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1.
Astrotop_X : razstava
Nejc Trampuž, Dorotea Dolinšek, Peter Purg, Andreja Gomboc, 2024, razstava

Opis: Medtem ko je velik del vesoljske industrije pa tudi družbenih ambicij in pripovedi usmerjen na iskanje življenju prijaznega planeta, se skupina umetnic_kov in znanstvenic_kov v projektu Astrotop_X sprašuje, kdo ali kaj je (ali so) subjekt(i), ki išče(jo) drugi dom v vesolju in kaj določa dejavnike, ki kozmično krajino opredelijo kot krajino ‘B.’ Izbrani ekosistem v kapsuli s pomočjo senzorske tehnologije ter računalniškega algoritma upira pogled v globoko vesolje, brska po podatkovni bazi eksoplanetov in presoja, kam – in če sploh – bi se kazalo preseliti v prihodnosti. Skrbno izbran del kraškega ekosistema v kapsuli Astrotop_X preko sporočanja stanja temperature in cirkadialnega ritma v realnem času analizirala bivanjski potencial na eksoplanetih. Po premierni predstavitvi na pričujoči razstavi bo kapsula potovala v umetniško-znanstvenem laboratoriju xMobil, avtomobilski prikolici na sončne celice, ki predstavlja del zaprtokrožnega sistema, značilnega za vesoljska plovila. Tako se bodo v kapsuli naseljevali različni drugi prizadeti ekosistemi, medtem pa bodo teleskopi vsak dan odkrivali še kak morebitni planet B – ki pa bo seveda zmeraj predaleč, da bi tja tudi zares odpotovali ljudje. Morda pa bo to kdaj uspelo vsaj rastlinam? Z vidika botanike je kraško rastlinstvo nedvomno že prilagojeno na trde življenjske pogoje, navajeno je na stres: zimski mraz, padavine, sušo, pomanjkanje zemlje in pregrevanje tal, sončno sevanje, burjo. Podobno, najbrž še huje bi bilo na eksoplanetu. Moralno-ekološka dilema: ali ne bi bila takšna rastlina, ki obišče ali se preseli na tuj planet preprosto invazivna vrsta? Tehnični problem: kako naj rastline preživijo tako dolgo pot? Prav možnost preživetja v takih razmerah je izziv tudi za raziskovalce, zato je izbor rastlin za potovanje prva, morda najpomembnejša odločitev. Poleg živih rastlin bi v tako kapsulo lahko dodali tudi t.i. “semensko bombico” ki potrpežljivo čaka na konec medzvezdnega potovanja… Projekt Astrotop_X nasprotuje antropocentrističnemu dojemanju okolja in poudarja medsebojno soodvisnost vsega živega. V skladu z mislimi Donne Haraway in njenega “chthulucena” poziva k sobivanju večvrstnih skupnosti, kjer so nepremočrtna prepletenost in soodvisnost ključni za prihodnost Zemlje in njenih ekosistemov. Le na takšnem globokem sobivanju pa lahko temeljijo tudi tvorne spekulacije za prihodnost. Ali lahko rastline brez človeškega posredovanja postanejo zares avtonomni protagonisti medzvezdnih potovanj in Skupina Astrotop_X: Nejc Trampuž & Dorotea Dolinšek, umetnika Andreja Gomboc, astronomija (UNG FN / CAK) pETER Purg, znanost-umetnost (UNG FH/AU, GO! 2025) Sodelujejo: Programiranje: Saptashwa Bhattacharyya (UNG FN / CAK) Botanika: Jože Bavcon ter Blanka Ravnjak (Botanični vrt, UL BF) Tehnične rešitve: Dmitry Morozov Grafično oblikovanje: Nejc Trampuž Fotografiranje rastlin: Nejc Trampuž Asistent fotograf: Jure Gubanc Fotografija dogodkov: Gašper Rebernik (UNG AU) Ekologija: Peter Trontelj (UL BF) Skrb za jamo in okolje: Jamarski Klub Temnica Produkcija: GO! 2025, Xcenter, Mojca Stubelj Ars Astronomska opazovanja: Andrej Guštin, Eduardo Concepción Produkcija GO! 2025 (Mojca Stubelj Ars, Xcenter) v okviru projektov PostMobilnost in xMobil (pETER Purg) V sodelovanju z: Univerza v Novi Gorici (ung.si), Fakulteta za naravoslovje (FN), Fakulteta za humanistiko (FH), Akademija umetnosti (AU) Univerza v Ljubljani (uni-lj.si), Biotehniška fakulteta (BF) in Botanični vrt UL Zavod Cosmolab presežejo naše (človekove) fizične, fizikalne in nenazadnje geopolitične omejitve? V tem kontekstu Astrotop_X kritizira nenietzschejansko prečloveški tehnoeskapizem, ki poganja distopične fantazije kolonizacije vesolja. Opozarja na krhkost tuzemskih ekosistemov, ki so pogosto neupoštevani v dominantnih narativih o vesolju, tamkajšnjih vojaških in ekonomskih prestižih ter sci-fi pravljicah o lepi prihodnosti tam-nekje, vstran od grde in izčrpane krajine A. V algoritem kapsule je vključena podatkovna gesta, ki naposled priznava – da smo tukaj pravzaprav le ljudje (sami). Tudi rastline so večplastne in nomadske enote, zato opirajoč se na posthumanistično misel Rosi Braidotti Astrotop_x spodbuja premik izven človeškega subjekta, s tem pa na novo opredeljuje in v fokus postavlja voljo ne-človeških dejavnikov. Četudi skozi nemara vendarle prečloveški umetniško-znanstveni pristop, kapsula Astrotop_X omogoča, da narava sama postane aktivna raziskovalka kozmične prihodnosti, s čimer razbija hierarhično ločnico med človekom in ne-človekom. Poziva k preučevanju ne le našega vpliva na planet, temveč tudi, kako lahko (tudi močno prizadeti) ekosistemi kot je (pred kratkim od ognja opustošen) Kras sami navigirajo skozi kompleksne čezresničnosti, kjer Zemlja morda ni več edino ali primarno domovanje živih bitij.
Ključne besede: znanost-umetnost, intermedijski, antropocen, medijski, astronomija, botanika, ekologija, interdisiplinaren, vesoljsko potovanje
Objavljeno v RUNG: 11.11.2024; Ogledov: 446; Prenosov: 4
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Performance of copper - based catalysts for electrochemical CO2 reduction
Stefan Popović, 2023, doktorska disertacija

