks many of the issues one experiences when trying to do the same ex-situ. Thus, matching the ORR performance obtained after in-situ EA with ex-situ CA in the case of Pt-Cu system has not been properly addressed so far. Based on a deeper understanding of in-situ EA of our in-house designed Pt-Cu/C electrocatalyst we here demonstrate development of carbon monoxide (CO) assisted ex-situ CA method. By using this gram scale ex-situ CA method, we for the first time show that a Pt-Cu system can achieve very high ORR performances in TF-RDE setup without any need for the use of in-situ EA. Image 1 [ABSTRACT FROM AUTHOR]
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- 2019
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6. Correlating oxygen functionalities and electrochemical durability of carbon supports for electrocatalysts.
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Pavko, Luka, Gatalo, Matija, Đukić, Tina, Ruiz-Zepeda, Francisco, Surca, Angelja Kjara, Šala, Martin, Maselj, Nik, Jovanovič, Primož, Bele, Marjan, Finšgar, Matjaž, Genorio, Boštjan, Hodnik, Nejc, and Gaberšček, Miran
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PLATINUM nanoparticles , *CARBON-based materials , *X-ray photoelectron spectroscopy , *ELECTROCATALYSTS , *ELECTRIC batteries , *POLYELECTROLYTES , *CARBON-black , *CARBONACEOUS aerosols - Abstract
Achieving high durability of the polymer electrolyte membrane (PEM) fuel cell catalysts remains a major challenge. While most of the research focuses on the active phase, carbon support remains overlooked. In this study durability of carbon support materials for Pt alloy nanoparticles is critically evaluated. First graphene derivative (GD) based carbon supports with different chemical properties are prepared and utilized along with widely used commercial carbon black (CB) material. High-temperature electrochemical accelerated degradation tests (HT-ADTs) combined with X-ray photoelectron spectroscopy (XPS) show that the total amount of oxygen functionalities, the type of oxygen functionalities, and sp 2 carbon content play a crucial role in carbon support durability. The observations were confirmed with the direct online measurements of carbon corrosion via an advanced in-situ technique – an electrochemical cell coupled with a mass spectrometer (EC-MS). We report that increasing the content of sp 2 carbon and decreasing carboxyl functional groups have the most beneficial effect on stability. The study provides important guidelines for tailoring the carbon support properties and their relationship to the durability of the electrocatalyst, which could be crucial for producing more stable catalysts and achieving the Department of Energy's fuel cell system lifetime targets. Moreover, the innovative carbon design approach presented here could be applied in other fields such as batteries, supercapacitors, sensors and others. [Display omitted] • Graphene derivative support is more stable than carbon black support. • Oxygen functionalities and sp 2 carbon content in carbon support affect durability. • In-situ measurements using EC-MS confirm degradation of carbon support. • Findings offer carbon design relevant to batteries, supercapacitors, sensors and more. [ABSTRACT FROM AUTHOR]
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- 2023
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7. Intrinsic properties of nanoparticulate Ir-based catalysts for oxygen evolution reaction by AC voltammetry.
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Vodeb, Ožbej, Lončar, Anja, Bele, Marjan, Hrnjić, Armin, Jovanovič, Primož, Gaberšček, Miran, and Hodnik, Nejc
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OXYGEN evolution reactions , *CATALYSTS , *ACTIVATION energy , *HYDROGEN as fuel , *ELECTROCATALYSTS - Abstract
Water splitting in acidic media is a sustainable and efficient new way to produce hydrogen fuel. However, the main bottleneck preventing the wider use of electrolyzers is still the oxygen evolution reaction (OER). Currently, the best electrocatalysts for OER are Ir-based materials, but the mechanistic details are still not fully understood. In this work, we investigate the similarities and differences in the OER mechanism of three different Ir-based catalysts, namely Vulcan carbon-supported and unsupported metallic Ir and rutile IrO 2 nanoparticles, and the process of Ir activation. For this purpose, we use large amplitude AC Voltammetry to distinguish between capacitive and faradaic processes. To quantify the data, we also use a mechanistic fit of the resolved harmonics. We show that all catalysts share the same OER mechanism but require different amounts of activation cycles. We have found three intrinsic properties, which can adequately describe a material for electrocatalysis. First is the activation threshold number (ATN), second is the current normalized to the number of active sites (intrinsic current), and lastly the mass normalized active site density. It was found that Ir on Vulcan has an intrinsic activity at least 3 times higher than the other two materials under consideration, as well as having the highest active site density. From the model fits we can also gain further insight into the mechanistic details for each material. For metallic Ir samples, the rate-limiting step is shown to be water adsorption, whereas for IrO 2 the bottleneck is the inherently slower kinetics. This also indicates that IrO 2 does not produce the same IrOH as Ir metal and therefore has different intrinsic properties. This study provides new insights into the intrinsic properties of different Ir nanocatalysts and highlights a general approach to studying the reaction mechanisms and intrinsic properties of electrocatalysts. [ABSTRACT FROM AUTHOR]
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- 2023
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8. Atomically-resolved structural changes of ceramic supported nanoparticulate oxygen evolution reaction Ir catalyst.
