Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme

Options:
  Reset


11 - 20 / 23
First pagePrevious page123Next pageLast page
11.
Solvothermal synthesis of iron phosphides and their application for efficient electrocatalytic hydrogen evolution
Saim Emin, Takwa Chouki, Manel Machreki, 2020, original scientific article

Abstract: Abstract In this paper, we present a solvothermal synthesis of iron phosphide electrocatalysts using a triphenylphosphine (TPP) precursor. The synthetic protocol generates Fe2P phase at 300 °C and FeP phase at 350 °C. To enhance the catalytic activities of obtained iron phosphide particles heat-treatments were carried out at elevated temperatures. Annealing at 500 °C under reductive atmosphere induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500 °C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500 °C). Pure Fe2P films was prepared under argon atmosphere at 450 °C (Fe2P−450 °C). The electrocatalytic activities of heat-treated Fe2P−450 °C, Fe3P−500 °C, and Fe2P/FeP−500 °C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M H2SO4. The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest electrode potential of 110 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2 was achieved with Fe2P/FeP−500 °C catalyst.
Found in: ključnih besedah
Keywords: Solvothermal synthesis, Iron phosphide, Electrocatalyst, Hydrogen evolution, Overpotential
Published: 20.07.2020; Views: 1421; Downloads: 0
.pdf Fulltext (2,52 MB)

12.
13.
Synthesis of efficient iron phosphide catalyst for electrocatalytic hydrogen generation
Takwa Chouki, D. Lazarević, B. Donkova, Saim Emin, 2021, original scientific article

Abstract: A solvothermal synthesis of iron phosphide electrocatalysts using triphenylphosphine (TPP) as phosphorus precursor is presented. The synthetic protocol generates Fe2P/FeP phase at 350°C. After deposition of the catalyst onto graphite substrate heat-treatment at higher temperature was carried out. Annealing at 500°C under reductive atmosphere induced structural changes in the Fe2P/FeP samples which yielded a pure Fe2P phase. The electrocatalytic activity of the Fe2P catalyst was studied for hydrogen evolution reaction (HER) in 0.5 M H2SO4. The recorded overpotential for HER was about 130 mV vs. a reversible hydrogen electrode (RHE) at 10 mA cm−2
Found in: ključnih besedah
Keywords: solvothermal synthesis, iron phosphide, electrocatalyst, hydrogen evolution
Published: 10.05.2021; Views: 910; Downloads: 0
.pdf Fulltext (807,89 KB)

14.
Solvothermal synthesis of iron phosphides and their application for efficient electrocatalytic hydrogen evolution
Saim Emin, Manel Machreki, Takwa Chouki, 2020, published scientific conference contribution abstract

Abstract: We report the solvothermal synthesis of iron phosphide electrocatalysts using a low-cost phosphorus precursor [1]. The synthetic protocol allows for the preparation of a Fe2P phase at 300°C and FeP phase at 350°C. To enhance the catalytic activities of obtained iron phosphide particles, heat-treatments were carried out at elevated temperatures. Annealing at 500°C induced structural changes in the samples: (i) Fe2P provided a pure Fe3P phase (Fe3P−500°C) and (ii) FeP transformed into a mixture of iron phosphide phases (Fe2P/FeP−500°C). The electrocatalytic activities of heat-treated Fe2P−450°C, Fe3P−500°C, and Fe2P/FeP−500°C catalysts were studied for hydrogen evolution reaction (HER) in 0.5 M sulfuric acid (H2SO4). The HER activities of the iron phosphide catalyst were found to be phase dependent. The lowest recorded overpotential of 110 mV at 10 mA cm−2 vs. a reversible hydrogen electrode was achieved with Fe2P/FeP−500°C catalyst. The present approach allows the preparation of immobilized iron phsphide catalyst onto carbon support which is essential for application purpose. The procedure developed by us is an elegant approach to tune the composition of iron phosphide catalyst and control the morphology of particles.
Found in: ključnih besedah
Keywords: solvothermal synthesis, iron phosphide, electrocatalyst, hydrogen evolution, overpotential
Published: 13.05.2021; Views: 936; Downloads: 0
.pdf Fulltext (4,08 MB)

