Role of Additives in Electrochemical Deposition of Ternary Metal Oxide Microspheres for Supercapacitor Applications

Experimental and theoretical investigation on the charge storage performance of NiSb2O6 and its reduced graphene oxide composite - a comparative analysis

We report the electrochemical charge storage performance of NiSb2O6, obtained through a solid-state reaction method, and a detailed comparison with its reduced graphene oxide composite. Intriguingly, the composite, NiSb2O6-reduced graphene oxide, yielded a large capacitance of 952.38 F g-1, at a mass-normalized-current of 1 A g-1, which is at least 4-fold higher than that of the bare NiSb2O6. We have also tested the performance of the composite in a two-electrode symmetric device. The NiSb2O6-reduced graphene oxide symmetric device showed an excellent capacity retention of ∼94%, even after 10 000 cycles. We conducted comprehensive density functional theory (DFT) simulations to determine the structure and electronic characteristics of NiSb2O6, and the composite material of NiSb2O6-reduced graphene oxide. The incorporation of reduced graphene oxide results in an augmentation of electronic states near the Fermi level, hence showing an improvement in the conductivity of the hybrid system. The composite structure exhibits a lower diffusion energy barrier for electrolyte ions and a greater quantum capacitance than pristine NiSb2O6. These characteristics confirm our experimental findings and justify the observed improvement in charge storage performance for the composite structure. Based on the results obtained, it can be concluded that the combination of rGO and NiSb2O6 displays excellent performance and has the potential to serve as a highly efficient material for electrochemical capacitors.

Rational Construction of Pt Incorporated Co3O4 as High-Performance Electrocatalyst for Hydrogen Evolution Reaction

Electrocatalysts in alkaline electrocatalytic water splitting are required to efficiently produce hydrogen while posing a challenge to show excellent performances. Herein, we have successfully synthesized platinum nanoparticles incorporated in a Co3O4 nanostructure (denoted as Pt-Co3O4) that show superior HER activity and stability in alkaline solutions (the overpotentials of 37 mV to reach 10 mA cm-2). The outstanding electrocatalytic activity originates from synergistic effects between Pt and Co3O4 and increased electron conduction. Theoretical calculations show a significant decrease in the ΔGH* of Co active sites and a remarkable increase in electron transport. Our work puts forward a special and simple synthesized way of adjusting the H* adsorption energy of an inert site for application in HER.

Electrodeposited Copper Tin Sulfide/Reduced Graphene Oxide Nanospikes for a High-Performance Supercapacitor Electrode

Copper tin sulfide, Cu4SnS4 (CTS), a ternary transition-metal chalcogenide with unique properties, including superior electrical conductivity, distinct crystal structure, and high theoretical capacity, is a potential candidate for supercapacitor (SC) electrode materials. However, there are few studies reporting the application of Cu4SnS4 or its composites as electrode materials for SCs. The reported performance of the Cu4SnS4 electrode is insufficient regarding cycle stability, rate capability, and specific capacity; probably resulting from poor electrical conductivity, restacking, and agglomeration of the active material during continued charge-discharge cycles. Such limitations can be overcome by incorporating graphene as a support material and employing a binder-free, facile, electrodeposition technique. This work reports the fabrication of a copper tin sulfide-reduced graphene oxide/nickel foam composite electrode (CTS-rGO/NF) through stepwise, facile electrodeposition of rGO and CTS on a NF substrate. Electrochemical evaluations confirmed the enhanced supercapacitive performance of the CTS-rGO/NF electrode compared to that of CTS/NF. A remarkably improved specific capacitance of 820.83 F g-1 was achieved for the CTS-rGO/NF composite electrode at a current density of 5 mA cm-2, which is higher than that of CTS/NF (516.67 F g-1). The CTS-rGO/NF composite electrode also exhibited a high-rate capability of 73.1% for galvanostatic charge-discharge (GCD) current densities, ranging from 5 to 12 mA cm-2, and improved cycling stability with over a 92% capacitance retention after 1000 continuous GCD cycles; demonstrating its excellent performance as an electrode material for energy storage applications, encompassing SCs. The enhanced performance of the CTS-rGO/NF electrode could be attributed to the synergetic effect of the enhanced conductivity and surface area introduced by the inclusion of rGO in the composite.

