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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
Fulltext (3,27 MB)

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
Fulltext (6,36 MB)

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
Fulltext (1,89 MB)