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The strategy of converting waste materials into new functional materials is a promising approach for energy-storage applications, particularly in the case of silver-impregnated activated carbon (SAC). SAC, which is typically derived from coconut shells, is primarily used for water purification in home-based filters due to its excellent antibacterial properties. However, the silver concentration is low, and it tends to leach out after a certain period, resulting in waste. To address this issue, SAC was used as a precursor for electrodes in supercapacitor applications. Additional surface treatments, such as heteroatom doping, are also being employed to improve the electrical conductivity and wettability of SAC. Nitrogen was introduced using urea as a precursor to enhance the properties of SAC. XRD analysis confirmed the structural analysis of activated carbon and nitrogen-activated carbon. Morphological analysis revealed the formation of micropores on the surface of the samples. FTIR analysis confirmed the presence of functional groups in the samples. Raman spectra showed the presence of defects after the introduction of nitrogen atoms into the carbon lattice, with higher relative $I_d/I_g$ compared to AC. Multipoint bet analysis was conducted, and the surface area of the sample was found to be approximately 815m²g${}^{-1}$, with pore sizes of 810m²g${}^{-1}$. Electrochemical analysis was carried out in both three- and two-electrode configurations. The specific capacitance of NAC in cyclic voltammetry and galvanostatic charge–discharge analysis was found to be higher than that of AC because the nitrogen atoms reduced the ionic charge transfer resistance between the electrode and electrolyte surface. Electrochemical impedance spectroscopy (EIS) was also conducted, confirming the solution resistance with 1.5Ohm.

Chemical reactions result from the outside shell electrons of the reacting species being shared in various types of combinations. Typical distances involved are tenths of nm, resulting in binding energies typically in the order of hundreds of kJ/mole (eV/atom). The synthesis of a novel “atomic system” formed from Iron and di-Hydrogen has been achieved. The measured enthalpy of formation is some 40 MJ/moleFe and the distance between the hydrogen proton and the iron nucleus is some 8 pm, hence the proposed name: Iron Pico-Hydride. This compound is a permanent electric dipole of atomic size. Pico-Hydrides could, thus, play a significant role in HT superconductivity and in super-capacitors. The synthesis is compatible with the standard model.

We present the design of a high-performance 2 V asymmetric supercapacitor made of graphene-based hybrid nanocomposites in 1 M KOH electrolyte. rGO-CNT-FeOOH (GC-F) was used as the cathode and rGO-CNC-MnO₂ (GC-M) as the anode. Both composites well balanced each other in the asymmetric device and gave a high electrochemical performance. The energy density of this ASC is 66.6 W h kg${}^{-1}$ at 3.8 kW kg${}^{-1}$ power density with an excellent capacitance retention of 88% after 3000 galvanostatic charge-discharge cycles.

In this work, MoS₂ was successfully deposited on Ni foam (NF) by a simple one-step electrochemical deposition method. MoS₂ were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectrum (XPS) and energy dispersive spectrometer (EDS). XRD and FESEM results show that MoS₂ is an amorphous film structure. The electrochemical properties of the MoS₂ electrode have been studied in detail via cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopic (EIS) technology, respectively. The MoS₂/NF binder-free electrode provides a special capacitance of 210 F/g at a constant discharge current density of 1 A/g. When the current density increases five times, the specific capacitance can still maintain 51.74% of the initial capacitance. In addition, after 1000 cycles at 3 A/g, the capacitance retention of the MoS₂ electrode still retained 79.4%.

ZnS nanoparticles (NPs) are prepared by co-precipitation method using ethylene diamine tetra-acetic acid as a stabilizer and capping agent. The structural, morphological and optical properties of as-synthesized NPs are investigated using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, ultraviolet-visible (UV-Vis) absorption, and photoluminescence spectroscopy. The X-ray diffraction pattern exhibits a zinc-blended crystal structure at room temperature. The particle size was found to be in the range of 22.22 nm. The ultraviolet absorption spectrum shows the blue shift in the bandgap due to the quantum confinement effect. The photoluminescence spectrum of ZnS NPs shows a blue visible spectrum. The template of the cyclic voltammetry contour demonstrated a strong rate suggesting that the ZnS nanostructure electrode has a reduced polarization effect. The above studies have provided resplendent efficiency and proven that ZnS NPs can be used as a prominent material for supercapacitor applications.

