scholarly journals Structurally Dependent Electrochemical Properties of Ultrafine Superparamagnetic ‘Core/Shell’ γ-Fe2O3/Defective α-Fe2O3 Composites in Hybrid Supercapacitors

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6977
Author(s):  
Oleg Bazaluk ◽  
Andrii Hrubiak ◽  
Volodymyr Moklyak ◽  
Maria Moklyak ◽  
Lina Kieush ◽  
...  
Keyword(s):  
Discharge Capacity ◽  
Sol Gel ◽  
Morphological Characteristics ◽  
Electrochemical Activity ◽  
Core Shell ◽  
Subsequent Formation ◽  
Hybrid Supercapacitors ◽  
Specific Discharge ◽  
Coulomb Efficiency ◽  
Synthesized Materials

The paper presents a method for obtaining electrochemically active ultrafine composites of iron oxides, superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O3, which involved modifying sol-gel citrate synthesis, hydrothermal treatment of the formed sol, and subsequent annealing of materials in the air. The synthesized materials’ phase composition, magnetic microstructure, and structural, morphological characteristics have been determined via X-ray analysis, Mossbauer spectroscopy, scanning electron microscopy (SEM), and adsorption porometry. The mechanisms of phase stability were analyzed, and the model was suggested as FeOOH ® γ-Fe2O3 ® α-Fe2O3. It was found that the presence of chelating agents in hydrothermal synthesis encapsulated the nucleus of the new phase in the reactor and interfered with the direct processes of recrystallization of the structure with the subsequent formation of the α- Fe2O3 crystalline phase. Additionally, the conductive properties of the synthesized materials were determined by impedance spectroscopy. The electrochemical activity of the synthesized materials was evaluated by the method of cyclic voltammetry using a three-electrode cell in a 3.5 M aqueous solution of KOH. For the ultrafine superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O composite with defective hematite structure and the presence of ultra-dispersed maghemite with particles in the superparamagnetic state was fixed increased electrochemical activity, and specific discharge capacity of the material is 177 F/g with a Coulomb efficiency of 85%. The prototypes of hybrid supercapacitor with work electrodes based on ultrafine composites superparamagnetic ‘core/shell’ γ-Fe2O3/defective α-Fe2O3 have a specific discharge capacity of 124 F/g with a Coulomb efficiency of 93% for current 10 mA.

scholarly journals In-Situ Arc Discharge-Derived FeSn2/Onion-Like Carbon Nanocapsules as Improved Stannide-Based Electrocatalytic Anode Materials for Lithium-Ion Batteries

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 950 ◽  
Author(s):  
Dandan Han ◽  
Amrita Chatterjee ◽  
Long Hin Man ◽  
Siu Wing Or
Keyword(s):  
Crystal Growth ◽  
Discharge Capacity ◽  
Arc Discharge ◽  
Lithium Ion ◽  
Core Shell ◽  
Discharge Process ◽  
Capacity Retention ◽  
Specific Discharge ◽  
Charge Discharge

Core/shell-structured FeSn2/onion-like carbon (FeSn2/OLC) nanocapsules of confined size range of sub-50 nm are synthesized via an in-situ arc-discharge process, and are evaluated in comparison with FeSn2 nanoparticles as an improved stannide-based electrocatalytic anode material for Li-ion batteries (LIBs). The in-situ arc-discharge process allows a facile one-pot procedure for forming crystalline FeSn2 stannide alloy nanoparticle cores coated by defective OLC thin shells in addition to a confined crystal growth of the FeSn2 nanoparticle cores. The LIB cells assembled using the FeSn2/OLC nanocapsules as the electrocatalytic anodes exhibit superior full specific discharge capacity of 519 mAh·g−1 and specific discharge capacity retention of ~62.1% after 100 charge-discharge cycles at 50 mA·g−1 specific current. The electrochemical stability of FeSn2/OLC nanocapsules is demonstrated from the good cycle stability of the LIBs with a high specific discharge capacity retention of 67.5% on a drastic change in specific current from 4000 to 50 mA·g−1. A formation mechanism is proposed to describe the confined crystal growth of the FeSn2 nanoparticle cores and the formation of the FeSn2/OLC core/shell structure. The observed electrochemical performance enhancement is ascribed to the synergetic effects of the enabling of a reversible lithiation process during charge-discharge of the LIB cells by the FeSn2 nanoparticle cores as well as the protection of the FeSn2 nanoparticle cores from volume change-induced pulverization and solid electrolyte interphase-induced passivation by the OLC shells.

High-Performance Multi-Layers Tubular Nanostructure Anode Materials for Lithium-Ion Batteries

NANO ◽  
2020 ◽  
Vol 15 (04) ◽  
pp. 2050053 ◽  
Author(s):  
Yanbo Li ◽  
Ke Li ◽  
Jinjie Liu ◽  
Xi Zhang ◽  
Jintao Dai ◽  
...  
Keyword(s):  
Anode Material ◽  
Discharge Capacity ◽  
Anode Materials ◽  
High Performance ◽  
Sol Gel ◽  
Reduction Process ◽  
Lithium Ion ◽  
Volume Effect ◽  
Active Materials ◽  
Specific Discharge