Prussian blue analogue-derived hollow metal oxide heterostructure for high-performance supercapacitors

Supercapacitors (SCs) have been the subject of considerable interest because of their distinct advantages. The performance of SCs is directly affected by the electrode materials. Metal oxides derived from Prussian blue analogues (PBAs) are often used as electrode materials for SCs. Herein, we developed a multi-step strategy to fabricate ternary hollow metal oxide (CuO/NiO/Co3O4) heterostructures. The core-shell structured PBA (NiHCC@CuHCC) with Ni-based PBA (NiHCC) as the core and Cu-based PBA (CuHCC) as the shell was prepared by a crystal seed method. The ternary metal oxide (CuO/NiO/Co3O4) with a hollow structure was obtained by calcinating NiHCC@CuHCC. The prepared CuO/NiO/Co3O4 demonstrates an excellent specific capacitance of 262.5 F g-1 at 1 A g-1, which is 27.4% and 16.2% higher than those of CuO/Co3O4 and NiO/Co3O4, respectively. In addition, the material showed outstanding cycling stability with a capacitance retention of 107.9% after 3000 cycles. The two-electrode system constructed with CuO/NiO/Co3O4 and nitrogen-doped graphene hydrogel (NDGH) demonstrates a stable and high energy density of 27.1 W h kg-1 at a power density of 1037.5 W kg-1. The capacitance retention rate was 100.7% after 4000 cycles. The reason for the excellent electrochemical properties could be the synergistic effect of the introduced heterojunction of CuO/NiO, the hollow structure, and various metal oxides. This strategy can greatly inspire the construction of SC electrodes.

Hollow Porous CoO@Reduced Graphene Oxide Self-Supporting Flexible Membrane for High Performance Lithium-Ion Storage

We report an environment-friendly preparation method of rGO-based flexible self-supporting membrane electrodes, combining Co-MOF with graphene oxide and quickly preparing a hollow CoO@rGO flexible self-supporting membrane composite with a porous structure. This unique hollow porous structure can shorten the ion transport path and provide more active sites for lithium ions. The high conductivity of reduced graphene oxide further facilitates the rapid charge transfer and provides sufficient buffer space for the hollow Co-MOF nanocubes during the charging process. We evaluated its electrochemical performance in a coin cell, which showed good rate capability and cycling stability. The CoO@rGO flexible electrode maintains a high specific capacity of 1103 mAh g^-1 after 600 cycles at 1.0 A g^-1. The high capacity of prepared material is attributed to the synergistic effect of the hollow porous structure and the 3D reduced graphene oxide network. This would be considered a promising new strategy for synthesizing hollow porous-structured rGO-based self-supported flexible electrodes.

Microplotter Printing of a Miniature Flexible Supercapacitor Electrode Based on Hierarchically Organized NiCo2O4 Nanostructures

The hydrothermal synthesis of a nanosized NiCo₂O₄ oxide with several levels of hierarchical self-organization was studied. Using X-ray diffraction analysis (XRD) and Fourier-transform infrared (FTIR) spectroscopy, it was determined that under the selected synthesis conditions, a nickel-cobalt carbonate hydroxide hydrate of the composition M(CO₃)_0.5(OH)·0.11H₂O (where M-Ni²⁺ and Co²⁺) is formed as a semi-product. The conditions of semi-product transformation into the target oxide were determined by simultaneous thermal analysis. It was found by means of scanning electron microscopy (SEM) that the main powder fraction consists of hierarchically organized microspheres of 3-10 μm in diameter, and individual nanorods are observed as the second fraction of the powder. Nanorod microstructure was further studied by transmission electron microscopy (TEM). A hierarchically organized NiCo₂O₄ film was printed on the surface of a flexible carbon paper (CP) using an optimized microplotter printing technique and functional inks based on the obtained oxide powder. It was shown by XRD, TEM, and atomic force microscopy (AFM) that the crystalline structure and microstructural features of the oxide particles are preserved when deposited on the surface of the flexible substrate. It was found that the obtained electrode sample is characterized by a specific capacitance value of 420 F/g at a current density of 1 A/g, and the capacitance loss during 2000 charge-discharge cycles at 10 A/g is 10%, which indicates a high material stability. It was established that the proposed synthesis and printing technology enables the efficient automated formation of corresponding miniature electrode nanostructures as promising components for flexible planar supercapacitors.

