Good Electrode Material Research Articles

Effect of Nitrogen and Phosphorous Based Additives on Electrochemical Synthesis of Modified Graphene for Supercapacitor Application

Graphene is a good electrode material for electrochemical energy devices due to its excellent properties such as high electrical conductivity, thermal conductivity, surface area, and chemical and mechanical stability. There are numerous ways to synthesize graphene. Most of these methods are sophisticated, time consuming, expensive, and require hazardous chemicals. Electrochemical exfoliation of graphite is a less complex, quick, affordable, and a greener way to synthesize graphene. Nevertheless, it suffers from restacking of graphene sheets compromising the inherent properties. One of the approaches to overcome restacking is to modify the graphene structure through etching and/or functionalization. In this study an electrochemical synthesis method is proposed in the presence of nitrogen and phosphorous based additives to synthesize porous/functionalized graphene. The synthesized materials’ electrochemical performance were evaluated for supercapacitor applications. Supercapacitors are advantageous over batteries for their superior power density. Improving energy density of supercapacitors remains a challenge. The modified graphene (MG) synthesized via this proposed method is anticipated to improve the electrochemical performance of supercapacitors due to improved porosity/functionalization and controlled restacking. MG was synthesized in the presence of iminoacetic acid (IAA – N1), ethylene disuccinic acid (EDDS – N2), phytic acid (PA – P1), and etidronic acid (EA – P2) via electrochemical exfoliation of graphite. Graphene was synthesized under same conditions in the absence of any additives for comparison. Synthesized material was characterized structurally and electrochemically. UV-visible data confirmed the synthesis of graphene due to the presence of absorbance peak around 270 nm for all samples. Raman spectroscopy was carried out to analyse the ID/IG and I2D/IG ratios. The ID/IG ratios are 1.14 and 0.67 for MG-N1 and MG-P1 respectively compared to 0.21 of graphene. The data confirms few layer graphene is formed with high porosity in the presence of N additive and with low porosity in the presence of P additive. The low I2D/IG ratios 0.1 and 0.18 for N1 and P1 also confirm the synthesis of few layer porous graphene. The cyclic voltammetry data illustrated the double-layer capacitive behavior of MG by having the rectangular shapes within the respective potential windows even at higher scan rates such as 100mV/s. The specific capacitances of MG-N1, MG-N2, MG-P1, and MG-P2 demonstrated an enhancement of 59.1%, 35.6%, 41.6%, and 28.9% respectively at scan rate 5 mV/s compared to the graphene sample. Also, MG showed higher operating potential window compared to graphene. In addition, electrochemical impedance spectroscopy and galvanostatic charge discharge demonstrated the enhanced electrochemical performance for MG. In general, MG synthesized in the presence of N-based less sterically hindered molecule (MG-N1), demonstrates the highest performance among all additive materials. The higher electronegativity of nitrogen facilitates etching over functionalization and MG-N1 showed high porosity according to Raman data. N1 is also less sterically hindered and easily intercalated in graphite structure and contributed for porous graphene formation. The P-based additives, with less electronegativity of phosphorous, could participated in both functionalization and etching. According to Raman data also MG-P1 shows less porosity. These characterization results validate the successful synthesis of MG via etching and functionalization with enhanced electrochemical performances in the presence of additives while electrochemical exfoliation of graphite.

A novel approach to enhancing performance and endurance in GeS2 OTS devices using amorphous carbon doped W2N electrodes