A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy supercapacitors can store is low and does not allow large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the high power amount needed to reach short refill times, a solution is proposed, which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power. In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power level, in order to achieve a fast energy transfer between two supercapacitive tanks.

The decrease of energy consumption per 1 bit processing (ε) and power supply voltage (V_dd) of integrated circuits (ICs) are long-term tendencies in micro- and nanoelectronics. In this framework, deep-sub-voltage nanoelectronics (DSVN), i.e., ICs of ~10¹¹–10¹² cm^-2 component densities operating near the theoretical limit of ε, is sure to find application in the next 10 years. In nanoelectronics, the demand on high-capacity capacitors of micron sizes sharply increases with a decrease of technological norms, ε and V_dd. Creation of high-capacity capacitors of micron size to meet the challenge of DSVN and related technologies is considered. The necessity of developing all-solid-state impulse micron-sized supercapacitors on the basis of advanced superionic conductors (nanoionic supercapacitors) is discussed. Theoretical estimates and experimental data on prototype nanoionic supercapacitors with capacity density δ_C ≈ 100 μF/cm² are presented. Future perspectives of nanoionic devices are briefly discussed.

Tin oxide thin films were prepared via spray pyrolysis method. The structural and morphological properties of SnO₂ thin films have been investigated using X-ray diffraction (XRD) and scanned electron microscope (SEM) analysis. The XRD pattern confirms the tetragonal rutile structure of SnO₂ with preferential orientation along (200) plane. SEM image reveals the nanocrystalline nature of the SnO₂ films. SnO₂ thin films were subjected to electrochemical tests to study the supercapacitor behavior. Maximum specific capacitance of 168 F/g at a scan rate of 25 mV/s was obtained using 0.5 M KOH as the electrolyte. This is the highest value ever reported for spray deposited tin oxide thin films.

Conducting polymer hydrogels represent a unique class of materials that possess enormous application in flexible electronic devices. In the present work, conducting carboxymethylcellulose (CMC)-co-polyacrylamide (PAAm)/polyaniline was synthesized by a two-step interpenetrating network solution polymerization technique. The synthesized CMC-co-PAAm/polyaniline with interpenetrating network structure was prepared by in situ polymerization of aniline to enhance conductivity. The molecular structure and morphology of the copolymer hydrogels were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The novel conducting polymer hydrogels show good electrical and electrochemical behavior, which makes them potentially useful in electronic devices such as supercapacitors, biosensors, bioelectronics, solar cells and memory devices.

The aim of this work is to synthesize nickel sulfide–graphene (NiS/G) nanocomposites with different compositions and to analyze the structural and electrochemical capacity and compatibility for their application as supercapacitor material with enhanced charge storage capacity and reduced impedance. NiS nanoparticles (NPs) loaded on graphene were synthesized at various concentrations of graphene by a simple hydrothermal route from nickel sulphate and graphene oxide as precursors in the presence of PVP as surfactant and thioacetamide (TAA) as sulfur source. The composites structural, morphological and physical properties were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier Transform-infrared (FT-IR) analysis. SEM measurements showed the presence of surface attachment of the NiS NPs onto the graphene sheets. To assess the properties of the nanocomposites for their applicability in supercapacitors, electrochemical analysis was carried out in 6M KOH electrolyte. Three different samples with different graphene contents — GNiS-10 with 10 wt.%, GNiS-20 with 20 wt.% and GNiS-40 with 40 wt.% were prepared. The specific capacitances obtained for the nanocomposites were calculated to be 84.33F/g, 129.66F/g, 187.53F/g at 10mV/s scan rate, respectively. The EIS data showed that the loading of NiS NPs on graphene caused the reduction in impedance at high frequency and has a long cycle life (over 1000 cycles).

A series of SnS/Graphene (SnS/G) nanocomposites at various concentrations of graphene were synthesized by a wet chemical route and the prepared composites were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HRTEM) for its structural and morphological investigation. Results show that the prepared SnS nanoparticles in the composite are $\sim$30nm sized and uniformly dispersed on graphene sheets. To test the supercapacitance behavior, electrochemical measurements were carried out in 6M KOH electrolyte. A maximum specific capacitance of 984F/g was observed for SnS/G-c at 5mVs${}^{-1}$ scan rate. Galvanostatic charge/discharge curves showed an excellent cyclic stability with higher charge/discharge duration, and hence could be used for high performance supercapacitor applications.