Effect of High-Energy Ball Milling, Capping Agents and Alkalizer on Capacitance of Nanostructured FeOOH Anodes

This investigation is motivated by interest in nanostructured FeOOH anodes for aqueous asymmetric supercapacitors operating in Na₂SO₄ electrolyte. The research goal is the fabrication of anodes with high active mass loading of 40 mg cm^-2, high capacitance and low resistance. The influence of high-energy ball milling (HEBM), capping agents and alkalizer on the nanostructure and capacitive properties is investigated. HEBM promotes the crystallization of FeOOH, which results in capacitance reduction. Capping agents from the catechol family, such as tetrahydroxy-1,4-benzoquinone (THB) and gallocyanine (GC), facilitate the fabrication of FeOOH nanoparticles, eliminate the formation of micron size particles and allow the fabrication of anodes with enhanced capacitance. The analysis of testing results provided insight into the influence of the chemical structure of the capping agents on nanoparticle synthesis and dispersion. The feasibility of a conceptually new strategy for the synthesis of FeOOH nanoparticles is demonstrated, which is based on the use of polyethylenimine as an organic alkalizer-dispersant. The capacitances of materials prepared using different nanotechnology strategies are compared. The highest capacitance of 6.54 F cm^-2 is obtained using GC as a capping agent. The obtained electrodes are promising for applications as anodes for asymmetric supercapacitors.

Microwave-Assisted Hierarchically Grown Flake-like NiCo Layered Double Hydroxide Nanosheets on Transitioned Polystyrene towards Triboelectricity-Driven Self-Charging Hybrid Supercapacitors

Recently, there is a need to explore the utilization of various heterostructures using the designed nanocomposites and tuning the surfaces of electrodes for improving the electrochemical performance of supercapacitors (SC). In this work, a novel approach is successfully employed through a facile two-step synthetic route with the assistance of a microwave for only 1 min. Depending on the glass transition of a polystyrene (PS) substrate and electrochemical deposition (ECD) of electroactive Ni-Co layered double hydroxides (LDHs), a hierarchically designed flake-like morphology can be readily prepared to enhance the surface-active sites, which allows a rhombohedral Ni-Co LDHs electrode to obtain superior electrochemical properties. Further, the interactions between electrode and electrolyte during the diffusion of ions are highly simplified using multiple enhanced electroactive sites and shorter pathways for electron transfer. The unique surface architecture of the PS substrate and the synergistic effect of the bimetallic components in Ni-Co LDHs enable this substrate to obtain desired electrochemical activity in charge storage systems. The optimized MWC Co_0.5Ni_0.5 electrode exhibited an areal capacity of 100 µAh/cm² at a current density of 1 mA/cm² and a remarkable capacity retention of 91.2% over 5000 continuous charging and discharging cycles due to its remarkable synergistic effect of abundant faradaic redox reaction kinetics. The HSC device is assembled with the combination of optimized MWC Co_0.5Ni_0.5 and activated carbon as a positive and negative electrode, respectively. Further, the electrochemical test results demonstrated that MWC Co_0.5Ni_0.5 //AC HSC device showed a high areal capacitance of 531.25 mF/cm² at a current density of 5 mA/cm². In addition, the fabricated an aqueous HSC device showed a power density of 16 mW/cm² at an energy density of 0.058 mWh/cm², along with the remarkable capacity retention of 82.8% even after 10,000 continuous charging and discharging cycles. Moreover, the assembled hybrid supercapacitor (HSC) device is integrated with a triboelectric nanogenerator (TENG) for the development of energy conversion and storage systems. Not only an extensive survey of materials but also an innovative solution for recent progress can confirm the wide range of potential SC applications. Remarkably, this study is a new way of constructing self-powered energy storage systems in the field of sustainable wearable electronics and future smart sensing systems.