Three–dimensional (3D) cross-point (X–point) memory has gathered interest for its fast data processing and high density, achieved by stacking memory with a selector device to prevent misinterpretation. Ovonic threshold switching (OTS) is a promising selector due to its reversible switching behavior. Although, OTS devices typically employ transition metal nitrides (TMN) such as TiNx, TaNx, and WNx for electrodes owing to their good stability, high melting points, and low resistivity, TMNs can diffuse and degrade device performance by recrystallizing with chalcogenide alloys. Amorphous carbon (a–C) can be a good alternative electrode material due to its low roughness, cost–effectiveness, high work function (WF), and excellent thermal stability. However, the high resistivity of a–C (∼ 150 mΩ–cm) increases threshold voltage (Vth), causing high power consumption. Therefore, combining both a–C and TMN materials can effectively obtain their advantages. This study explores the effect of varying a–C content in W2N electrodes on GeS2–based OTS selectors. The (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes were deposited using DC magnetron co–sputtering. The phase of (W2N)1-xCx (0 ≤ x ≤ 0.25) films transformed from polycrystalline to amorphous with increasing x. Devices with (W2N)1-xCx/GeS2/W2N structure showed decreased Vth and off current, improving from 4.8 to 3.8 V and 8.0–4.17 nA, respectively. The subthreshold slope, distance between traps, and interface trap density (Nit) were extracted using the Pool–Frenkel model. The reduced Vth may be attributed to a higher WF and lower Nit with increasing x. The device’s lifetime improved up to 1.0 × 109 pulses for the highest a–C content in (W2N)1-xCx (0 ≤ x ≤ 0.25) electrodes.

Study of dielectric measurements of Bi4Ti3O12/polystyrene composites as electrode materials for supercapacitors

Eco-friendly, nontoxic and high-energy storage materials are very important for flexible electrode materials. Bi4Ti3[Formula: see text] lead-free, perovskite phase may prove suitable as filler in composites for electrode materials because of its large spontaneous polarization. We have synthesized Bi4Ti3[Formula: see text]/polystyrene (BTO/PS) composites and carried out their structural, morphological and bonding studies with the help of X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), in that order. Dielectric measurements in the broad frequency range of synthesized composites determined by Impedance analyzer. We observed that the dielectric constant of composites increased with filler concentration and decreased with applied field frequency. Bi4Ti3[Formula: see text]/PS composites can be good electrode materials.

Flexible Asymmetric Supercapacitors Constructed by Reduced Graphene Oxide/MoO3 and MnO2 Electrochemically Deposited on Carbon Cloth.

A flexible asymmetric supercapacitor (ASC) is successfully developed by using the composite of MoO3 and graphene oxide (GO) electrochemically deposited on carbon cloth (CC) (MoO3/rGO/CC) as the cathode, the MnO2 deposited on CC (MnO2/CC) as the anode, and Na2SO4/polyvinyl alcohol (PVA) as the gel electrolyte. The results show that the introduction of the GO layer can remarkably increase the specific capacitance of MoO3 from 282.7 F g-1 to 341.0 F g-1. Furthermore, the combination of such good electrode materials and a neutral gel electrolyte renders the fabrication of high-performance ASC with a large operating potential difference of 1.6 V in a 0.5 mol L-1 Na2SO4 solution of water. Furthermore, the ASCs exhibit excellent cycle ability and the capacitance can maintain 87% of its initial value after 6000 cycles. The fact that a light-emitting diode can be lit up by the ASCs indicates the device's potential applications as an energy storage device. The encouraging results demonstrate a promising application of the composite of MoO3 and GO in energy storage devices.

Supercapacitor properties of Ni2+ incrementally substituted with Co2+ in cubic spinel NixCo1-xFe2O4 nanoparticles by sol-gel auto combustion method

The nanoparticle powder of Ni1-xCoxFe2O4 (x = 0.00, 0.25, 0.50, 0.75, 1.00) spinel ferrite was successfully prepared by the sol-gel auto-combustion method. The synthesized nanomaterials were used to prepare spinel ferrite supercapacitor electrode material. The structured phase of prepared nanoparticle powders was studied using XRD which shows the prepared sample consists of nanocrystalline single phase, with cubic spinel ferrite. Furthermore, using FESEM surface morphology of prepared samples was investigated. Ni1-xCoxFe2O4 nanoparticles spinel ferrite structure was verified by FT-IR, which detected distinctive vibrational bands at octahedral and tetrahedral locations.The spinel ferrite type materials are good active electrode materials. In this study, the prepared Ni1-xCoxFe2O4 electrode material is used as cathode material for supercapacitor. The electrochemical behavior of prepared samples was studied and compared by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. An electrochemical measurement study of prepared samples shows excellent performance and desirable cycling stability for supercapacitors. The prepared Ni0.5Co0.5Fe2O4 spinel ferrite gives the highest specific capacitance of 1282 F/g at a current density of 5 mA/cm2 with corresponding energy density of 30 Wh/kg and power density of 301 W/kg. Also, they exhibited outstanding cycling stability for 5000 cycles with 91.24 % capacity retention.