In order to reduce the negative volume effect of Silicon (Si) and Silica (SiO[Formula: see text] as anode materials, CNTs@SiO2/Si@C is prepared by sol–gel method and magnesiothermic reduction process. SEM and TEM results show that the surface of Carbon nanotubes (CNTs) is uniformly coated with active materials including SiO2 and Si. Active materials (SiO2/Si) closely contact with the conductive network constructed by CNTs, which greatly improves the conductivity of the composite anode material. Moreover, the large specific surface area of the tubular structure provides more Li[Formula: see text] diffusion channel. The cushion space of the hollow tube structure effectively alleviates the volume effect of SiO2/Si and enables the anode material excellent electrochemical performance in the cycling test. The initial discharge capacity of CNTs@SiO2/Si@C is 1064[Formula: see text]mAh/g at current density of 200 mA/g. The specific discharge capacity of CNTs@SiO2/Si@C is higher than 960 mAh/g after 100 cycles, and the coulomb efficiency maintains over 98% in the range from 30th to 100th cycle.

scholarly journals High Capacity Prismatic Type Layered Electrode with Anionic Redox Activity as an Efficient Cathode Material and PVdF/SiO2 Composite Membrane for a Sodium Ion Battery

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 662 ◽  
Author(s):  
Arjunan Ponnaiah ◽  
Subadevi Rengapillai ◽  
Diwakar Karuppiah ◽  
Sivakumar Marimuthu ◽  
Wei-Ren Liu ◽  
...  
Keyword(s):  
Cathode Material ◽  
Discharge Capacity ◽  
Sol Gel ◽  
High Capacity ◽  
Charge Compensation ◽  
Sodium Ion ◽  
Redox Activity ◽  
Sodium Ion Battery ◽  
Voltage Range ◽  
Specific Discharge

A prismatic type layered Na2/3Ni1/3Mn2/3O2 cathode material for a sodium ion battery is prepared via two different methods viz., the solid state and sol–gel method with dissimilar surface morphology and a single phase crystal structure. It shows tremendous electrochemical chattels when studied as a cathode for a sodium-ion battery of an initial specific discharge capacity of 244 mAh g−1 with decent columbic efficiency of 98% up to 250 cycles, between the voltage range from 1.8 to 4.5 V (Na+/Na) at 0.1 C under room temperature. It is much higher than its theoretical value of 173 mAh g−1 and also than in the earlier reports (228 m Ah g−1). The full cell containing this material exhibits 800 mAh g−1 at 0.1 C and withstands until 1000 cycles with the discharge capacity of 164 mAh g−1. The surpassing capacity was expected by the anionic (oxygen) redox process, which elucidates the higher capacity based on the charge compensation phenomenon.

Core-shell nanostructured Zn-Co-O@CoS arrays for high-performance hybrid supercapacitors

2021 ◽  
Author(s):  
Yi He ◽  
Lei Xie ◽  
Shixiang Ding ◽  
Yujia Long ◽  
Xinyi Zhou ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Energy Storage ◽  
Active Sites ◽  
High Performance ◽  
Electronic Conductivity ◽  
Wide Distribution ◽  
Energy Storage Materials ◽  
Core Shell ◽  
Storage Materials ◽  
Hybrid Supercapacitors

Although the zinc oxide (ZnO) with wide distribution is one of the most attractive energy storage materials, the low electronic conductivity and insufficient active sites of bulk ZnO increase the...

Performance of rectangular labyrinth weir- an experimental and numerical study

2022 ◽  
Author(s):  
Mosbah Ben Said ◽  
Ahmed Ouamane
Keyword(s):  
Discharge Capacity ◽  
Numerical Study ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Experimental Models ◽  
Absolute Relative Error ◽  
Labyrinth Weir ◽  
Specific Discharge ◽  
Labyrinth Weirs ◽  
Good Agreement

Abstract Labyrinth weirs are commonly used to increase the capacity of existing spillways and provide more efficient spillways for new dams due to their high specific discharge capacity compared to the linear weir. In the present study, experimental and numerical investigation was conducted to improve the rectangular labyrinth weir performance. In this context, four configurations were tested to evaluate the influence of the entrance shape and alveoli width on its discharge capacity. The experimental models, three models of rectangular labyrinth weir with rounded entrance and one with flat entrance, were tested in rectangular channel conditions for inlet width to outlet width ratios (a/b) equal to 0.67, 1 and 1.5. The results indicate that the rounded entrance increases the weir efficiency by up to 5%. A ratio a/b equal to 1.5 leads to an 8 and 18% increase in the discharge capacity compared to a/b ratio equal to 1 and 0.67, respectively. In addition, a numerical simulation was conducted using the opensource CFD OpenFOAM to analyze and provide more information about the flow behavior over the tested models. A comparison between the experimental and numerical discharge coefficient was performed and good agreement was found (Mean Absolute Relative Error of 4–6%).

Cytotoxicity of Thermoresponsive Core/Shell NixCo1-xFe2O4/PEG Nanoparticles Synthesized by Sol-gel Method

2021 ◽  
Author(s):  
Amirhossein Esmaeilkhanian ◽  
Fariborz Sharifianjazi ◽  
Nader Parvin ◽  
Mohammad Amin Koti
Keyword(s):  
Sol Gel ◽  
Core Shell ◽  
Gel Method ◽  
Sol Gel Method

Tungsten carbide/porous carbon core–shell nanocomposites as a catalyst support for methanol oxidation

RSC Advances ◽  
2016 ◽  
Vol 6 (17) ◽  
pp. 13873-13880 ◽  
Author(s):  
Xiaoling Lang ◽  
Meiqin Shi ◽  
Yekun Jiang ◽  
Huan Chen ◽  
Chunan Ma
Keyword(s):  
Synergistic Effect ◽  
Tungsten Carbide ◽  
Methanol Oxidation ◽  
Porous Carbon ◽  
Catalyst Support ◽  
Electrochemical Activity ◽  
Core Shell ◽  
Carbon Core

The Pt–WC@C demonstrates higher electrochemical activity, which could be attributed to the better dispersed Pt on WC which leads to the improved synergistic effect between WC and Pt.

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