In Situ Grown Mesoporous Structure of Fe-Dopant@NiCoOX@NF Nanoneedles as an Efficient Supercapacitor Electrode Material

In this study, we designed mixed metal oxides with doping compound nano-constructions as efficient electrode materials for supercapacitors (SCs). We successfully prepared the Fe-dopant with NiCoOx grown on nickel foam (Fe-dopant@NiCoOx@NF) through a simple hydrothermal route with annealing procedures. This method provides an easy route for the preparation of high activity SCs for energy storage. Obtained results revealed that the Fe dopant has successfully assisted NiCoOx lattices. The electrochemical properties were investigated in a three-electrode configuration. As a composite electrode for SC characteristics, the Fe-dopant@NiCoOx@NF exhibits notable electrochemical performances with very high specific capacitances of 1965 F g−1 at the current density of 0.5 A g−1, and even higher at 1296 F g−1 and 30 A g−1, respectively, which indicate eminent and greater potential for SCs. Moreover, the Fe-dopant@NiCoOx@NF nanoneedle composite obtains outstanding cycling performances of 95.9% retention over 4500 long cycles. The improved SC activities of Fe-dopant@NiCoOx@NF nanoneedles might be ascribed to the synergistic reactions of the ternary mixed metals, Fe-dopant, and the ordered nanosheets grown on NF. Thus, the Fe-dopant@NiCoOx@NF nanoneedle composite with unique properties could lead to promising SC performance.

Features of Galvanostatic Electrodeposition of NiFe Films with Composition Gradient: Influence of Substrate Characteristics

NiFe films with a composition gradient are of particular interest from the point of view of fundamental science and practical applications. Such gradient magnetic structures may exhibit unique functional properties useful for sensory applications and beyond. The issue surrounds the anomaly concerning the compositional gradient formed near the substrate in electrolytically deposited binary and ternary iron-containing alloys, which has not previously been clearly explained. In this work, light is shed on this issue, and a clear relationship is found between the structure and surface properties of the substrate, the initially formed NiFe layers and the film composition gradient.

Nanostructuring Effect of Nano-CeO2 Particles Reinforcing Cobalt Matrix during Electrocodeposition Process

The electrodeposition method was used to obtain nanostructured layers of Co/nano-CeO₂ on 304L stainless steel, from a cobalt electrolyte in which different concentrations of CeO₂ nanoparticles (0, 10, 20, and 30 g/L) were dispersed. The electrodeposition was performed at room temperature using three current densities (23, 48, and 72 mA cm^-2), and the time was kept constant at 90 min. The influence of current densities and nanoparticle concentrations on the characteristics of the obtained nanostructured layers is also discussed. An X-ray diffractometer (XRD) was used to investigate the phase structure and cobalt crystallite size of the nanostructured layers, and a contact angle (sessile drop method) was used to assess the wettability of the electrodeposited layers. The roughness of the surfaces was also studied. The results show that the nanostructured layers became more hydrophilic with increasing nanoparticle concentration and increasing current density. In the case of pure cobalt deposits, an increase in the current density led to an increase in the size of the cobalt crystallites in the electrodeposited layer, while for the Co/nano-CeO₂ nanostructured layers, the size of the crystallites decreased with increasing current density. This confirms the nanostructuring effect of nano-CeO₂ electrocodeposited with cobalt.

