High Capacitance Value Research Articles

Tailored solution combustion method for enhancing high voltage electrochemical performance Li1.2Ni0.1Mn0.6Co0.1O2 as cathode material for lithium-ion batteries

The Lithium and Manganese-rich layered oxides with the formula Li1.2Ni0.1Mn0.6Co0.1O2 (LMR-NMC) are considered the most promising cathode materials for next-generation lithium-ion batteries due to their high energy densities, low cost, high thermal stability, and environmental safety. This paper reports the synthesis of LMR-NMC oxides in the presence of glycine-urea or citric acid-urea as surface modifiers for LMR-NMC-A and LMR-NMC-B, respectively using the solution combustion technique. The crystal structures of LMR-NMC-A and LMR-NMC-B samples were confirmed to have Hexagonal α-NaFeO2 structures in the R-3m space group. The HRSEM images reveal two different morphologies of the samples; Nano platelet (LMR-NMC-A) and Cubic-like (LMR-NMC-B). The cyclic voltammetric studies (CV) performed at a low scan rate value of 0.1 mV s−1 and a potential window of 2.0–5.0 V confirm the formation of the irreversible Li2MnO3 phase above 4.8 V in the first cycle and the presence of three redox peaks corresponding to Ni2+/Ni4+, Co2+/Co3+, and Mn3+/Mn in the subsequent cycles. The electrochemical properties of LMR-NMC-A and LMR-NMC-B electrodes demonstrated an initial discharge-specific capacity of 325.21 mAh g−1 and 300 mAh g−1, respectively, in a potential range between 2.0 and 5.0 V at a 0.1C rate. A comparison of the electrochemical properties of both morphologies of LMR-NMC revealed that the Nanoplatelet-like (LMR-NMC-A) sample performs better than the cubic-like (LMR-NMC-B) sample. The Nanoplatelet-like layered oxide demonstrated a high specific capacity of 180 mAh g−1 at a 1C rate and a high Coulombic efficiency of 86% after 200 cycles. BET indicates that LMR-NMC-A has a significantly higher surface area and substantial pore volume than LMR-NMC-B, addressing high voltage working capability, low voltage fading, and high specific capacitance values to a greater extent. These findings confirm the suitability of LMR-NMC-A as a cathode material for lithium-ion batteries used in high-load appliances and heavy vehicles.

Uranium-based electrode material for the high-performance supercapacitors

In recent decades, significant progress has been made in the engineering of electrode materials for supercapacitors. In this regard, the primary emphasis has been on investigating carbonaceous based materials. However, this focus has restricted the overall capacitance of supercapacitor devices, thus hindering their broader application possibilities. There is still a gap in the literature on high-performance radioactive element-based electrode materials. Bearing this, in this work, a simple approach was suggested for the implementation of uranium, as a radioactive element, decorating onto carbon architecture, as electrode material in high-energy supercapacitor cells. Herein, a facile pathway for tailoring a uranium-decorated graphene oxide nanostructure (U-GOx; where x stands for the GO:U ratio by weight) was proposed and the potential applications of the synthesized nanoarchitectures as an electrode material of supercapacitor cell were investigated. As per the author's knowledge, for the first time in the ever-burgeoning field of energy storage systems, a radioactive compound-based supercapacitor cell was fabricated. The physicochemical characterizations confirmed the successful anchoring of uranium atoms onto the graphene oxide skeleton. The U-GO5 electrode-based-supercapacitor cell offered the highest performance metrics with a 95.92 % capacitance retention value at the end of the 15,000 consecutive galvanostatic charge-discharge cycles, besides the high specific capacitance value of 258.6 F⸱g−1 at a high current density value of 10.0 A⸱g−1. Moreover, the radioactivity measurements were conducted to investigate whether the fabricated supercapacitors were radioactive or not. The results revealed that the measured radiation dose of the U-GO5-based supercapacitor cell before the GCD cycles, which was of the highest uranium content, was ca.0.06 μSv (the background measurement was excluded). This finding indicated there would be no adverse effect on human health or the environment. It can be speculated that this work is a new era for engineering a high-performance supercapacitor based on organic electrodes decorated with a radioactive element.