Expeditious and single step synthesis of ceria quantum dots by microplasma discharge method for supercapacitor applications

In the present study, CeO2 quantum dots (QDs) were synthesized by microplasma discharge method out of cerium nitrate precursor suspension using argon gas as plasma medium. The highly energetic electrons in the microplasma plume generate highly reactive metastable OH radicals, which further combine with electrons to form OH− and react with the cerium ions (III) in the precursor solution to form CeO2 QDs. The radical produced during the process was recorded using optical emission spectroscopy. The structural features, oxidation states, morphology, elemental composition and surface area of the synthesized QDs were identified by XRD, Raman, XPS, FE-SEM, HR-TEM, EDS, PL and BET analysis, respectively. The results obtained revealed the formation of cubic phase CeO2 QDs, which was confirmed by XRD and Raman analysis. Agglomerated ceria QDs of spherical shape with an average size of around 5 nm were analyzed from FE-SEM and HR-TEM observations. The electrochemical performance of CeO2 QDs as electrode material was investigated through cyclic voltammetry analysis by an electrochemical workstation. The material achieved a highest specific capacitance of 388 Fg-1 at 1 Ag-1 current density. The commendable electrochemical performance of microplasma synthesized CeO2 QDs was attributed to the minuscule size, high surface area and the presence of Ce3+ ions. This study highlights the synthesis of CeO2 QDs through a single, rapid and amicable process without the use of secondary treatments and suggests the use of CeO2 as a good electrode material for electrochemical applications.

Binder-free cobalt-doped Cu7S4 nanorods as electrode for hybrid supercapacitor with high power density and stable cyclability

Copper-based transition metal sulfides are regarded as good supercapacitor electrode materials due to their cost-effectiveness and considerable theoretical capacity. However, their cycle stability, energy density and rate performance need to be improved. Herein, cobalt-doped Cu7S4 (Co-Cu7S4) nanorods are synthesized at room temperature using environment-friendly routes of co-precipitation and self-sacrifice template processes. Results obtained from electrochemical characterizations and density functional theory calculations can prove the excellent doping kinetics and ideal electrochemical behavior of cobalt ions. Impressively, a high specific capacity of 1302.0 C g−1 (2367.3 F g-1) at 4 A g−1 and rate capabilities of 90.0 % at 10 A g−1 and 61.8 % at 40 A g−1 are obtained. The assembled hybrid supercapacitor (Co-Cu7S4//Active carbon) exhibited superior cycle stability with no insignificant decay after 40,000 charge/discharge process at 5 A g−1 and 20 A g−1, and a maximum power density of 20.4 kW kg−1 at 17.6 Wh kg−1. These excellent electrochemical properties can be ascribed to the porous nanostructures formed by shrinkage during the sulfide process, the rapid electrochemical kinetics, as well as the synergistic effect due to the cobalt ions. This study can provide useful insight into the design and development of electrode materials for high-performance energy storage devices.

Application of molybdenum disulfide material in lithium-ion batteries

In recent years, electric vehicles have been developing rapidly, the most important of which is the development of batteries. Electric vehicles have an increasing demand for lithium-ion batteries with high energy density and long cycle life. Due to the shortage of energy, researchers have conducted extensive research on battery materials and discovered the superiority of molybdenum disulfide as an anode material for lithium-ion batteries. Molybdenum disulfide has good physical and chemical properties. Its good conductivity, high specific capacity, and excellent cycle stability can make it a good electrode material. In this article, we studied in detail different synthesis methods of molybdenum disulfide, such as mechanical exfoliation, hydrothermal, and microwave methods. In addition, its various applications as anodes for lithium-ion batteries are also summarized, such as composite materials of molybdenum disulfide and carbon, composite materials of molybdenum disulfide and transition metal oxides, etc. Finally, this paper summarizes the research on molybdenum disulfide and introduces its shortcomings and future research and development directions.

