scholarly journals Spinel to Rock-Salt Transformation in High Entropy Oxides with Li Incorporation

Electrochem ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 60-74 ◽  
Author(s):  
Junbo Wang ◽  
David Stenzel ◽  
Raheleh Azmi ◽  
Saleem Najib ◽  
Kai Wang ◽  
...  
Keyword(s):  
Rock Salt ◽  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Electrode Materials ◽  
Lithium Ion ◽  
Optical Emission ◽  
Attenuated Total Reflection ◽  
X Ray ◽  
High Entropy ◽  
Infinite Variety

High entropy oxides (HEOs) constitute a promising class of materials with possibly new and largely unexplored properties. The virtually infinite variety of compositions (multi-element approach) for a single-phase structure allows the tailoring of their physical properties and enables unprecedented materials design. Nevertheless, this level of versatility renders their characterization as well as the study of specific processes or reaction mechanisms challenging. In the present work, we report the structural and electrochemical behavior of different multi-cationic HEOs. Phase transformation from spinel to rock-salt was observed upon incorporation of monovalent Li+ ions, accompanied by partial oxidation of certain elements in the lattice. This transition was studied by X-ray diffraction, inductively coupled plasma-optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and attenuated total reflection infrared spectroscopy. In addition, the redox behavior was probed using cyclic voltammetry. Especially, the lithiated rock-salt structure HEOs were found to exhibit potential for usage as negative and positive electrode materials in rechargeable lithium-ion batteries.

scholarly journals Reactivity of Metakaolin in Alkaline Environment: Correlation of Results from Dissolution Experiments with XRD Quantifications

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2214
Author(s):  
Sebastian Scherb ◽  
Mathias Köberl ◽  
Nancy Beuntner ◽  
Karl-Christian Thienel ◽  
Jürgen Neubauer
Keyword(s):  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Systematic Investigation ◽  
Attenuated Total Reflection ◽  
Emission Spectrometry ◽  
Alkaline Solutions ◽  
X Ray ◽  
Inductively Coupled ◽  
Before And After ◽  
Congruent Dissolution

Systematic investigation of filtrates and filter residues resulting from a 24 h treatment of metakaolin in different alkaline solutions were performed. On filtered metakaolin particles, inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements reveal an enrichment of iron and titanium, which suggests an inhomogeneous distribution of these cations. Since the SiO2/Al2O3 ratio remains constant in all filter residues examined, the dissolution of the Si and Al monomers is congruent. Structural differences, identified by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) as a consequence of alkali uptake, influence the X-ray scattering contribution of metakaolin, and thus quantifications with the partial or no known crystal structure (PONKCS) method. This leads to deviations between the degree of reaction calculated from Si and Al solubility from filtrate and that quantified by quantitative powder X-ray diffraction (QPXRD) using the filter residue. Nevertheless, the described changes do not cause a shift in the X-ray amorphous hump in case of congruent dissolution, and thus allow the quantification of the metakaolin before and after dissolution with the same hkl-phase model.

scholarly journals Microwave Assisted Novel Efficient Pd-free Catalyst for Suzuki C-C Coupling Reaction

2018 ◽  
Author(s):  
Ghalia Alzhrani ◽  
Nesreen Ahmed ◽  
Elham Aazam ◽  
Mohamed Mokhtar
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Coupling Reaction ◽  
Optical Emission ◽  
Nickel Catalysts ◽  
Aryl Halides ◽  
Precipitation Method ◽  
Coupling Reactions ◽  
Nickel Ions ◽  
X Ray