Two-step pyrolysis-hydrothermal synthesis of hierarchical nickel‑cobalt phosphate nanoflakes decorated on g-C3N4 nanosheets for high-performance hybrid supercapacitors

Ni-Co phosphate (NCP) nanoflakes and graphitic carbon nitride (g-CN) nanosheets are combined to fabricate a composite electrochemical electrode via a two-step pyrolysis-hydrothermal process. Physicochemical characterizations reveal the proper formation of the target material with highly porous morphology and crumpled nanostructures with highly active surface sites. The electrochemical properties of the NCP/g-CN composite in a three-electrode system depict excellent pseudocapacitive performance due to the faradaic behavior and redox activities of both NCP and g-CN with a very high capacitive value of 2000 F/g (242 mAh/g) @ 1 A/g current density. The charge storage behavior is mainly dominated by the surface-controlled (capacitive) process at higher scan rates, which is mostly dominated by surface pseudocapacitance, whereas, at low scan rates both surface-controlled and diffusion-controlled processes are equally active to provide a combined battery-capacitor behavior. Due to this, a hybrid supercapacitor device, fabricated with NCP/g-CN as positive and activated carbon (AC) as a negative electrode, showed excellent energy density (50 Wh/kg) along with exceptional cyclability (∼90 % capacity retention over 5000 cycles). Additionally, the redox-rich g-CN matrix within the composite dominates the sluggish diffusion-controlled process at higher scan rates to enhance the capacitive process without compromising the charge storage kinetics, thus enhancing the power density to ∼7.0 kW/kg. This excellent energy-power performance of the NCP/g-CN//AC hybrid supercapacitor cell (HSC) is better than some of the commercial devices like lead-acid, Ni-Cd, and Ni-MH batteries, indicating potential applications in next-generation charge storage devices.

Directed morphology engineering of 2D MoS2 nanosheets to 1D nanoscrolls with enhanced hydrogen evolution and specific capacitance

1D-molybdenum disulfide (MoS2) nanoscrolls displayed enhanced electrochemical properties compared to 2D-MoS2 nanosheet counterparts. Rolling of nanosheets is the main fabrication route to nanoscrolls. However, owing to the conflict between chemical stability and multiple bending, the morphology transition from nanosheets to nanoscrolls is quite challenging. Herein we describe a reversible morphology transition from nanosheets to nanoscrolls by utilizing non-covalent interactions between MoS2 nanosheets and phenothiazine based organic dye. Interestingly, nanoscrolls can easily be opened back into nanosheets by destroying the non-covalent interactions with organic solvents. The prepared nanoscrolls exhibited enhanced electrochemical properties than nanosheets. Compared to nanosheets, nanoscrolls exhibited comparatively lower overpotential with a Tafel slope of 141 mV dec-1 and high specific capacitance of 1868 F g−1. Hydrogen evolution by the Volmer-Heyrovsky mechanism being superior for the nanoscrolls is envisaged by the relatively increased availability of Hads sites at MoS2 edges induced by scrolling. Whereas the high specific capacitance value of nanoscrolls is ascribed to the enhanced electrical double-layer capacitance mediated charge storage, which arises due to the synergistic effect of both scrolled structure and the electron-rich phenothiazine-based dye.

A Hybrid Supercapacitor from Nickel Cobalt Sulfide and Activated Carbon for Energy Storage Application

Nickel–cobalt sulfide is a promising material for supercapacitor positive electrodes due to its high theoretical capacitance. Herein, the electrochemical properties of nickel–cobalt sulfide nanostructures synthesized via a two‐stage hydrothermal method are investigated and the synthesis conditions to achieve high mass loading while maintaining high specific capacitance are determined. The nanostructural morphology and effective mass loading of the electrodes (≈10 mg cm−2) enable the achievement of a high specific capacitance value of 8.1 F cm−2 at a current density of 5 mA cm−2. A hybrid capacitor is made using optimized nickel–cobalt sulfide electrodes as the positive electrode and activated carbon as the negative electrode. The device exhibits a maximum operation potential window of 1.75 V and an energy density of 51.2 Wh kg−1 at a power density of 262.5 W kg−1. Electrochemical measurements demonstrate that the device maintains a capacitance retention rate of 95% after 10 000 charge–discharge cycles within a working voltage of 1.8 V. High electrochemical performances compared with others devices‐based water electrolytes make it promising for the energy storage device.