Aloe vera extract-assisted sol-gel synthesis of NiOx nanopyramids for supercapacitor application

Green synthesis of metal oxide nanoparticles is a cost-effective and sustainable approach that allows tailoring of the size and shape of the nanostructures for versatile applications. In this study, aloe vera extract-assisted sol-gel synthesis of nickel oxide nanoparticles (NiOx NPs) was explored for supercapacitor application. The NiOx NPs were synthesized at different aloe vera concentrations (2.5 and 5 wt%) and calcination temperatures (300, 400 and 500 °C). The phytochemical-assisted synthesis yielded NiOx nanopyramids with pores on their surface which widens as calcination temperature increases. As confirmed by XRD analysis, NiOx crystallite size also increased at higher calcination temperatures. Upon electrochemical characterization, NiOx-400B which was synthesized with 5 wt% aloe vera extract at 400 °C recorded the highest specific capacitance of 721 F g−1 at 1 A g-1 current density with the energy and power density of 10.38 Whkg−1 and 241.08 W kg-1 respectively. The charge storage mechanisms in the samples were gauged using Dunn's method which revealed that NiOx synthesized at higher calcination temperatures exhibited a greater contribution of the diffusion-controlled process. The optimized composition, NiOx-400B, also demonstrated excellent cycle stability by retaining up to 90.4 % of its original capacitance over 1500 cycles. This work is an attempt to investigate the viability of green synthesized nanoparticles in energy storage applications and the novel NiOx nanopyramid substantiates its prospect as a good electrode material for supercapacitors.

One pot synthesis of polyoxometalate@polyaniline/MXene/CNTs quaternary composites with a 3D structure as efficient electrode materials for Li-ion batteries applications

Double transition metal carbides (MXenes) are considered promising candidates for a good electrode material because of their enormous specific surface area, metallic conductivity and hydrophilicity. However, their low capacity, easy oxidation and self-restacking restrict their large-scale application. In this paper, we selected Mo2TiC2Tx MXene as the conductive carrier of polyoxometalate (POM), carbon nanotubes (CNTs) as the linker to construct a novel POM@polyaniline (PANI)/Mo2TiC2Tx/CNTs quaternary composites (denoted as PPMC) with a unique 3D structure by using a facile one pot synthesis strategy. The PPMC with unique 3D structure as an anode material for LIBs exhibits superior lithium storage capacity (621 mAh g−1 at 0.1 A g−1) and promising cyclic stability (445 mAh g−1 after 1000 periods at 1.0 A g−1) and good rate capability. The enhanced performance is mainly attributed to the synergistic effect between components. Our work provides an effective strategy to improve the reversibility and cycling stability of electrode materials for LIBs, which will contribute some reference value to the development of high-performance MXene based electrode materials.

Elektrohemijske karakteristike kompozita V2O5/rGO kao elektrodnog materijala za Mg-jonske baterije sa vodenim elektrolitom

Herein, the composite of vanadium pentoxide and graphene oxide (V2O5/GO) was synthesized by the solgel method. The synthesized composite V2O5/GO was characterized by X-Ray diffraction analysis and Raman spectroscopy. After in situ reduction of GO, the electrochemical characteristics of V2O5/rGO were analyzed by cyclic voltammetry in Mg(NO3)2 aqueous solutions. The V2O5/rGO composite showed following intercalation capacities: initially 139.1 mA h g-1 and 101.8 mA h g-1 after the 10th cycle, which along with easy, fast and low-cost synthesis, make this composite a potentially good electrode material for application in secondary aqueous magnesium-ion batteries.

Supercapacitive behavior and energy storage properties of molybdenum carbide ceramics synthesized via ball milling technique

