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Najdeno v: ključnih besedah
Povzetek najdenega: ...titanat, kisikova vrzel, Fe rob K EXAFS, XANES, disertacije, ...
Ključne besede: barijev titanat, kisikova vrzel, Fe rob K EXAFS, XANES, disertacije
Objavljeno: 22.01.2015; Ogledov: 5059; Prenosov: 357
Polno besedilo (0,00 KB)
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Najdeno v: ključnih besedah
Povzetek najdenega: ...sol-gel method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic activity...
Ključne besede: sol-gel method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic activity
Objavljeno: 15.02.2016; Ogledov: 4224; Prenosov: 0
Polno besedilo (131,22 KB)

Opis: Calcium batteries represent a promising alternative to lithium metal systems. The combination of the low redox potential and low cost and the energy-dense calcium anode (2073 mAh/cm3, similar to 2044 mAh/cm3 for Li) with appropriate low-cost cathode materials such as sulfur could produce a game-changing technology in several fields of applications. In this work, we present the reversible activity of a proof-of-concept Ca/S battery at room temperature, characterized by a surprising medium-term cycling stability with low polarization, promoted by the use of a simple positive electrode made of sulfur supported on an activated carbon cloth scaffold, and a state-of-the-art fluorinated alkoxyborate-based electrolyte. Insights into the electrochemical mechanism governing the chemistry of the Ca/S system were obtained for the first time by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The mechanism implies the formation of different types of soluble polysulfide species during both charge and discharge at room temperature, and the formation of solid CaS at the end of discharge. The reversible electrochemical activity is proven by the reformation of elemental sulfur at the end of the following charge. These promising results open the way to the comprehension of emerging Ca/S systems, which may represent a valid alternative to Mg/S and Li/S batteries.
Najdeno v: ključnih besedah
Ključne besede: Calcium/Sulfur Batteries EXAFS, XANES
Objavljeno: 17.10.2020; Ogledov: 2002; Prenosov: 0
Polno besedilo (3,74 MB)

Opis: In this study the uptake capacity of Mn(II) ions by zeolite A beads was investigated for different initial Mn concentration (100e400 mg Mn dm^-3) in batch mode at 25e55 C. The obtained adsorption capacity varying from 30 to 50 mg Mn g^-1 demonstrated a high affinity of zeolite A towards Mn(II) present in solutions. Kinetic studies indicated the intra-particle diffusion as the rate limiting step up to 45 C with apparent diffusivities in the range (1.2e2.0) x 10^-13 m2 s^-1 and the activation energy of 21.9 kJ mol^-1, which implies strong interactions between the zeolite A and Mn ions. At 55 C ion-exchange became the rate limiting step. The adsorption isotherms were studied at 25 C showing that the Mn adsorption is the best described by the Langmuir model suggesting a homogenous zeolite surface. XPS analysis of the Mnloaded beads showed that there is no surface accumulation of Mn but an almost uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of Mn(II) was followed by the Mn(II) oxidation and oxide formation. Regeneration of the spent zeolite was examined in 8 adsorption/desorption cycles by a chelating Na2EDTA in a fluidized column. It has been found that zeolite A beads could be reused for at least 4 cycles with satisfactory Mn(II) adsorption efficiencies of about 70%.
Najdeno v: ključnih besedah
Povzetek najdenega: ...uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of...
Ključne besede: Zeolite A Manganese Adsorption kinetics EXAFS/XANES XPS
Objavljeno: 01.04.2016; Ogledov: 4395; Prenosov: 0
Polno besedilo (1,27 MB)

Opis: Bacteria Klebsiella oxytoca (DSM 29614) secret a specific exopolysaccharide (EPS) in the presence of Fe(III)-citrate, as sole carbon and energy source, and produces after 7 days an iron gel precipitate (Fe-EPS) [1]. In the presence of palladium or other metal species, the culture of K. oxytoca can produce other mono or bimetal species (Pd-EPS, FePd-EPS) [2]. These bio-materials may be used as green biogenerated catalysts or for other biotechnological purposes. In this work we present the analysis of the morphology and the chemical state of the metals in mono and bi-metallic (Fe-EPS, Pd-EPS, FePd-EPS) complexes, by a combination of micro X-ray fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show that iron in monometallic Fe-EPS and bimetalic FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, as a mixture of different nano-crystalline iron oxides and hydroxides. Palladium on the other hand is found as Pd(0) in the form of metallic nanoparticles with fcc structure in both, bi-metallic (FePd-EPS) and mono-metallic (Pd-EPS) species. In bi-metallic species Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. Access to the SR facilities at ESRF (beamline ID21, project LS-2225), DESY (beamline C) Hamburg (project I-20110511 EC) and ELETTRA (beamline XAFS, project 20115112) is acknowledged.
Najdeno v: ključnih besedah
Povzetek najdenega: ...micro X-ray fluorescence, X-ray absorption spectroscopy methods ( XANES and EXAFS), and transmission electron microscopy. The...
Ključne besede: Klebsiella oxytoca, Fe, Pd, XANES, EXAFS, exopolysaccharide, FePd-EPS
Objavljeno: 28.06.2016; Ogledov: 4798; Prenosov: 0
Polno besedilo (388,27 KB)