Incessant streak of unsuccessful attempts to synthesize low cost graphene with larger flake size and purity is frequently reported. Any reported methods that result in few layers of graphene with minimal contamination are definitive to exist. In this work, graphene was prepared economically from source of “paper” and detailed investigation was done on the effect of synthesizing parameters like paper source, temperature and amount of urea in the formation of graphene. This is a cost effective method, in which the paper that we use in our daily life was carbonized with the help of urea at a temperature of 850${}^{\circ }$C under N₂ atmosphere. The paper source was varied, shape of the paper was altered and the graphene paper with large surface area was synthesized without smudging and the prepared graphene paper was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) for its structural, morphological investigation. To test the supercapacitance performance, electrochemical behavior was investigated in 6M KOH electrolyte. The specific capacitance of 1122F/g was obtained at 5mV/s scan rate. Chronopotentiometry curves showed an excellent cyclic stability with higher charge/discharge duration and hence could be used for electrochemical supercapacitor applications.

This study’s objective is to prepare and characterize a ZnO-rGO composite for use in supercapacitors. The hydrothermal method was used to successfully prepare ZnO and ZnO-rGO. Characterization of the prepared materials was carried out using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and ultraviolet-visible (UV–Vis) spectrometers. The electrochemical properties of the ZnO and ZnO-rGO electrodes were examined using cyclic voltammetry (CV) and impedance spectroscopy. The specific capacitance of the ZnO-rGO composite electrode in 1M NaOH as an electrolyte was 293.37F/g at the scan rate of 5mV/s. As a result of the low equivalent series resistance and improved ion diffusion produced by ZnO and rGO working together, the ZnO-rGO nanoparticles electrode has a higher super capacitance. The result achieved a higher energy density of 39.93Wh/kg and a power density of 54.45kW/kg. These findings demonstrated the significance of rGO-based composites in the development of high-performance energy storage systems as well as their enormous potential for improvement.

Numerous are the ways through which phthalocyanines have been put into very good use. The on-going search for new energy storage and conversion systems has made phthalocyanines even prettier as alternatives to metal and metal oxide catalysts because of their lower cost. This review article looks through a very narrow window of the applications of phthalocyanines in batteries and supercapacitors as a means of improving the qualities such as cycle property, energy density, capacity, open circuit voltage, etc, of these devices.

This paper reports a new graphene oxide (GO)/acenaphthenequinone composite as efficient electrode in electrochemical supercapacitors. The nanosheets of GO provide high surface area and conductivity. The microneedle-like acenaphthenequinone contributes convincible specific capacitance. The structure and morphology of GO/acenaphthenequinone composite have been characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectra and Raman spectra. According to the cyclic voltammetry (CV), galvanostatic charge/discharge, impedance spectra and cycling life analyses, the GO/acenaphthenequinone composite exhibits brilliant supercapacitors performance with a specific capacitance of 248.7 F g^-1 at a scan rate of 1 mV s^-1 and enhanced stability of about 82% (147.5 F g^-1) of initial capacitance (179.8 F g^-1) after 500 cycles at a current density of 1 A g^-1.

Polyaspartic acid-based nitrogen-doped porous carbon (N-PC) has been prepared by one-step activation and carbonization of polyaspartic acid at 800${}^{\circ }$C in N₂ atmosphere. The morphologies and structures of products are characterized by X-ray diffraction, element analysis, scanning electron microscopy and N₂ adsorption–desorption. The characterizations show that the morphologies and structures of the N-PC deeply depend on the additive amount of activating agent. The as-prepared activated carbon possesses irregular surface morphology with high surface area in the range of 1600–1800m² g${}^{-1}$. Furthermore, the activated carbon possesses proper amount of micropore and mesopore structures. As an electrode material for supercapacitors, the specific capacitance of N-PC is as high as 265F g${}^{-1}$ at a current density of 0.5A g${}^{-1}$, and it also exhibits good cyclability (retains about 93% initial capacitance after 5000 cycles).

