Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme


11 - 15 / 15
First pagePrevious page12Next pageLast page
Atomically resolved dealloying of structurally ordered Pt nanoalloy as an oxygen reduction reaction electrocatalyst
Andraž Pavlišič, Primož Jovanovič, Vid Simon Šelih, Martin Šala, Marjan Bele, Goran Dražić, Iztok Arčon, Samo B. Hočevar, Anton Kokalj, Nejc Hodnik, Miran Gaberšček, original scientific article

Abstract: The positive effect of intermetallic ordering of platinum alloy nanoparticles on oxygen reduction reaction (ORR) activity has been well established. What is still missing is an understanding of selective leaching of the less noble metal from the ordered structure and its correlation to longterm ORR performance. Using a combination of kinetic Monte Carlo simulations and advanced characterization techniques, we provide unprecedented insight into dealloying of intermetallic PtCu3 nanoparticles a well-known binary alloy. Comparison of ordered and disordered samples with identical initial compositions and particle size distributions reveals an unexpected correlation: whereas the copper dealloying rates in the ordered and disordered counterparts are almost the same, in the ordered structure Pt atoms are surrounded by 15−30% more Cu atoms throughout all the stages of acid leaching. This more convenient Pt−Cu coordination explains the statistically significant increase of 23−37% in ORR activity of the ordered structure at all stages of alloy degradation.
Found in: osebi
Keywords: ORR activity, fuel cells, platinum alloy, nanoparticle stability, intermetallic ordering, kinetic Monte Carlo, dealloying, in situ ICP-MS
Published: 27.09.2016; Views: 4336; Downloads: 0
.pdf Fulltext (3,27 MB)

Electrochemical dissolution of iridium and iridium oxide particles in acidic media
Miran Gaberšček, Samo B. Hočevar, Vid Simon Šelih, Martin Šala, Marjan Bele, Milena Zorko, Barbara Jozinović, Iztok Arčon, Francisco Ruiz-Zepeda, Nejc Hodnik, Primož Jovanovič, 2017, original scientific article

Abstract: Iridium based particles as the most promising proton exchange membrane electrolyser electrocatalysts were investigated by transmission electron microscopy (TEM), and by coupling of electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometer (ICP-MS). Additionally, a thin-film rotating disc electrode (RDE), an identical location transmission and scanning electron microscopy (IL-TEM and IL-SEM) as well as an X-ray absorption spectroscopy (XAS) studies have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that iridium particles dissolved already well below oxygen evolution reaction (OER) potentials, presumably induced by iridium surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile type IrO2 particles (T-IrO2) are substantially more stable and less active in comparison to as prepared metallic (A-Ir) and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER relevant conditions E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyser.
Found in: osebi
Keywords: Iridium Oxide Par-ticles, Electrochemical Dissolution of Iridium, Ir L3-edge XANES
Published: 23.08.2017; Views: 2678; Downloads: 0
.pdf Fulltext (1,43 MB)

Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium Nanoparticles
Leonard Moriau, Marjan Bele, Živa Marinko, Francisco Ruiz-Zepeda, Gorazd Koderman, Martin Šala, Angelija Kjara Šurca, Janez Kovač, Iztok Arčon, Primož Jovanovič, Nejc Hodnik, Luka Suhadolnik, 2021, original scientific article

Abstract: The development of affordable, low-iridium-loading, scalable, active, and stable catalysts for the oxygen-evolution reaction (OER) is a requirement for the commercialization of proton-exchange membrane water electrolyzers (PEMWEs). However, the synthesis of high-performance OER catalysts with minimal use of the rare and expensive element Ir is very challenging and requires the identification of electrically conductive and stable high-surface-area support materials. We developed a synthesis procedure for the production of large quantities of a nanocomposite powder containing titanium oxynitride (TiONx) and Ir. The catalysts were synthesized with an anodic oxidation process followed by detachment, milling, thermal treatment, and the deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is the determining factor governing the catalyst’s OER activity and stability. Our study is supported by various state-of-the-art materials’ characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks as well as the Ir-supported samples on morphologically different TiONx from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen bubbles.
Found in: osebi
Keywords: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation
Published: 04.01.2021; Views: 1378; Downloads: 0
.pdf Fulltext (6,36 MB)

Presoja procesov oskrbne logistike v proizvodnji
Nejc Bensa, 2016, undergraduate thesis

Found in: osebi
Keywords: Kanban, vlečni sistem, vitka proizvodnja, vitka logistika
Published: 21.12.2016; Views: 4203; Downloads: 263
.pdf Fulltext (2,26 MB)

Trajnostni potencial sončnih elektrarn v Sloveniji
Nejc Blažek, 2019, master's thesis

Abstract: Proizvodnja električne energije s sončnimi elektrarnami v svetu in tudi v Sloveniji strmo narašča. Večina Slovencev ima do tovrstnega načina pridobivanja električne energije pozitiven odnos, k čemur je močno pripomogla Uredba o samooskrbi z električno energijo iz obnovljivih virov energije. Število novih sončnih elektrarn se bo povečevalo, s tem pa se bo v prihodnje povečevalo število izrabljenih solarnih panelov, ki jih sestavljajo silicijeve sončne celice. Z recikliranjem izrabljenih silicijevih sončnih celic lahko pridobimo do 85 % silicija oziroma 80 % sončnih celic za ponovno uporabo. Pri recikliranju tankoslojnih sončnih celic lahko vrnemo v proizvodni proces do 95 % polprevodnih materialov in do 90 % stekla. V povzetku analize življenjskega cikla (LCA) smo pokazali, v kakšnem obsegu je proizvodnja sončnih celic škodljiva za okolje ter kakšen je vpliv recikliranja le-teh ob koncu življenjske dobe za manjše onesnaževanje okolja in porabo virov. Pri ekonomskem vidiku trajnostnega potenciala smo z analizo treh različnih možnosti naložbe v samooskrbno sončno elektrarno prikazali finančni tok, ki ima v vseh treh možnostih vračilno dobo, krajšo od 10 let, in prihranke v družinskem proračunu tudi več kot 1.000 EUR na leto. Pokazali smo, da je nakup sončne elektrarne za samooskrbo z električno energijo ekonomsko upravičen, trajnosten in celo donosen. Analiza družbeno-socialnega vidika pokaže majhen vpliv na zaposlenost in dodano vrednost v Sloveniji, saj v Sloveniji obstaja le eno podjetje, ki proizvaja panele za sončne elektrarne. Pozitiven učinek na zaposlenost se kaže predvsem pri prodaji, upravljanju, servisu in montaži sončnih elektrarn. Izdelali smo analizo prednosti, slabosti, priložnosti in nevarnosti naložbe v sončno elektrarno ter jo primerjali z vetrno elektrarno.
Found in: osebi
Keywords: sončna elektrarna, trajnostni potencial, analiza življenjskega cikla, obnovljivi viri energije
Published: 19.12.2019; Views: 2876; Downloads: 103
.pdf Fulltext (1,89 MB)

Search done in 0 sec.
Back to top