Electrodeposition of CoxNiVyOz Ternary Nanopetals on Bare and rGO-Coated Nickel Foam for High-Performance Supercapacitor Application

We report a simple strategy to grow a novel cobalt nickel vanadium oxide (CoxNiVyOz) nanocomposite on bare and reduced-graphene-oxide (rGO)-coated nickel foam (Ni foam) substrates. In this way, the synthesized graphene oxide is coated on Ni foam, and reduced electrochemically with a negative voltage to prepare a more conductive rGO-coated Ni foam substrate. The fabricated electrodes were characterized with a field-emission scanning electron microscope (FESEM), energy-dispersive X-ray spectra (EDX), X-ray photoelectron spectra (XPS), and Fourier-transform infrared (FTIR) spectra. The electrochemical performance of these CoxNiVyOz-based electrode materials deposited on rGO-coated Ni foam substrate exhibited superior specific capacitance 701.08 F/g, which is more than twice that of a sample coated on bare Ni foam (300.31 F/g) under the same experimental conditions at current density 2 A/g. Our work highlights the effect of covering the Ni foam surface with a rGO film to expedite the specific capacity of the supercapacitors. Despite the slightly decreased stability of a CoxNiVyOz-based electrode coated on a Ni foam@rGO substrate, the facile synthesis, large specific capacitance, and preservation of 92% of the initial capacitance, even after running 5500 cyclic voltammetric (CV) scans, indicate that the CoxNiVyOz-based electrode is a promising candidate for high-performance energy-storage devices.

Simultaneous Electrodeposition of Ternary Metal Oxide Nanocomposites for High-Efficiency Supercapacitor Applications

Complex oxides and hydroxides of Ni, Co, and Mn from a precursor mixture were electrochemically deposited on both a cathode and an anode. On the Ni foam cathode, the complex metal hydroxides precipitated as nanolayers at -0.9 V. Simultaneously, the metal ions were oxidized and deposited as blocks on the Ni foam anode. While the concentrations of Ni(NO₃)₂ and Mn(NO₃)₂ were constant (80 mM for Ni²⁺ and 40 mM for Mn²⁺, respectively), the concentration of Co(NO₃)₂ was varied from 20 to 120 mM, which affected the morphology and electrochemical properties of the electrode: a Co:Ni:Mn molar ratio resulted in the highest specific capacitance (at a scan rate of 5 mV s^-1, 1800 F g^-1 for the cathode material and 720 F g^-1 for the anode material). This cathode material was assembled into symmetric supercapacitors, which demonstrated an excellent energy density of 39 Wh kg^-1 at a power density of 1300 W kg^-1 and a high capacitance retention of 90% after 3000 charge/discharge cycles. This high electrochemical performance was attributed to the optimized ratio of metal oxides, and this simple preparation strategy can be applied to other nanocomposites of complex metal oxides/hydroxides with desired characteristics for various applications.

Ready-to-use binder-free Co(OH)2 plates@porous rGO layers/Ni foam electrode for high-performance supercapacitors

In this work, an outstanding nano-structured composite electrode is fabricated through the co-deposition of Co(OH)2 nanoplates and porous reduced GO (p-rGO) nanosheets onto Ni foam (NF). Through field emission scanning electron microscopy and transmission electron microscopy observations, it was confirmed that porous reduced graphene oxide sheets are completely wrapped by uniform hexagonal Co(OH)2 plates. Due to the unique architecture of both components of the prepared composite, a high surface area of 234.7 m2 g-1 and mean pore size of 3.65 nm were observed for the Co(OH)2@p-rGO composite. The constructed Co(OH)2@p-rGO/NF composite electrode shows higher energy storage capability compared to that of Co(OH)2/NF and p-rGO/NF electrodes. The Co(OH)2/NF electrode shows specific capacitances of 902 and 311 F g-1 at 5 and 30 A g-1, while the Co(OH)2@p-rGO/NF electrode delivers 1688 and 1355 F g-1 under the same current loads, respectively. Furthermore, when the current load was increased from 1 to 30 A g-1, 74.5% capacitance retention was observed for the Co(OH)2@p-rGO/NF electrode, indicating its outstanding high-power capability, while the Co(OH)2/NF electrode retained only 38.5% of its initial capacitance. The fabricated Co(OH)2@p-rGO/NF//rGO/NF ASC device shows an areal capacitance of 3.29 F cm-2, cycling retention of 91.2% after 4500 cycles at 5 A g-1 and energy density of 68.7 W h kg-1 at a power density of 895 W kg-1. The results of electrochemical tests prove that Co(OH)2@p-rGO/NF exhibits good performance as a positive electrode for use in an asymmetric supercapacitor device. The prepared porous composite electrode is thus a promising candidate for use in supercapacitor applications.