Energy production and energy storage materials are highly in demand due to their versatility, stability, sustainability, and better conductivity. Low-cost and highly efficient electrode materials (cathode/anode) for electrochemical supercapacitors (SCs) have been highly explored in the last two decades. Herein, we have synthesized Mo2C via a facile, cost-efficient, and green approach (ball milling). This work provides a new route to synthesize Mo2C, as compared with traditional techniques, to reduce the emission of poisonous gases at high temperatures. Furthermore, a comparison of the electrochemical performance of the bulk and nanostructured Mo2C was also investigated. The obtained results proved that smaller particle sizes and higher surface area are the efficient edges for the competitive performance of nanostructured Mo2C. Electron impedance spectroscopy (EIS), galvanostatic charge/discharge (GCD), and cyclic voltammetry (CV) were used to assess the electrochemical performance of bulk and nanostructured Mo2C. Nanostructured Mo2C has delivered 206 F/g at a current density of 0.1 A/g in 3M-KOH electrolyte. Nanostructured Mo2C has shown ultra-long cyclic stability after 20000th GCD cycles with 92 % retention with 100 % Coulombic efficiency. These results predicted that nanostructured Mo2C is a good electrode material for supercapacitors.

Nanostructured Mn-doped V2O5 /carbon belts aggregation spheres composite synthesized via hydrothermal method for supercapacitors

The low conductivity of V2O5 limits its application as an electrode material for supercapacitors. In this study, Mn-doped V2O5/carbon aggregation spheres composite (MnVO/C) was synthesized via a one-step hydrothermal method by introducing Mn2+ and C6H12O6. The structure and morphologies were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical performance results demonstrated that MnVO/C electrode could achieve higher specific capacitance of 232.5F g−1 compare to that of MnVO (125 F g−1). Furthermore, the assembled MnVO/C//MnVO/C device displayed an energy density of 22.47 Wh kg−1, surpassing that of the MnVO/C//YP50 device (8.99 Wh kg−1), thus suggesting its potential as a good candidate electrode material for supercapacitors.

Surface‐Modified ZnCo2O4 Nanoparticles as Binder‐Free Electrode for All Solid‐State Asymmetric Supercapacitor

AbstractChoice of electrode material is crucial to the development of high‐performance supercapacitors. Since surface properties are key to the performance of an electrode material for supercapacitors, surface chemical treatment of electrode materials is an interesting topic of research. ZnCo2O4 (ZCO) is a low‐cost binary transition metal oxide with high theoretical conductivity and charge storage capacity making it a good choice for supercapacitor electrode. Herein, we present a systematic investigation of the influence of four different surface modifier (3 surfactants, 1 mineralizer) on ZCO electrode directly grown on Ni foam to compare the relative influence on the performance of the modified ZCO electrode. Analyses of the modified ZCO electrodes revealed the formation of cubic spinel phase of ZCO with average particle size of ~30 nm. The sodium dodecyl sulfate (ZCO−S) modified electrode (ZCO−S) exhibited the best electrochemical performance with specific capacitance of 1988 F/g at 1 A/g and 87 % capacity retention after 7000 cycles at 10 A/g. Further, an all‐solid‐state asymmetric supercapacitor (ASC) was fabricated with ZCO−S on Ni foam and carbon nanotube combination which exhibited specific capacitance of 102 F/g at 1 A/g corresponding to power density of ~1599 W‐kg−1 establishing ZCO−S as a very good electrode material for supercapacitor.

Facile sonochemical synthesis of nanostructured FeWO4-rGO and CuCo2O4 nanocomposite for high-rate capability and stable asymmetric (CuCo2O4//FeWO4-rGO) supercapacitors

The present work reports iron tungstate (FeWO4) nanostructures with reduced graphene oxide (rGO) as a novel anode material for enhancing the electrochemical properties of asymmetric supercapacitors. The FeWO4-rGO composite nanostructures were successfully synthesized by the one-pot sonochemical method. The synthesized nanocomposites crystal structure and phase purity were investigated using the powder X-ray diffraction (XRD) technique. The Fourier transform infrared (FT-IR) spectrograms demonstrate the presence of functional groups in the composite. The composite's morphology was examined using the high-resolution transmission electron microscopy (HR-TEM) and the field emission scanning electron microscopy (FE-SEM), and it was observed that the FeWO4 nanostructures were uniformly distributed on the reduced graphene oxide surface. The cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) analyses were used to evaluate the electrochemical performance. After 5000 cycles at 10 mA cm− 2, the FeWO4-rGO composite achieved a better rate of efficiency and outstanding cycling performance, with capacitance retained at 68% and 77.8%, respectively. In 1 M Na2SO4, an asymmetric device (CuCo2O4//FeWO4-rGO composite) achieved a high energy density of 21.5 W.h Kg−1 and a power density of 147 W Kg−1. In the FeWO4-rGO nanocomposite, the reduced graphene oxide could enhance the conductivity and the free diffusion processes for the quick ion transport and easy ion access to the storage sites. The obtained results indicated that the FeWO4-rGO nanocomposite could be a good anode electrode material for the next-generation energy storage applications.