Opis: The industrial era has brought a never-ending problem to civilization through the emission of greenhouse gases (GHGs) while extracting energy from fossil fuels for a variety of processes. Among different GHGs, carbon dioxide (CO2) stood out as one of the most impactful and dangerous gases causing climatic disasters around the globe. However, CO2 as the abundant C1 building block, through the conversion pathways gives a plethora of opportunities to convert it into a wide range of commercial products and applications. The holistic approach among different conversion pathways is the electrochemical reduction of CO2 (eCO2R), ideally powered by renewable energy from intermittent sources such as wind and solar power. A silver bullet of the process is to find a catalyst that is active, selective, and stable. Copper has been recognized as the only monometallic catalyst that can produce products that require a transfer of >2e-. However, in recent years the increased awareness of its reconstructive nature under eCO2RR-relevant conditions multiplied the complexity of the parameters that can influence the reaction. Therefore overall thesis's approach to studying copper-based catalysts is based to understand the reconstructive aspect and the stability of Cu-based catalysts, and deeply comprehend their relationship with the activity/selectivity. Chapter 1 gives an introduction to the recent activities in the field of carbon capture, utilization and storage (CCSU) technologies, the fundaments of CO2 as a molecule, and its pathway toward state-of-the-art discoveries in the eCO2 R reaction. Afterward, the thesis focuses on the main experimental technique to produce nanostructured copper-based materials, namely, electrodeposition (Chapter 2). A big part of the thesis focuses on the establishment of an electrochemical setup for activity/selectivity measu rement. The setup consists of two parts: 1) construction of the custom-made gas-tight sandwich-type electrochemical cell and 2) optimization of the online gas and ex-situ liquid product detection. After the establishment of the reliable electrochemical setup, Chapter 3 focuses on electrochemically -grown Cu2O nanocubes catalyst and how the reconstructive nature induced by a particular electrochemical protocol influences on boost in activity/selectivity for methane production. The last part of the thesis consists contribution to the fundamental understanding of the degradation mechanisms and stability of Cu -based catalysts under eCO2RR conditions. A unique ex-situ approach, mirrored in identical location scanning electron microscopy (IL-SEM) method is employed to study electrodeposited spherical half-micron particles on the glassy carbon rotating disk electrode (GC-RDE). With this evidence, we could interpret the observed structural changes as two separate electrochemical processes occurring one after another, namely copper dissolution from pre-oxidized native nanoparticles and subsequent (electro -) redeposition of the dissolved copper species in a form of n ew smaller Cu fragments.
Ključne besede: electrocatalysts, electrochemical CO2 reduction, copper nanoparticles, IL-SEM, stability, degradation
Objavljeno v RUNG: 14.11.2023; Ogledov: 2459; Prenosov: 26
.pdf Celotno besedilo (5,55 MB)