Recent Advancements in Electrochemical Deposition of Metal-Based Electrode Materials for Electrochemical Supercapacitors

The demand for energy storage devices with high energy and power densities has increased tremendously in this rapidly growing world. Conventional capacitors, fuel cells, and lithium-ion batteries have been used as energy storage devices for the long term. However, supercapacitors are one of the most promising energy storage devices because of their high specific capacitance, high power density, and longer cycle life. Recent research has focused on synthesizing transition-metal oxides/hydroxides, carbon materials, and conducting polymers as supercapacitor electrode materials. The performance of supercapacitors can be improved by altering electrolytes, electrode materials, current collectors, experimental temperatures, and film thickness. Thousands of papers on supercapacitors have already been published, reflecting the significance and elucidating how much demanding such energy storage devices for this fast-growing generation. This review aims to illustrate the electrode materials loaded on various conductive substrates by electrochemical deposition employed for supercapacitors to provide broad knowledge on synthetic pathways, which will pave the way for future research. We also discussed the basic parameters involved in supercapacitor studies and the advantages of the electrochemical deposition techniques through literature analysis. Finally, future trends and directions on exploring metals/metal composites toward designing and constructing viable, high-class, and even newly featured flexible energy storage materials, electrodes, and systems are presented.

Highly Efficient Capacitive Deionization Enabled by NiCo4MnO8.5 Electrodes

The shortage of fresh water resources is one of the major challenges facing this planet. Capacitive deionization (CDI) techniques that are deemed to be highly efficient and require low capital cost have attracted widespread attention in the last few decades. In this work, the cubic ternary metal oxides NiCo4MnO8.5 (Ni-Co-Mn-O) are synthesized by facile hydrothermal method for enhanced symmetrical CDI. Electrochemical measurements illustrate that the Ni-Co-Mn-O possesses low internal resistance and ion diffusion impedance. As a result, the salt removal capacity of the Ni-Co-Mn-O electrode increases from 26.84 to 65.61 mg g-1 by varying the voltage from 0.8 to 1.4 V in 1.0 × 10-2 m NaCl solution, while the charge efficiency stabilizes at ≈80%. After 20 cycles, the capacitance retained is 64.27%, which is due to the irreversibility of Co2+/Co3+ and Mn2+/Mn3+ and the release of Ni3+ from the Ni-Co-Mn-O electrode after long desalination/salination cycles.

Preparation and electrochemical properties of a novel porous Ti/Sn-Sb-RuO x /β-PbO2/MnO2 anode for zinc electrowinning

MnO₂ coatings prepared in a sulfate system (S-MnO₂) and MnO₂ prepared in a nitrate system (N-MnO₂) were successfully deposited on porous Ti/Sn-Sb-RuO _x /β-PbO₂ substrates by electrodeposition, and their electrochemical properties were studied in detail. The bath composition plays a very important role in the MnO₂ coating prepared by electrodeposition at a low current density. The results of scanning electron microscopy show that a Ti/Sn-Sb-RuO _x /β-PbO₂/MnO₂ electrode has a rough morphology and the unit cell is very good. At the same time, the surface cracks in the S-MnO₂ coating are larger than those in the N-MnO₂ coating. In addition, the N-MnO₂ coating is composed of a fluffy sheet-like substance. The surface morphology of the N-MnO₂ coating is denser than that of the S-MnO₂ coating. The S-MnO₂ coating consists of irregularly stacked granular particles. Further, the main crystal phase of MnO₂ is γ type, and the main valence state of MnO₂ is +4. The results show that the oxygen evolution potential of the N-MnO₂ electrode is 63 mV lower than that of the S-MnO₂ electrode, indicating that the N-MnO₂ electrode has better oxygen evolution activity and electrochemical stability, which can also be confirmed by EIS test results. Under the accelerated life test conditions, the N-MnO₂ electrode has a better service life of 77 h at a current density of 1 A cm^-2 in 150 g L^-1 H₂SO₄ and 2 g L^-1 Cl^- solution.