CO2-Derived Nanocarbons with Controlled Morphology and High Specific Capacitance.

The conversion of CO2 to nanocarbons addresses a dual goal of harmful CO2 elimination from the atmosphere along with the production of valuable nanocarbon materials. In the present study, a simple one-step metallothermic CO2 reduction to nanocarbons was performed at 675 °C with the usage of a Mg reductant. The latter was employed alone and in its mixture with ferrocene, which was found to control the morphology of the produced nanocarbons. Scanning electron microscopy (SEM) analysis reveals a gradual increase in the amount of nanoparticles with different shapes and a decrease in tubular nanostructures with the increase of ferrocene content in the mixture. A possible mechanism for such morphological alterations is discussed. Transmission electron microscopy (TEM) analysis elucidates that the nanotubes and nanoparticles gain mainly amorphous structures, while sheet- and cloud-like morphologies also present in the materials possess significantly improved crystallinity. As a result, the overall crystallinity was preserved constant for all of the samples, which was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Finally, electrochemical tests demonstrated that the prepared nanocarbons retained high specific capacitance values in the range of 200-310 F/g (at 0.1 V/s), which can be explained by the measured high specific surface area (650-810 m2/g), total pore volume (1.20-1.55 cm3/g), and the degree of crystallinity. The obtained results demonstrate the suitability of ferrocene for managing the nanocarbons' morphology and open perspectives for the preparation of efficient "green" nanocarbon materials for energy storage applications and beyond.

Electrochemical performance of diazonium-generated carbon films for electrochemical double-layer capacitors (EDLCs)

Carbon-based electrode materials for energy storage systems have received considerable attention thanks to their excellent mechanical properties, large specific surface areas and moderate electrical conductivities. Here, diazonium-generated carbon films on the flexible carbon paper (CP) electrodes were prepared through electrochemical reduction of aryl diazonium salts bearing COOH, NO2, CH3 and H functional groups. The production of polymeric carbon films by diazonium modification method was preferred because it is a simple and effective process, and also the carbon-based films prepared by this method are covalently attached to the carbon electrode surfaces. The capacitive properties of the robust carbon films were assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in three-electrode and asymmetric device configurations. The results indicated that diazonium-generated carbon films on flexible substrates exhibited typical EDLC behavior with high specific capacitance values (237.6–446.9 F g−1 at 0.5 A g−1 current density), and also their capacitive performances were largely dependent upon the functional groups on the benzene ring. Overall, this work reveals that the diazonium modification method is a promising approach to create the carbon-based active electrode materials in advanced energy-storage systems.

Cheese-like hierarchical porous carbon material with large specific surface area derived from red dates for high performance supercapacitors

Red dates are rich in porous structure inside, and the carbonization process can easily inherit unique constructions, which is beneficial to the rapid transmission of ions. The specific surface area (SSA) and pore structure are the key factors that determine the energy storage performance of carbon material supercapacitors. In this paper, hierarchical porous carbon materials (RDKC-4-800) with cheese-like microstructure based on red dates were prepared by two steps of hydrothermal pre-carbonization and KOH carbonization activation. The obtained materials have a rich hierarchical pore structure and large SSA (1115.7 m2 g−1), which is conducive to ion and electron transport and contribute to excellent electrochemical properties. Electrochemical tests indicate a high specific capacitance value of 341.9 F g−1 for the material at a current density of 0.5 A g−1. The assembled supercapacitors exhibited an energy density of 10.9 W h kg−1 and a power density of 124.93 W kg−1, outperforming many biomass carbon supercapacitors studies under similar conditions reported in the literature. After 30,000 charge and discharge cycles at a current density of 5 A g−1, the capacitance retention rate is 81.29 % and the coulombic efficiency is 99.67 %. This study provides an efficient and concise method to prepare red dates porous carbon materials and demonstrates that red dates biomass can be effectively reused in the field of supercapacitors.

