| 1. |
- Dobrovetska, Oksana, et al.
(author)
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Electrocatalytic activity of Pd-Au nanoalloys during methanol oxidation reaction
- 2020
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In: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 45:7, s. 4444-4456
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Journal article (peer-reviewed)abstract
- Methanol fuel cells are very promising power source due to its high efficiency and low emissions of pollutants but their commercialization is hindered by development of the effective catalysts. Bimetallic nanostructured catalysts have been used to increase the effectiveness of methanol electrooxidation. Their high electrocatalytic activity can be accounted largely by the difference in electronegativity of two metals (e.g. Pd and Au), that resulting in gradual Auδ+→Auδ– transition with the increase in Pd content. Therefore, gold-enriched bimetallic Pd-Aunano were recommended as catalysts for oxidation processes since they are characterized by the presence of Auδ+ on their surface. Deposition of Pd, Au and Pd–Au nanoparticles (~50–350 nm) were carried out in dimethyl sulfoxide by pulsed mode of electrolysis directly on electrode surface. Cyclic voltammetry was the main method to study catalytic properties of the modified electrode in the anode oxidation process of methanol. It was found that oxidation rate on the electrode surface modified by bimetallic Pd–Au nanoparticles is ~1.5 times higher as compared to that in the case of electrodes modified by Pd or Au monometallic nanoparticles individually. In order to find highly active, selective, and stable catalysts for methanol electrocatalytic oxidation reaction additional studies are needed to understand the role of electrode surface charge and local OH− ions concentration from alkali solution.
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| 2. |
- Gosalawit-Utke, Rapee, et al.
(author)
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Nanoconfined 2LiBH(4)-MgH2 Prepared by Direct Melt Infiltration into Nanoporous Materials
- 2011
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:21, s. 10903-10910
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Journal article (peer-reviewed)abstract
- Nanoconfined 2LiBH(4)-MgH2 is prepared by direct melt infiltration of bulk 2LiBH(4)-MgH2 into an inert nanoporous resorcinol-formaldehyde carbon aerogel scaffold material. Scanning electron microscopy (SEM) micrographs and energy dispersive X-ray spectroscopy (EDS) mapping reveal homogeneous dispersion of Mg (from MgH2) and B (from LiBH4) inside the carbon aerogel scaffold. Moreover, nanoconfinement of LiBH4 in the carbon aerogel scaffold is confirmed by differential scanning calorimetry (DSC). The hydrogen desorption kinetics of the nanoconfined 2LiBH(4)-MgH2 is significantly improved as compared to bulk 2LiBH(4)-MgH2. For instance, the nanoconfined 2LiBH(4)-MgH2 releases 90% of the total hydrogen storage capacity within 90 mm, whereas the bulk material releases only 34% (at T = 425 degrees C and p(H-2) = 3.4 bar). A reversible gravimetric hydrogen storage capacity of 10.8 wt % H-2, calculated with respect to the metal hydride content, is preserved over four hydrogen release and uptake cycles.
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| 3. |
- Ischenko, Olena V., et al.
(author)
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Methanation of CO2 on bulk Co-Fe catalysts
- 2021
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In: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 46:76, s. 37860-37871
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Journal article (peer-reviewed)abstract
- The efficiency of CO2 methanation was estimated through gas chromatography in the presence of Co–Fe catalysts. Scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy were applied for ex-situ analysis of the catalysts after their test in the methanation reaction. Thermal programmed desorption mass spectroscopy experiments were performed to identify gaseous species adsorbed at the catalyst surface. Based on the experimental results, surface reaction model of CO2 methanation on Co–Fe catalysts was proposed to specify active ensemble of metallic atoms at the catalyst surface, orientation of adsorbed CO2 molecule on the ensemble and detailed reaction mechanism of CO2→CH4 conversion. The reaction step when OH group in the FeOOH complex recombined with the H atom adsorbed at the active ensemble to form H2O molecule was considered as the rate-limiting step.
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| 4. |
- Polido Legaria, Elizabeth, et al.