Bio-Based Plasticized PVA Based Polymer Blend Electrolytes for Energy Storage EDLC Devices: Ion Transport Parameters and Electrochemical Properties

This report shows a simple solution cast methodology to prepare plasticized polyvinyl alcohol (PVA)/methylcellulose (MC)-ammonium iodide (NH₄I) electrolyte at room temperature. The maximum conducting membrane has a conductivity of 3.21 × 10^-3 S/cm. It is shown that the number density, mobility and diffusion coefficient of ions are enhanced by increasing the glycerol. A number of electric and electrochemical properties of the electrolyte-impedance, dielectric properties, transference numbers, potential window, energy density, specific capacitance (C_s) and power density-were determined. From the determined electric and electrochemical properties, it is shown that PVA: MC-NH₄I proton conducting polymer electrolyte (PE) is adequate for utilization in energy storage device (ESD). The decrease of charge transfer resistance with increasing plasticizer was observed from Bode plot. The analysis of dielectric properties has indicated that the plasticizer is a novel approach to increase the number of charge carriers. The electron and ion transference numbers were found. From the linear sweep voltammetry (LSV) response, the breakdown voltage of the electrolyte is determined. From Galvanostatic charge-discharge (GCD) measurement, the calculated C_s values are found to drop with increasing the number of cycles. The increment of internal resistance is shown by equivalent series resistance (ESR) plot. The energy and power density were studied over 250 cycles that results to the value of 5.38-3.59 Wh/kg and 757.58-347.22 W/kg, respectively.

Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors

To meet the charging market demands of portable microelectronics, there has been a growing interest in high performance and low-cost microscale energy storage devices with excellent flexibility and cycling durability. Herein, interdigitated all-solid-state flexible asymmetric micro-supercapacitors (A-MSCs) were fabricated by a facile pulse current deposition (PCD) approach. Mesoporous Fe2O3 and MnO2 nanoflakes were functionally coated by electrodeposition on inkjet-printed graphene patterns as negative and positive electrodes, respectively. Our PCD approach shows significantly improved adhesion of nanostructured metal oxide with crack-free and homogeneous features, as compared with other reported electrodeposition approaches. The as-fabricated Fe2O3/MnO2 A-MSCs deliver a high volumetric capacitance of 110.6 F cm-3 at 5 μA cm-2 with a broad operation potential range of 1.6 V in neutral LiCl/PVA solid electrolyte. Furthermore, our A-MSC devices show a long cycle life with a high capacitance retention of 95.7% after 10 000 cycles at 100 μA cm-2. Considering its low cost and potential scalability to industrial levels, our PCD technique could be an efficient approach for the fabrication of high-performance MSC devices in the future.

Fabrication of Co3O4 from Cobalt/2,6-Napthalenedicarboxylic Acid Metal-Organic Framework as Electrode for Supercapacitor Application