Polyaniline-MXene composite electrode with excellent electrochemical properties for all-solid flexible supercapacitors

In this paper, MXene based electrode active materials and MXene cross-linked polyacrylic acid hydrogel electrolytes with high cycling performance and high specific capacitance have been successfully prepared. Polyaniline with high capacitance values has been grown on the MXene surface by in situ polymerization, which can significantly improve electrochemical properties. As the MXene surface is rich in functional groups, it can be used as a nucleation site for in situ polymerization of aniline monomers deposited. The PANI filled with MXene forms a 3D porous conductive network reducing the self-stacking of MXene and providing a large number of channels for electrolyte ions to enter MXene. The supercapacitor has been tested and assembled with good flexibility and the specific capacitance has risen to 222 F g−1. The capacitance retention of 98.5 % after 10,000 charges and discharges is due to the improved performance of the composite material and the excellent stability of the gel electrolyte and electrodes. The above results show that the prepared electrodes and devices have promising applications in flexible wearable devices.

Copolymer versus bilayer composite: Electrochemical, electrochromic and capacitive properties of benzotriazole and edot containing conjugated polymers

In this study, benzotriazole-based homopolymer (P-TBtz), copolymer (C-TBtzEdot), and bilayer composites (B-TBtzEdot and B-EdotTBtz) were prepared by electrochemical polymerization. B-TBtzEdot and B-EdotTBtz differ only in the sequential deposition orders onto the ITO electrode. Wise selected materials successfully performed their jobs: TBtz introduced a multichromic property to polymer films and Edot improved the charge storage capacity. Electrochemical characterizations of resulting conjugated polymer films were performed by cyclic voltammetry (CV), chronopotentiometry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). For optical and morphological characterization, UV–vis spectroscopy and scanning electron microscopy (SEM) were used, respectively. According to SEM images, all films have different morphologies. Moreover, upon applied potential, change in the absorption spectra and color change was monitored. Besides, the capacitance value of the polymer films was calculated from cyclic voltammogram and galvanostatic charge-discharge curves. C-TBtzEdot had the highest capacitance value as 97.5 F/g at 2 mV/s and 92 F/g at 0.5 A/g.

Binder-Free NiS@PPy Nanocomposite Cathode for High-Performance Supercapacitors

Industrialization and the increase in the world population increase the need for energy.Supercapacitors are preferred because of their features such as high specific power, long life, environmentalfriendliness, fast charge, and discharge rates. Supercapacitors are divided into two categories as EDLC andpseudo capacitors. Pseudo capacitors use materials that exhibit pseudo capacitance, such as transition metaloxides/sulphides and conductive polymers. Electrochemical studies and synthesis methods of polymerbased metal oxide composites, polyaniline and polypyrrole are examined in detail. Evaluating the variousmethods used in the preparation of supercapacitor electrodes, an idea is presented on the selection ofsuitable materials for electrochemical applications. Conductive polymers have good capacitance behaviorbut low cyclic stability. Transition metal sulfides exhibit electrochemical performance with highcapacitance values and excellent redox reversibility. This study investigates NiS/PPy polymer assupercapacitor electrode material. The NiS structure was synthesized using Na2S and nickel foam. NiS-PPycoating was carried out by electrochemical coating method. Structures were characterized by XRD andSEM, electrochemical studies such as cyclic voltammetry (CV), galvanostatic discharge (GCD) werecarried out. By incorporating NiS into the PPy matrix, the C value was increased from 22.22 to 1404 F g-1