The ZnCo₂O₄ nanorods and nanosheets were grown on nickel foam by a facile and effective hydrothermal method, respectively. The effect of the morphologies of the nanostructures on electrochemical performance was investigated. Importantly, ZnCo₂O₄ nanorod electrodes with a high specific surface area exhibited a higher specific capacitance of 2457.4 F g${}^{-1}$ at 2 A g${}^{-1}$ and remarkable cycling stability with capacitance retention of 97.7% after 1000 cycles, which are superior to those of ZnCo₂O₄ nanosheet electrodes. Such a result is well explained. The investigation on the electrochemical properties of these two nanostructures as electrodes confirmed that the morphology of active materials has an important impact on electrochemical properties.

Porous NiCo₂S₄ networks have been successfully synthesized by a facile one-pot solvothermal method without the use of any surfactant or template. Crystal structure, morphology, composition and surface area of the as-synthesized samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmet–Teller techniques. Owing to their porous nature and small crystalline size, the as-prepared NiCo₂S₄ networks based supercapacitor electrodes showed a high specific capacitance of 1250F$\cdot$g${}^{-1}$ at 1A$\cdot$g${}^{-1}$, and excellent cycling stability with the retention capacity of 70.3% after 5000 cycles in the KOH aqueous solution electrolyte.

Nitrogen-enriched porous carbon materials have been successfully synthesized via a template carbonization method, in which nicotinic acid acts as carbon/nitrogen sources, and Ca(OAc)${}_2\cdot$H₂O as a template. It reveals that the mass ratio of Ca(OAc)${}_2\cdot$H₂O-to-nicotinic acid and the carbonization temperature dominate the morphology of carbon materials as well as capacitive performances. The sample obtained with the ratio of Ca(OAc)${}_2\cdot$H₂O-to-nicotinic acid as 1.5 at 800${}^{\circ }$C, namely the C-1.5-800 sample, displays the optimum capacitive behavior. It is amorphous with low-graphitization degree, possessing hierarchical porous structure, high nitrogen content (14.5%), large specific surface area (788m² g${}^{-1}$) and high total pore volume (3.56cm³ g${}^{-1}$). As a result, the as-made C-1.5-800 electrode exhibits a maximum specific capacitance of 216F g${}^{-1}$ at a current density of 1A g${}^{-1}$ in 6M KOH aqueous solution. It also displays a maximum energy density of 45.9Wh kg${}^{-1}$ at 2050W kg${}^{-1}$ and a maximum power density of 20100W kg${}^{-1}$ at 19.2Wh kg${}^{-1}$ at operation temperature of 50${}^{\circ }$C in [EMIm]BF₄/AN organic electrolyte. More importantly, the C-1.5-800 electrode exhibits an excellent cycling stability within 5000 cycles at 5A g${}^{-1}$. This work may enrich and broaden the field of porous carbon and its potential application for supercapacitors under high temperature.

As one of the electrode materials for supercapacitor, Co₃O₄/graphene composite was mainly synthesized via two-steps method. Here, a facile one-pot method was used for Co₃O₄/graphene composite, and the performances of one-pot-synthesized Co₃O₄/graphene composite were carefully investigated. Liquid-phase exfoliation was used for graphene and the $D$-band/$G$-band ratio of liquid-phase exfoliated graphene was only 0.094, which indicated that the graphene had low defect density and enhanced electrical conductivity. Morphologies investigation of Co₃O₄/graphene composites indicated that Co₃O₄ nanoparticles with mean diameter of 14nm were uniformly anchored on graphene sheets. The facile one-pot method associated with liquid-phase exfoliated graphene induced Co₃O₄/graphene composite with enhanced specific capacitance of 392 F$\cdot$g${}^{-1}$ at a current density of 1 A$\cdot$g${}^{-1}$. The Co₃O₄/graphene composite also expressed relatively small internal resistance and diffusion resistance (0.36$\mathrm{\Omega }$ and 0.45$\mathrm{\Omega }$, respectively). Moreover, the synthesized Co₃O₄/graphene composite yielded excellent rate performances with only 9.5% capacitance loss when current density was increased by a factor of 10.