(author)
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Coordination of rare earth element cations on the surface of silica-derived nanoadsorbents
- 2018
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In: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 47:4, s. 1312-1320
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Journal article (peer-reviewed)abstract
- Silica (SiO2)-derived nanoadsorbents are a powerful and attractive tool for the extraction and separation of rare earth elements (REE) from many perspectives such as reusability, efficiency and minimum impact on the environment. In the present work, we investigated two different methods of adsorption down to the molecular level: (1) the mechanism of the coordination of different groups of REE (light, medium, heavy) with iminodiacetic acid (IDA) was revealed by exploiting models obtained from X-ray crystallography, explaining the selectivity of this type of ligand, and (2) the mechanism of the seeding of RE(OH)(3) initiated by SiO2-based nanoadsorbents was investigated by EXAFS, both individually and in combination with mechanism (1), showing the coexistence of both mechanisms. The REE loaded nanoadsorbents possess a high magnetic susceptibility. This property was studied by magnetometry to quantify the REE adsorption efficiency and compared with the values obtained from complexometry.
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| 5. |
- Saldan, Ivan
(author)
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Decomposition and formation of magnesium borohydride
- 2016
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In: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 41, s. 11201-11224
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Research review (peer-reviewed)abstract
- Nowadays, among all known borohydrides magnesium borohydride, Mg(BH4)(2), is the only one that demonstrates a partial reversible hydrogen sorption in moderate conditions. This is a clear reason why composites based on Mg(BH4)(2) are extensively studied fundamentally and are applicable as hydrogen storage materials. The review summarizes the main challenges still present for Mg(BH4)(2) that are decomposition and formation providing for the practical use of hydrogen mobility. Some technological approaches to the development of nanocomposites based on Mg(BH4)(2) are considered and discussed. Profound conclusions and future application of nanocomposites in fuel cells and secondary batteries is the final item of the proposed work. (c) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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| 6. |
- Saldan, Ivan, et al.
(author)
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Hydrogen Sorption in the LiH-LiF-MgB2 System
- 2013
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:33, s. 17360-17366
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Journal article (peer-reviewed)abstract
- A composite material in the LiH-LiF-MgB2 system has been synthesized by high-energy ball milling. Some peaks in addition to that of the binary 2LiH-MgB2 and 2LiF-MgB2 systems are observed for the composite material by high-pressure differential scanning calorimetry (HP-DSC), indicating the formation of intermediate phases. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) performed at 60 bar of H-2 and 390 degrees C shows a superposition of both reaction pathways that are typical for 2LiH-MgB2 and 2LiF-MgB2. After hydrogen absorption of the LiH-LiF-MgB2 composite the vibrational modes of LiBH4 were observed by attenuated total reflection infrared (ATR-IR) spectroscopy. The F-19 MAS NMR spectrum of the LiF-LiBH4 sample after heat treatment in hydrogen is strongly dominated by the centerband and spinning sidebands from LiF; in addition, a low-intensity resonance, very similar to that of [BF4](-) ion, is identified.
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| 7. |
- Saldan, Ivan, et al.
(author)
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Surface analysis of nickel nanomaterials electrodeposited on graphite surface
- 2019
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In: Micro & Nano Letters. - : INST ENGINEERING TECHNOLOGY-IET. - 1750-0443. ; 14:12, s. 1233-1237
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Journal article (peer-reviewed)abstract
- Pure Nickel (Ni) and Nickel-Palladium (Ni-Pd) alloy were electrodeposited on graphite surface via pulse electrolysis in dimethyl sulfoxide in form of rods and nanoparticles with a diameter of similar to 100-350 and similar to 10-35 nm, respectively. X-ray photoelectron spectroscopy (XPS) spectra of Ni 2p(3/2) region for these nanomaterials suggests on their surface Ni2+ precursor while after Ar+ ion-etching metallic nickel starts to be dominated. Both Pd-0 and Pd2+ for XPS spectra of Pd 3d(5/2) and 3d(3/2) were observed after electrodeposition. Scanning electron microscope-energy dispersive X-ray and XPS analysis confirmed electrodeposition of nickel nanomaterials in non-aqueous electrolyte. Using a lower concentration of Ni2+ precursor, nanoparticles with an average particle size of similar to 10-23 nm were prepared on a graphite surface.
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