Suzuki cross-coupling reaction has developed one of the furthermost effectual approaches for the synthesis of biaryls or substituted aromatic moieties from aryl halides and arylboronic acids with a palladium-catalyst in the past two era’s. Herein, Pd-free layered double hydroxide containing nickel catalysts were prepared by co-precipitation method under ultrasonic irradiation and N2 atmosphere with different molar ratios of Ni: Mg: Al and coded as (1NiLDHs-Dr), (1.5NiLDHs-Dr) and (2NiLDHs-Dr). A series of reduced catalysts under 5%H2/N2 at different temperatures were coded as 1NiLDHs-R200, 1.5NiLDHs-R200 and 2NiLDHs-R200. As-synthesized 2NiLDHs-Dr was the superlative catalyst when coupling different aryl halides with different boronic acids derivatives. Deep investigation of all catalysts was done using different techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES), x-ray photoelectron spectroscopy (XPS), powder x-ray diffraction (XRD), thermogravimetric analyses (TGA), Fourier transfer infrared (FTIR), scanning electron microscope (SEM) connected with energy dispersive x-ray (EDX) and N2-physisorption at -196 ℃. The results attained verified that ɑ-Ni(OH)2 was fashioned for 2NiLDHs-Dr catalyst and the enclosure of nickel ions in the cationic sheet of layered structure were responsible for the fascinating catalytic efficacy rather than the basic nature of material. The Ni-containing LDHs catalysts encourage forthcoming studies in Pd-free catalyzed C-C coupling reactions.

scholarly journals The Use of Lanthanum Ions and Chitosan for Boron Elimination from Aqueous Solutions

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 718 ◽  
Author(s):  
Joanna Kluczka ◽  
Gabriela Dudek ◽  
Alicja Kazek-Kęsik ◽  
Małgorzata Gnus ◽  
Maciej Krzywiecki ◽  
...  
Keyword(s):  
Boric Acid ◽  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
High Performance ◽  
Essential Element ◽  
Optical Emission ◽  
Maximum Adsorption Capacity ◽  
Hydroxyl Groups ◽  
Lanthanum Hydroxide ◽  
X Ray

Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained hydrogel (La-CTS) was used for the elimination of the excess of B(III) from modelling solutions. The reaction between boric acid and hydroxyl groups bound to the lanthanum coordinated by chitosan active centres was the preponderant mechanism of the bio-adsorption removal process. The results demonstrated that La-CTS removed boric acid from the aqueous solution more efficiently than either lanthanum hydroxide or native chitosan hydrogel, respectively. When the initial boron concentration was 100 mg/dm3, the maximum adsorption capacity of 11.1 ± 0.3 mg/g was achieved at pH 5 and the adsorption time of 24 h. The successful introduction of La(III) ions to the chitosan backbone was confirmed by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Due to its high-performance boron adsorption-desorption cycle and convenient form, La-CTS seems to be a promising bio-adsorbent for water treatment.

scholarly journals Microwave Assisted Novel Efficient Pd-free Catalyst for Suzuki C-C Coupling Reaction

2019 ◽  
Author(s):  
Ghalia Alzhrani ◽  
Nesreen Ahmed ◽  
Elham Aazam ◽  
Mohamed Mokhtar ◽  
Tamer Saleh
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Coupling Reaction ◽  
Optical Emission ◽  
Nickel Catalysts ◽  
Aryl Halides ◽  
Precipitation Method ◽  
Coupling Reactions ◽  
Nickel Ions ◽  
X Ray

Suzuki cross-coupling reaction has developed one of the furthermost effectual approaches for the synthesis of biaryls or substituted aromatic moieties from aryl halides and arylboronic acids with a palladium-catalyst in the past two era’s. Herein, Pd-free layered double hydroxide containing nickel catalysts were prepared by co-precipitation method under ultrasonic irradiation and N2 atmosphere with different molar ratios of Ni: Mg: Al and coded as (1NiLDHs-Dr), (1.5NiLDHs-Dr) and (2NiLDHs-Dr). A series of reduced catalysts under 5%H2/N2 at different temperatures were coded as 1NiLDHs-R200, 1.5NiLDHs-R200 and 2NiLDHs-R200. As-synthesized 2NiLDHs-Dr was the superlative catalyst when coupling different aryl halides with different boronic acids derivatives. Deep investigation of all catalysts was done using different techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES), x-ray photoelectron spectroscopy (XPS), powder x-ray diffraction (XRD), thermogravimetric analyses (TGA), Fourier transfer infrared (FTIR), scanning electron microscope (SEM) connected with energy dispersive x-ray (EDX) and N2-physisorption at -196 ℃. The results attained verified that ɑ-Ni(OH)2 was fashioned for 2NiLDHs-Dr catalyst and the enclosure of nickel ions in the cationic sheet of layered structure were responsible for the fascinating catalytic efficacy rather than the basic nature of material. The Ni-containing LDHs catalysts encourage forthcoming studies in Pd-free catalyzed C-C coupling reactions.