PPy@MWCNT Nanocomposite for Supercapacitor Applications

Polypyrrole (PPy) is a potential electrode material for supercapacitors due to its properties suchas high conductivity and chemical stability. However, additional additives can be used to further improvethe capacity values and energy storage performance of PPy. Multi-walled carbon nanotubes (MWCNT) arenanomaterials with properties such as high surface area, excellent conductivity and mechanical strength,and can improve supercapacitor performance when integrated into the PPy matrix. In this study, synthesis,characterization and performance analysis were performed to evaluate the potential of PPy and MWCNTdoped PPy in supercapacitor applications. PPy and MWCNT doped PPy were characterized using analyticaltechniques such as XRD (X-ray diffraction) analysis and SEM (scanning electron microscopy) imaging.XRD analysis was used to determine the crystal structures and crystal sizes of the material and showed thatthe crystal structures of PPy and MWCNT doped PPy were preserved. SEM imaging was used to examinethe surface morphology of the material and it was observed that it has a homogeneous surface structure.Supercapacitor performance was evaluated using electrochemical characterization methods. PPy andMWCNT doped PPy samples exhibited high capacitance values and fast charge-discharge properties. Theintegration of the MWCNT additive into the PPy matrix allowed the electrode to maintain its chemicalstability while increasing the surface area. These results show that PPy and MWCNT doped PPy have thepotential to provide more efficient energy storage in supercapacitors.

Interconnected Vanadyl Pyrophosphate Nanonetworks as a Flexible Electrode for High-Voltage and Long-Life Li-Ion Supercapacitors.

Engineering vanadium-based materials with high conductivity, superior redox performance, and high operating voltage has attracted widespread attention in energy storage devices. Herein, we demonstrated a simple and feasible phosphorization technique to design three-dimensional (3D) network-like vanadyl pyrophosphate ((VO)2P2O7) nanowires on flexible carbon cloth (CC) (VP-CC). The phosphorization process enabled the VP-CC to increase the electronic conductivity, and the interconnected nano-network of VP-CC opens pathways for fast charge storage during the energy storage processes. Specifically, the 3D VP-CC electrodes and LiClO4 electrolyte designed as a Li-ion supercapacitor (LSC) demonstrate a maximum operating window of 2.0 V with a superior energy density (Ed) of 96 μWh cm-2, power density (Pd) of 10,028 μW cm-2, and outstanding cycling retention (98%) even after 10,000 cycles. In addition, a flexible LSC assembled utilizing VP-CC electrodes with a PVA/Li-based solid-state gel electrolyte exhibits a high capacitance value of 137 mF cm-2 and excellent cycling durability (86%) with a high Ed of 27 μWh cm-2 and Pd of 7237 μW cm-2. Considering excellent energy storage features, the highly conductive vanadium-based material has been utilized as an ideal electrode for various flexible/wearable energy storage devices with superior performance.

Study on the Application of Nitrogen-Doped Holey Graphene in Supercapacitors with Organic Electrolyte.

We present a facile low-cost method to produce nitrogen-doped holey graphene (N-HGE) and its application to supercapacitors. A composite of N-HGE and activated carbon (AC) was used as the electrode active material in organic-electrolyte supercapacitors, and the performances were evaluated. Melamine was mixed into graphite oxide (GO) as the N source, and an ultra-rapid heating method was used to create numerous holes during the reduction process of GO. X-ray photoelectron spectra confirmed the successful doping with 2.9-4.5 at.% of nitrogen on all samples. Scanning electron micrographs and Raman spectra revealed that a higher heating rate resulted in more holes and defects on the reduced graphene sheets. An extra annealing step at 1000 °C for 1 h was carried out to further eliminate residual oxygen functional groups, which are undesirable in the organic electrolyte system. Compared to the low-heating-rate counterpart (N-GE-15), N-HGE boosted the specific capacity of the supercapacitor by 42 and 22% at current densities of 0.5 and 20 A/g, respectively. The effects of annealing time (0.5, 1, and 2 h) at 1000 °C were also studied. Longer annealing time resulted in higher capacitance values at all current densities due to the minimized oxygen content. Volumetric specific capacitances of 49 and 24 F/cm3 were achieved at current densities of 0.5 and 20 A/g, respectively. For the high-power-density operation at 31,000 W/kg (or 10,000 W/L), an energy density as high as 11 Wh/kg (or 3.5 Wh/L) was achieved. The results indicated that N-HGE not only improved the conductivity of the composite supercapacitors but also accelerated ion transport by way of shortened diffusion paths through the numerous holes all over the graphene sheets.