In this study, cobalt-based metal-organic framework (MOF) powder was prepared via the solvothermal method using 2,6-naphthalenedicarboxylic acid (NDC) as the organic linker and N,N-dimethylformamide (DMF) as the solvent. The thermal decomposition of the pristine cobalt-based MOF sample (CN-R) was identified using a thermogravimetric examination (TGA). The morphology and structure of the MOFs were modified during the pyrolysis process at three different temperatures: 300, 400, and 500 °C, which labeled as CN-300, CN-400, and CN-500, respectively. The results were evidenced via field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The crystallite size of all samples was calculated using Scherrer's equation. The smallest crystallite size of 7.77 nm was calculated for the CN-300 sample. Fourier transform infrared spectroscopy (FTIR) spectra were acquired for all the samples. The graphical study of the cyclic voltammogram (CV) gave the reduction and oxidation peaks. The charge transfer resistance and ionic conductivity were studied using electrical impedance spectroscopy (EIS). The galvanostatic charge-discharge (GCD) responses of all samples were analyzed. The relatively high specific capacitance of 229 F g-1 at 0.5 A g-1 was achieved in the sample CN-300, whereby 110% of capacitance was retained after 5000 cycles. These findings highlighted the durability of the electrode materials at high current densities over a long cycle.

Synergistic effect of hierarchical nanopores in Co-doped cobalt oxide 3D flowers for electrochemical energy storage

Hybridizing hierarchical porous transition oxides composed of nanoscale building blocks is highly desirable for improving the electrochemical performance of energy storage. Herein, we contribute a fabrication of novel hierarchically nanoporous flower-shaped metal/transition oxide (Co/Co3O4-CoO) with controllable three-dimensional structure. The designed Co/Co3O4-CoO 3D flowers (3DFs) are made of petal-shaped nanoporous Co3O4-CoO nanosheets with tunable pore sizes, in which metallic Co nanoparticles tend to attach to the edge of larger ones. The hierarchically nanoporous 3DFs with bimodal pore size distribution and higher fraction of small nanopores exhibit a higher specific capacitance (902.3 F g-1 at current density of 2 A g-1) and better cyclability than the uniformly nanoporous 3DFs with unimodal pore size distribution and larger BET surface area. The enhanced capacitance is mainly derived from the synergistic effect of hierarchical nanopores, in which large nanopores disproportionately facilitate osmotic solution flux and diffusive solute transport, whilst small nanopores supply faster channels for electron transportation and ion diffusion. Our work should provide a strategy to fabricate a smart functional hierarchical nanoporous architecture with 3DF structures for the development of electrochemical energy storage materials.

Potential Application of Ionic Liquids for Electrodeposition of the Material Targets for Production of Diagnostic Radioisotopes

An overview of the reported electrochemistry studies on the chemistry of the element for targets for isotope production in ionic liquids (ILs) is provided. The majority of investigations have been dedicated to two aspects of the reactive element chemistry. The first part of this review presents description of the cyclotron targets properties, especially physicochemical characterization of irradiated elements. The second part is devoted to description of the electrodeposition procedures leading to obtain elements or their alloys coatings (e.g., nickel, uranium) as the targets for cyclotron and reactor generation of the radioisotopes. This review provides an evaluation of the role ILs can have in the production of isotopes.

"Water-in-salt" electrolyte enhanced high voltage aqueous supercapacitor with carbon electrodes derived from biomass waste-ground grain hulls

To design high specific surface area and optimize the pore size distribution of materials, we employ a combination of carbonization and KOH activation to prepare activated carbon derived from ground grain hulls. The resulting carbon material at lower temperature (800, BSAC-A-800) exhibits a porous structure with a high specific surface area of 1037.6 m2 g-1 and a pore volume of 0.57 m3 g-1. Due to the synergistic structural characteristics, BSAC-A-800 reveals preferable capacitive performance, showing a specific capacitance as high as 313.3 F g-1 at 0.5 A g-1, good rate performance (above 73%), and particularly stable cycling performance (99.1% capacitance retention after 10 000 cycles at a current density of 10 A g-1). More importantly, the assembled symmetric supercapacitor using a water-in-salt electrolyte (17 m NaClO4) with high discharge specific capacitance (59 F g-1 at 0.5 A g-1), high energy density (47.2 W h kg-1) and high voltage (2.4 V) represents significant progress towards performance comparable to that of commercial salt-in-water electrolyte supercapacitors (with discharge specific capacitance of 50 F g-1, energy densities of ∼28.1 W h kg-1 and voltages of 2.0 V).