Diatoms – A “Green” Way to Biosynthesize Gold-Silica Nanocomposites?

2018 ◽  
Vol 232 (9-11) ◽  
pp. 1353-1368 ◽  
Author(s):  
Nathalie Pytlik ◽  
Daniel Butscher ◽  
Susanne Machill ◽  
Eike Brunner
Keyword(s):  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Attenuated Total Reflection ◽  
Emission Spectrometry ◽  
Green Catalyst ◽  
X Ray ◽  
Inductively Coupled ◽  
Silica Nanocomposites ◽  
Green Approach ◽  
Plasma Optical Emission Spectrometry

Abstract Biosynthesis by diatoms provides a green approach for nanoparticle (NP) production. However, reproducible and homogeneous shapes are essential for their application. To improve these characteristics during biosynthesis, the underlying synthesis mechanisms as well as involved substances need to be understood. The first essential step for suitable analyses is the purification of Au-silica-nanocomposites from organic biomass. Succesfully cleaned nanocomposites could, for example, be useful as catalysts. In combination with the biosynthesized NPs, this material presents a “green” catalyst and could contribute to the currently thriving green nanochemistry. In this work, we compare different purification agents with respect to their ability to purify cells of the diatom Stephanopyxis turris without separating the biosynthesized Au-silica-nanocomposites from the diatom cell walls. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are used to localize and identify Au-silica-nanocomposites around the cells. The amount of remaining organic compounds on the purified cell is detected by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Furthermore, inductively coupled plasma optical emission spectrometry (ICP-OES) is used to track the “gold path” during cell growth and the different purifications steps.

scholarly journals Revealing the reactivity of the Iridium trioxide intermediate for the oxygen evolution reaction in acidic media

2019 ◽  
Author(s):  
Paul Pearce ◽  
Chunzhen Yang ◽  
Antonella Iadecola ◽  
Juan Rodriguez-Carvajal ◽  
Gwenaëlle Rousse ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Photoelectron Spectroscopy ◽  
Oxygen Evolution Reaction ◽  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Charge Compensation ◽  
Acidic Media ◽  
X Ray ◽  
Inductively Coupled ◽  
Reaction With Water

We report a strategy to isolate IrO<sub>3</sub> as an intermediate for the oxygen evolution reaction (OER). Its reactivity is studied using X-ray absorption spectroscopy, X-ray and neutron diffraction and X-ray photoelectron spectroscopy. Its stability is assessed by using on-line mass spectroscopy and inductively coupled plasma optical emission spectroscopy and presented herein. Upon reaction with water in acidic conditions, we could observe the formation of a new protonated iridate phase of composition H<sub>2</sub>IrO<sub>3</sub>. Coupling OER measurements and dissolution rate determination, we could show that its activity and stability are governed by a yet ill-described charge compensation mechanism enlisting reversible bulk proton insertion inside the catalyst structure. This singular property enables an enhanced activity and stability towards dissolution compared to the stellar IrO<sub>x</sub>/SrIrO<sub>3</sub> catalyst. Such a finding opens the route towards the design of new OER catalysts enlisting proton insertion that could be competitive for water splitting in acidic media.<br>

scholarly journals A Facile Synthesis of MoS2/g-C3N4 Composite as an Anode Material with Improved Lithium Storage Capacity

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1730 ◽  
Author(s):  
Ha Tran Huu ◽  
Xuan Dieu Nguyen Thi ◽  
Kim Nguyen Van ◽  
Sung Jin Kim ◽  
Vien Vo
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Performance ◽  
Photoelectron Spectroscopy ◽  
Gas Flow ◽  
Electrode Materials ◽  
High Capacity ◽  
Sodium Molybdate ◽  
Lithium Ion ◽  
Lithium Storage ◽  
X Ray