15.
Photo-Chemically-Deposited and Industrial Cu/ZnO/Al2O3 Catalyst Material Surface Structures During CO2 Hydrogenation to Methanol: EXAFS, XANES and XPS Analyses of Phases After Oxidation, Reduction, and Reaction
Blaž Likozar, Iztok Arčon, Venkata Dasireddy, Maja Pori, 2021, original scientific article

Abstract: Industrial Cu/ZnO/Al2O3 or novel rate catalysts, prepared with a photochemical deposition method, were studied under functional CH3OH synthesis conditions at the set temperature (T) range of 240–350 °C, 20 bar pressure, and stoichiometric carbon dioxide/hydrogen composition. Analytical scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray adsorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods were systematically utilized to investigate the interfaces, measured local geometry, and chemical state electronics around the structured active sites of commercially available Cu/ZnO/Al2O3 material or synthesized Cu/ZnO. Processed Cu K-edge EXAFS analysis suggested that various Cu atom species, clusters, metallic fcc Cu, Cu oxides (Cu2O or CuO) and the Cu0.7Zn2 alloy with hexagonal crystalline particles are contained after testing. It was proposed that in addition to the model’s Cu surface area, the amount, ratio and dispersion of the mentioned bonded Cu compounds significantly influenced activity. Additionally, XPS revealed that carbon may be deposited on the commercial Cu/ZnO/Al2O3, forming the inactive carbide coating with Cu or/and Zn, which may be the cause of basicity’s severe deactivation during reactions. The selectivity to methanol decreased with increasing T, whereas more Cu0.7Zn2 inhibited the CO formation through reverse water–gas shift (RWGS) CO2 reduction.
Found in: ključnih besedah
Summary of found: ...deposition method, were studied under functional CH3OH synthesis conditions at the set temperature (T) range...
Keywords: CH3OH synthesis, Cu/ZnO-based catalyst, XPS, XANES, EXAFS analyses, Catalyst selectivity and activity
Published: 03.06.2021; Views: 990; Downloads: 0
.pdf Fulltext (3,98 MB)

16.
Resolving the dilemma of Fe-N-C catalysts by the selective synthesis of tetrapyrrolic active sites via an imprinting strategy
Tim-Patrick Fellinger, Beate Paulus, Miran Gaberšček, Francisco Ruiz-Zepeda, Friedrich Wagner, Burak Koyutürk, Iztok Arčon, Yan-Sheng Li, Jian Liang Low, Davide Menga, 2021, original scientific article

Abstract: Combining the abundance and inexpensiveness of their constituent elements with their atomic dispersion, atomically dispersed Fe−N−C catalysts represent the most promising alternative to precious-metal-based materials in proton exchange membrane (PEM) fuel cells. Due to the high temperatures involved in their synthesis and the sensitivity of Fe ions toward carbothermal reduction, current synthetic methods are intrinsically limited in type and amount of the desired, catalytically active Fe− N4 sites, and high active site densities have been out of reach (dilemma of Fe−N−C catalysts). We herein identify a paradigm change in the synthesis of Fe−N−C catalysts arising from the developments of other M−N−C single-atom catalysts. Supported by DFT calculations we propose fundamental principles for the synthesis of M−N−C materials. We further exploit the proposed principles in a novel synthetic strategy to surpass the dilemma of Fe−N−C catalysts. The selective formation of tetrapyrrolic Zn−N4 sites in a tailor-made Zn−N−C material is utilized as an active-site imprint for the preparation of a corresponding Fe−N−C catalyst. By successive low- and high-temperature ion exchange reactions, we obtain a phase-pure Fe−N−C catalyst, with a high loading of atomically dispersed Fe (>3 wt %). Moreover, the catalyst is entirely composed of tetrapyrrolic Fe−N4 sites. The density of tetrapyrrolic Fe−N4 sites is more than six times as high as for previously reported tetrapyrrolic single-site Fe−N−C fuel cell catalysts
Found in: ključnih besedah
Keywords: Fe-N-C catalysts, selective synthesis, tetrapyrrolic active sites, EXAFS, XANES, single atom, DFT
Published: 25.10.2021; Views: 685; Downloads: 22
URL Fulltext (0,00 KB)
This document has many files! More...