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Koderman Podboršek, Gorazd, Kamšek, Ana Rebeka, Lončar, Anja, Bele, Marjan, Suhadolnik, Luka, Jovanovič, Primož, and Hodnik, Nejc
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OXYGEN evolution reactions , *SCANNING transmission electron microscopy , *CATALYSTS , *CERAMIC materials , *CERAMICS , *COMPUTER algorithms - Abstract
• Advanced identical location TEM was applied to TiON-supported Ir nanoparticles. • Efficient control over bubble accumulation during stability test was achieved. • Surface roughening revealed as the predominant degradation mechanism. • Oxidation suppression of ceramic-supported Ir was confirmed. The reduction of Ir loading and thus its efficient utilization in proton exchange membrane water electrolyzers (PEM-WE) inevitably depends on the rational design of novel nanomaterials. This, however, is not possible without the understanding of structure-stability interrelations and underlying mechanisms. When pursuing the reduction of Ir amount by its dispersion on ceramic materials, the interactions between the catalytically active sites and their support further complicate the already understood processes. In the present study, we use our unique approach, where we employ an Ir/TiON-based TEM grid and use it as a support system for the investigation of structural transformations of Ir nanoparticles. This was achieved by utilizing both the modified floating electrode (MFE) apparatus, which enables efficient bubble management during electrochemical experiments and identical-location scanning transmission electron microscopy (IL-STEM) approach. The analysis of obtained high-resolution images with in-house developed computer algorithms for image analysis reveals several processes with surface roughening being the predominant degradation mechanism. Additionally, suppressed oxidation tendency of supported Ir was directly confirmed. [Display omitted] [ABSTRACT FROM AUTHOR]
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- 2022
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9. Corrigendum to "Observing, tracking and analysing electrochemically induced atomic-scale structural changes of an individual Pt-Co nanoparticle as a fuel cell electrocatalyst by combining modified floating electrode and identical location electron microscopy" [Electrochimica Acta 388 (2021) 138513]
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Hrnjic, Armin, Kamšek, Ana Rebeka, Pavlišič, Andraž, Šala, Martin, Bele, Marjan, Moriau, Leonard, Gatalo, Matija, Ruiz-Zepeda, Francisco, Jovanovič, Primož, and Hodnik, Nejc
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CATALYSTS , *ELECTRONS , *ELECTRODES - Published
- 2022
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10. Observing, tracking and analysing electrochemically induced atomic-scale structural changes of an individual Pt-Co nanoparticle as a fuel cell electrocatalyst by combining modified floating electrode and identical location electron microscopy.
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Hrnjic, Armin, Kamšek, Ana Rebeka, Pavlišič, Andraž, Šala, Martin, Bele, Marjan, Moriau, Leonard, Gatalo, Matija, Ruiz-Zepeda, Francisco, Jovanovič, Primož, and Hodnik, Nejc
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PROTON exchange membrane fuel cells , *ELECTROCATALYSTS , *ELECTRON microscopy , *FUEL cells , *TRANSMISSION electron microscopy , *PLATINUM catalysts , *ELECTRODES - Abstract
Upon exposure to an electrochemical environment, structural properties of nanoparticulate electrocatalysts at the atomic scale are not stagnant but rather dynamic. These have a direct effect on catalysts' performance via structure-property relationships. The active surface structure is constantly changing via complex phenomena dependant on their nature and reaction conditions. State-of-the-art transmission electron microscopy (TEM) can already provide us with atomically precise structures of individual nanoparticles, which are a key to exploring structure-property relations. However, with the analysis of random nanoparticles with unknown structural history, it is impossible to realise the exact structural alternation mechanisms. In order to study these phenomena operando, in-situ or quasi-in-situ methods need to be developed and used. In the present study, we highlight a recently introduced methodological approach named modified floating electrode (MFE), which enables the assessment of (i) proton exchange membrane fuel cell (PEMFC) cathode oxygen reduction reaction (ORR) at the industry-relevant current densities and (ii) atomic-level structural changes of the same nanoparticle, via identical location scanning electron microscopy (SEM) and TEM approach (IL-SEM and IL-TEM), in one measurement. Careful analysis and comparison of atomically resolved high-resolution scanning TEM (HR-STEM) images of the same nanoparticle before and after MFE measurements were conducted via homemade microscopy image analysis algorithms. We reveal structural changes on the atomic-scale of the industrial benchmark Pt-Co nanoalloy ORR electrocatalyst upon exposure to electrochemical activation and high ORR current densities. Observing and comparing the detailed structure and morphology of the same nanoparticle reveals atomic-scale processes such as particle anisotropic etching and redeposition, besides other processes such as particle necking, anti-necking, pore formation, particle movement, coalescence, etc. The understanding of the dynamics behind these changes is crucial for the interpretation of ORR electrocatalyst's activity and stability. Our bottom-up approach enables direct investigation of nanoparticles' structure-stability relationships. [ABSTRACT FROM AUTHOR]
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- 2021
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