The demand for well-designed nanostructured composites with enhanced electrochemical performance for lithium-ion batteries electrode materials has been emerging. In order to improve the electrochemical performance of MoS2-based anode materials, MoS2 nanosheets integrated with g-C3N4 (MoS2/g-C3N4 composite) was synthesized by a facile heating treatment from the precursors of thiourea and sodium molybdate at 550 °C under N2 gas flow. The structure and composition of MoS2/g-C3N4 were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and elemental analysis. The lithium storage capability of the MoS2/g-C3N4 composite was evaluated, indicating high capacity and stable cycling performance at 1 C (A·g−1) with a reversible capacity of 1204 mA·h·g−1 for 200 cycles. This result is believed the role of g-C3N4 as a supporting material to accommodate the volume change and improve charge transport for nanostructured MoS2. Additionally, the contribution of the pseudocapacitive effect was also calculated to further clarify the enhancement in Li-ion storage performance of the composite.

scholarly journals Rhodium Nanoparticles Stabilized by PEG-Tagged Imidazolium Salts as Recyclable Catalysts for the Hydrosilylation of Internal Alkynes and the Reduction of Nitroarenes

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1195
Author(s):  
Guillem Fernández ◽  
Roser Pleixats
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Optical Emission ◽  
Water Soluble ◽  
X Ray ◽  
Rhodium Nanoparticles ◽  
Inductively Coupled ◽  
Transmission Electron ◽  
Internal Alkynes ◽  
Recyclable Catalysts

PEGylated imidazolium (bromide and tetrafluoroborate) and tris-imidazolium (bromide) salts containing triazole linkers have been used as stabilizers for the preparation of water-soluble rhodium(0) nanoparticles by reduction of rhodium trichloride with sodium borohydride in water at room temperature. The nanomaterials have been characterized (Transmission Electron Microscopy, Electron Diffraction, X-ray Photoelectron Spectroscopy, Inductively Coupled Plasma-Optical Emission Spectroscopy). They proved to be efficient and recyclable catalysts for the stereoselective hydrosilylation of internal alkynes, in the presence or absence of solvent, and in the reduction of nitroarenes to anilines with ammonia-borane as hydrogen donor in aqueous medium (1:4 tetrahydrofuran/water).

scholarly journals Hydrothermal Synthesis of TiO2 Aggregates and Their Application as Negative Electrodes for Lithium-Ion Batteries: The Conflicting Effects of Specific Surface and Pore Size

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 916
Author(s):  
Saida Mehraz ◽  
Wenpo Luo ◽  
Jolanta Swiatowska ◽  
Boudjema Bezzazi ◽  
Abdelhafed Taleb
Keyword(s):  
Hydrothermal Synthesis ◽  
Specific Surface ◽  
Pore Size ◽  
Lithium Ion Batteries ◽  
Photoelectron Spectroscopy ◽  
Electrode Materials ◽  
Lithium Ion ◽  
Synthesis Temperature ◽  
X Ray ◽  
Surface Areas

TiO2 aggregates of controlled size have been successfully prepared by hydrothermal synthesis using TiO2 nanoparticles of different sizes as a building unit. In this work, different techniques were used to characterize the as-prepared TiO2 aggregates, e.g., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer, Emmett and Teller technique (BET), field emission gun scanning electron microscopy (FEGSEM), electrochemical measurements etc. The size of prepared TiO2 aggregates varied from 10–100 nm, and their pore size from around 5–12 nm; this size has been shown to depend on synthesis temperature. The mechanism of the aggregate formations was discussed in terms of efficiency of collision and coalescence processes. These newly synthetized TiO2 aggregates have been investigated as potential negative insertion electrode materials for lithium-ion batteries. The influence of specific surface areas and pore sizes on the improved capacity was discussed—and conflicting effects pointed out.

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