17.
Boron‑rich boron carbide from soot
Sankaranarayana Iyer Sankararaman, H. V. Saritha Devi, Mohanachandran Nair Sindhu Swapna, 2020, original scientific article

Abstract: Boron carbide is a promising super-hard semiconducting material for refractory applications ranging from the nuclear industry to spacecraft. The present work is the frst report of not only turning futile soot, containing carbon allotropes in varying composition, into boron-rich boron carbide (BC), but also developing it by a low-cost, low-temperature, and green synthesis method. The BC synthesised from gingelly oil soot is subjected to structural, morphological, and optical characterisations. The feld emission scanning electron microscope shows beautiful fower-like morphology, and the thermogravimetric analysis reveals the high-temperature stability of the sample synthesised. The Tauc plot of the sample indicates a 2.38 eV direct bandgap. The formation of BC and boron-rich carbide evidenced by X-ray difraction studies is confrmed through Raman and Fourier transform infrared spectroscopic signatures of B–C and C–B–C bonds. The fuorescence, power spectrum, and CIE analyses carried out suggest the blue light emission for excitation at 350 nm
Found in: ključnih besedah
Summary of found: ...it by a low-cost, low-temperature, and green synthesis method. The BC synthesised from gingelly oil...
Keywords: boron carbide, soot, carbon nanoparticle, refractory, allotropes, green synthesis
Published: 30.06.2022; Views: 87; Downloads: 0
.pdf Fulltext (1,11 MB)

18.
Natural precursor based hydrothermal synthesis of sodium carbide for reactor applications
SWAPNA MOHANACHANDRAN NAIR SINDHU, 2017, original scientific article

Abstract: Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.
Found in: ključnih besedah
Keywords: sodium carbide, pandanus, hydrothermal synthesis, porous materials
Published: 30.06.2022; Views: 117; Downloads: 0
.pdf Fulltext (2,57 MB)

19.
Boron carbide Nanowires from castor oil for optronic applications: A low-temperature greener approach
SWAPNA MOHANACHANDRAN NAIR SINDHU, 2021, original scientific article

Abstract: The development of one-dimensional nanostructures has revolutionized electronic and photonic industries because of their unique properties. The present paper reports the low-temperature green synthesis of boron carbide nanowires, of diameter 14 nm and length 2 lm, by the condensation method using castor oil as the carbon precursor. The nanowires synthesized exhibit beaded chain morphology, and bandgap energy of 2.08 eV revealed through the Tauc plot analysis. The structure of boron carbide nanowires is revealed by micro-Raman, Fourier transform infrared spectroscopic, and X-ray diffraction analyses. The thermogravimetric analysis of the sample reveals the excellent thermal stability. The photoluminescence study reveals the nanowire’s blue light emission capability under ultraviolet excitation, which is substantiated by the CIE plot suggesting its potential in photonic applications.
Found in: ključnih besedah
Summary of found: ...properties. The present paper reports the low-temperature green synthesis of boron carbide nanowires, of diameter 14 nm...
Keywords: Boron carbide, Nanowires, castor oil, green synthesis
Published: 04.07.2022; Views: 66; Downloads: 0
.pdf Fulltext (1,56 MB)

20.
Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications
V. Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, original scientific article

Abstract: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confrm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Found in: ključnih besedah
Summary of found: ...engineering. The work reports the low-temperature green synthesis of hafnium carbide (HfC) using rice four...
Keywords: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Published: 04.07.2022; Views: 69; Downloads: 0
.pdf Fulltext (1,50 MB)

Search done in 0 sec.
Back to top