Fabrication of NiMn2O4 nanospheres and its hybrid with polyaniline for high energy and high power supercapacitor with long cycle stability

NiMn2O4 nanospheres have been prepared by a solution combustion method and hybridised with polyanilne by the dilute polymerization method. The metal oxide and its polymer hybrid forms were characterized by several physicochemical methods and microscopic techniques. The capacitive nature and cyclic stability were studied by cyclic voltammetry and galvanostatic charge–discharge measurements. The newly fabricated NiMn2O4 nanospheres and PANI-NiMn2O4 nanohybrid showed high specific capacitance values of 374 Fg−1 and 442 Fg−1 respectively, at the scan rate of 10 mVs−1. The NiMn2O4 nanospheres showed enhanced energy density (13.8 WhKg−1) compared to its hybrid form (2.82 WhKg−1). However, the power density of the PANI-NiMn2O4 nanohybrid (565.2 Wkg−1) was found to be higher than that of the pure NiMn2O4 nanospheres (447.18 WKg−1). In addition to that, both the electrode materials showed the same columbic efficiency (∼96 %) after 1000 consecutive cycles.

Silver-doped reduced graphene oxide/Pani composite synthesis and their supercapacitor applications

In this study, graphene oxide was synthesized by the Hummers method. Reduced graphene oxide was obtained by the hydrothermal method. Then, silver-doped Reduced Graphene Oxide/Polyaniline (Ag-doped rGO/PANI) composites were synthesized. Some physical analyzes of the synthesized composite materials were made. In the XRD examination, it was understood that the materials generally have polyaniline properties. Electrochemical properties were investigated with electrodes prepared from these composites. Specific capacitance, energy, and power density values were calculated from these measurements. The specific capacitance was measured in the range of 0.5–30 A/g and the highest capacitance value was found to be 379 F/g. From these results, the material containing approximately 17 mass percent silver doped reduced graphene oxide gave better results among composite materials. This composite was the most stable material with results of 286–317 F/g at all applied currents. In addition, a coin cell application was made for this example and its measurements were taken.

Enhanced magnetic, electrochemical and gas sensing properties of cobalt substituted nickel ferrite nanoparticles prepared by hydrothermal route

The cobalt doped nickel ferrite nanoparticles were successfully synthesized via hydrothermal method at low reaction temperature. X-ray diffraction analysis confirmed the cubic spinel structure with an average crystallite size of 41 nm for pure nickel ferrite (NF) and in the range (38–33) nm for substituted samples. High resolution transmission electron microscope observations revealed the cubic-like shaped nanosized particles. Ultraviolet diffuse reflectance spectroscopy indicated an increase in the energy bandgap with increasing Co content. X-ray photoelectron spectroscopy confirmed the oxidation states of constituents, +2 for Ni, +2 for Co, and +3 for Fe. The AC conductivity was enhanced with increasing frequency. The observed higher value of saturation magnetization and coercivity, manifests its suitability in high density recording media. Besides, the ratio of Hcr/Hc confirmed the pseudosingle domain nature of the synthesized nanoparticles. The valency and occupancy of the Fe ion in tetrahedral-A and octahedral-B sites within the spinel cubic structure were elucidated by Mossbauer spectroscopy analysis. The cyclic voltammetry (CV) studies revealed the pseudocapacitance behaviour with high specific capacitance value at low scan rates. The sensor activity towards liquified petroleum gas (LPG) at 100 ppm showed the response and recovery time as 52 and 13s respectively.