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Efficiency of the grid energy storage technology based on iron-chloride material cycle
Uroš Luin, doktorska disertacija

Opis: Future high-capacity energy storage technologies are crucial for a highly renewable energy mix, and their mass deployment must rely on cheap and abundant materials, such as iron chloride. The iron chloride electrochemical cycle (ICEC), suitable for long-term grid energy storage using a redox potential change of Fe2+/Fe, involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial maximizing the energy efficiency of the electrolysis process. The thesis presents a study of the influence of electrolysis parameters on energy efficiency, performed in an industrial-type electrolyzer system. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency as a function of current density. The contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ±3 % was achieved using 2.5 mol dm-3 FeCl2 solution at 70 °C and a current density of 0.1 kA m-2. In terms of the energy input per Fe mass, this means 1.88 Wh g-1. The limiting energy input per mass of the Fe-deposit, calculated by extrapolating experimental results toward Eocell potential, was found to be 1.76 Wh g-1. For optimal long-duration electrolysis efficiency and performance, the optimal catholyte concentration range is 1-2 mol dm-3 FeCl2. We performed in situ X-ray absorption spectroscopy experimental studies to validate theoretical conclusions from literature related to the population and structure of Fe-species in the FeCl2 (aq) solution at different concentrations (1 - 4 mol dm-3) and temperatures (25 - 80 °C). This revealed that at low temperature and low FeCl2 concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five H2O at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical H2O is substituted by a Cl ion to yield a neutral Fe[Cl2(H2O)4]0. The transition from the charged Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well correlates with the existing state-of-the-art conductivity models. An additional steric impediment of the electrolytic cell is caused by the predominant neutral species present in the catholyte solution at high concentration. This correlates with poor electrolysis performance at a very high catholyte concentration (4 mol dm-3 FeCl2), especially at high current densities (> 1 kA m-2). The neutral Fe[Cl2(H2O)4]0 complex negatively affects the anion exchange membrane ion (Cl-) transfer and lowers the concentration of electroactive species (Fe[Cl(H2O)5]+) at the cathode surface. The kinetics of hydrogen evolution from the reaction between Fe powder and HCl acid was studied under the first-order reaction condition. The activation energy was determined to be 55.3 kJ mol-1.
Ključne besede: ICEC, Power-to-Solid, energy storage, hydrogen, ferrous chloride, electrolysis, Fe deposition, efficiency, XAS, structure and population, ionic species, ion association, conductivity
Objavljeno v RUNG: 18.04.2023; Ogledov: 2717; Prenosov: 44  (1 glas)
.pdf Celotno besedilo (4,34 MB)

6.
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, izvirni znanstveni članek

Opis: 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.
Ključne besede: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation
Objavljeno v RUNG: 04.01.2021; Ogledov: 3564; Prenosov: 0
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7.
Trajnostni potencial sončnih elektrarn v Sloveniji
Nejc Blažek, 2019, magistrsko delo

Opis: 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.
Ključne besede: sončna elektrarna, trajnostni potencial, analiza življenjskega cikla, obnovljivi viri energije
Objavljeno v RUNG: 19.12.2019; Ogledov: 9200; Prenosov: 175
.pdf Celotno besedilo (1,89 MB)

8.
Electrochemical dissolution of iridium and iridium oxide particles in acidic media : transmission electron microscopy, electrochemical flow cell coupled to inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy study
Primož Jovanovič, Nejc Hodnik, Francisco Ruiz-Zepeda, Iztok Arčon, Barbara Jozinović, Milena Zorko, Marjan Bele, Martin Šala, Vid Simon Šelih, Samo B. Hočevar, Miran Gaberšček, 2017, izvirni znanstveni članek

Opis: 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.
Ključne besede: Iridium Oxide Par-ticles, Electrochemical Dissolution of Iridium, Ir L3-edge XANES
Objavljeno v RUNG: 23.08.2017; Ogledov: 5078; Prenosov: 0
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9.
Presoja procesov oskrbne logistike v proizvodnji
Nejc Bensa, 2016, diplomsko delo

Ključne besede: Kanban, vlečni sistem, vitka proizvodnja, vitka logistika
Objavljeno v RUNG: 21.12.2016; Ogledov: 7148; Prenosov: 303
.pdf Celotno besedilo (2,26 MB)

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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, izvirni znanstveni članek

Opis: 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.
Ključne besede: ORR activity, fuel cells, platinum alloy, nanoparticle stability, intermetallic ordering, kinetic Monte Carlo, dealloying, in situ ICP-MS
Objavljeno v RUNG: 27.09.2016; Ogledov: 6775; Prenosov: 0
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