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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, 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: 2148; 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: 1157; Downloads: 0
.pdf Fulltext (1,43 MB)

Ceramic synthesis of disordered lithium rich oxyfluoride materials
Jean-Marcel Ateba Mba, Iztok Arčon, Gregor Mali, Elena Tchernychova, Ralf Witte, Robert Kruk, Miran Gaberšček, Robert Dominko, 2020, original scientific article

Abstract: Disordered lithium-rich transition metal oxyfluorides with a general formula Li1þxMO2Fx (M being a transition metal) are gaining more attention due to their high specific capacity which can be delivered from the facecentered cubic (fcc) structure. The most common synthesis procedure involves use of mechanosynthesis. In this work, ceramic synthesis of lithium rich iron oxyfluoride and lithium rich titanium oxyfluoride are reported. Two ceramic synthesis routes are developed each leading to the different level of doping with Li and F and different levels of cationic disorder in the structure. Three different Li1þxMO2Fx samples (x ¼ 0.25, 0.3 and 1) are compared with a sample prepared by mechanochemical synthesis and non-doped LiFeO2 with fcc structure. The obtained lithium rich iron oxyfluoride are characterized by use of M€ossbauer spectroscopy, X-ray absorption spectroscopy, NMR and TEM. Successful incorporation of Li and F have been confirmed and specific capacity that can be obtained from the samples is in the correlation with the level of disorder introduced with doping, nevertheless oxidation state of iron in all samples is very similar. Conclusions obtained from lithium rich iron oxyfluoride are validated by lithium rich titanium oxyfluoride.
Found in: osebi
Keywords: Lithium batteries Face centered-cubic Oxyfluoride Li-rich Disorder
Published: 05.06.2020; Views: 210; Downloads: 0
.pdf Fulltext (2,37 MB)

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