A two-pronged strategy to modulate the porosity of porous carbons for capacitors: The relative effects of the texture and fuel properties of carbonaceous matter

Based on the search for a novel method to modulate the texture properties of porous carbon, it is essential to demonstrate the relative influence of texture and fuel properties (i.e., the general term of volatile, fixed carbon, ash, elements, and calorific value) of carbonaceous matter. Herein, H3PO4 activation was applied to fabricate pine sawdust-derived porous carbons (PC-T; T can be 450, 500, 550, and 600) with various fuel and texture properties. Afterward, the pore architectures recorded for PC-T were adjusted using the CO2 activation procedure; that is, PC-T-derived porous carbons (PC-TC) were obtained. PC-TC showed a significant increase in texture properties (e.g., specific surface area and total pore volume) and specific capacitance compared to PC-T. In the three-electrode configuration, PC-550C achieved high specific capacitance values (e.g., 230.78 F/g at 0.5 A/g). The assembled PC-550C-based symmetrical supercapacitor achieved an impressive specific capacitance of 172.12 F/g upon 0.5 A/g. Interestingly, it equally delivered high energy density (23.91 Wh kg−1) and power density (47.30 kW kg−1), respectively. Further, the specific surface area of the PC-TC samples depends not only on the fuel properties of the PC-T samples but also on the texture properties of the PC-T samples. Superior fabricability and variable texture properties enable the two-pronged strategy (i.e., sequential H3PO4–CO2 activation) for producing bulk senior and multi-level porous carbons.

Ag nanoparticles anchored reduced graphene oxide sheets@nickel oxide nanoflakes nanocomposites for enhanced capacitive performance of supercapacitors

In this work, ternary nanocomposite of silver nanoparticles embedded on the surface of few layered reduced graphene oxide coated nickel oxide (Ag-rGO@NiO) was successfully fabricated as electrode material for high performance supercapacitor applications. NiO nanoflakes was prepared by hydrothermal route while coating of few layered rGO and subsequent silver anchoring was done by chemical methodology. The morphological analysis by scanning electron microscopy and transmission electron microscopy showed NiO nanoflakes coated by rGO/distributed on rGO substrate with scattered Ag nanoparticles. The elemental composition and distribution was confirmed by energy-dispersive X-ray (EDX) and Raman spectroscopy. The electrochemical measurements showed that the fabricated electrode of Ag-rGO@NiO is suitable electrode material and can enhance the capacitive performance of supercapacitors due to its high capacitive value (1230 Fg−1) in contrast to the binary rGO@NiO (337.5 F g−1) and bare NiO flakes (145 F g−1) at current density of 1 A g−1. The enhancement in the capacitive value of Ag-rGO@NiO composite was mainly attributed to the highly conductive rGO sheets and Ag nanoparticles where rGO sheets provided conductive path and Ag created new channels for the electron transfer. Furthermore, it also showed excellent cyclic stability as it retained 88.5 % of its initial capacitive value even after 3000 cycles as well as showed excellent energy density of (27.33 Wh kg−1) at power density (200.073 W kg−1).

Synergistic effects of multifunctional nanostructured WO3-WS2 decorated on polypyrrole (WO3-WS2/PPy) for the removal of toxic heavy metals from wastewaters and high supercapacitor performance

Nowadays, developing a simple, economic, and scalable approach for environmental remediation and producing energy storage devices remains challenging. Herein, we report a novel WO3–WS2 decorated polypyrrole (WO3–WS2/PPy) nanocomposite for the removal of heavy metals, i.e., Cd(II) and Ni(II) and high-performance supercapacitor electrodes.The WO3–WS2/PPy showed significant improvement in the removal of Cd(II) (95.33%) and Ni(II) (89.95%), while WO3–WS2 and PPy revealed removal efficiency of 87.02 and 77.01% for Cd(II) and 82.97 and 74.66% for Ni(II), respectively. For the competitive adsorption experiment, Cu2+/Zn2+ causes a significant influence, while Na+/K+/Mg2+/Ca2+ exerted less effect on the adsorption of the aforementioned metal ions. The WO3–WS2/PPy exhibited higher selectivity toward Cd2+ than Ni2+. Along with, the WO3–WS2 decorated PPy based electrode showed a high specific surface area and support conductive networks, which synergistically improved charge storage capability. The WO3-WS2/PPy-based electrodes exhibit superior electrochemical performance with excellent rate capability, offering the high specific capacitance value of 624 F/g at 3 A/g current density and retaining capacitance stability of 81% after 5000 cycles in 1 M Na2SO4 electrolyte solution. The outcomes of this research infer that WO3-WS2/PPy is a promising candidate for wastewater treatment and high-performance energy storage applications.