Surface modification of metal phosphate Binder-Free electrode with metal hydroxides for supercapattery

Supercapattery is one of the emerging alternative energy storage technologies and numerous recent studies have been done in search of good electrode material for its application. Cobalt phosphate (Co3(PO4)2) is a promising candidate due to its abundance, low cost, valence states variation, and good faradaic property. However, cobalt phosphates have limited surface area, affecting its electrochemical performance. To overcome that, herein Co3(PO4)2 was synthesized via sonochemical method and calcined at various temperatures to obtain the best calcination temperature followed by coating of cobalt hydroxide (Co(OH)2) layer. The synthesis of Co3(PO4)2 and coating of Co(OH)2 over cobalt phosphate was observed through X-ray diffraction analysis (XRD) and the morphology of the synthesized nanostructures was observed using Field emission scanning electron microscopy (FESEM). Cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy analyses were carried out. The results showed calcination temperature of 200 °C followed by coating of Co(OH)2 using 2 mM metal precursor as the optimized sample. This sample exhibited the fascinating electrochemical performance of specific capacitance (2111.83F g−1 at 1 A g−1), energy density (72.51 Wh kg−1 at 1 A g−1), and power density (2357 W kg−1 at 10 A g−1) and fabricated supercapattery demonstrated outstanding cyclic stability up to 84 % over 15,000 charge/discharge cycles.

An Ultrastable Tetrabenzonaphthalene-Linked conjugated microporous polymer functioning as a high-performance electrode for supercapacitors

BackgroundConjugated microporous polymers (CMPs) have been applied widely in several energy storage applications. Triphenylamine derivatives are good electrode materials that can be processed into SC devices because of their high charge mobilities, unique electronic properties, and high redox activity. MethodsWe prepared two novel tetrabenzonaphthalene-linked conjugated microporous polymers (TBN-pH CMPs) through [4 + 2] and [4 + 3] Schiff-base condensations of 2,7,10,15-tetra(4-formylphenyl)tetrabenzonaphthalene (TBN-PhCHO) with tetrakis(4-aminophenyl)ethene (TPE-4NH2) and tris(4-aminophenyl)amine (TPA-3NH2), respectively. Fourier transform infrared, and solid-state 13C NMR spectroscopy investigated the structures of the as-prepared CMPs. Significant FindingsThese CMPs, had large surface areas and outstanding thermal stability at temperatures of up to 400 °C, making them suitable for use as electrodes in supercapacitor (SC) systems. Indeed, the TBN-TPA CMP–based electrode had high specific capacitances (251 F g− 1 measured at 0.5 A g–1) and capacity retentions (94%, measured after 5000 cycles at 10 A g–1) when tested in three-electrode systems. We attribute the remarkable electrochemical activity and conductivity of the TBN-TPA CMP electrode to its large specific surface area (230 m2 g–1) and chemical structure featuring stacking of the benzene rings of its redox-active triphenylamine moieties.

Preparation of high performance supercapacitors with nitrogen and oxygen self-doped porous carbon derived from wintersweet-fruit-shell

In this work, seedless wintersweet-fruit-shell was selected as carbon precursors, carbonized and labeled as WFC. WFC was activated by different proportions of KOH, the product was denoted as WFC-X (X = 1, 2, 3, 4 stand for the mass ratio between KOH and WFC). The morphology and structure of WFC and WFC-X were characterized by SEM and TEM. The crystallization of different materials were characterized by XRD and Raman.The electrochemical properties of WFC and WFC-X were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Among these materials, WFC-2 has the best electrochemical performance. It has the largest specific surface area (1489.31 m2 g−1). The specific capacitance of WFC-2 can achieve 433 F g−1, it has a capacitance retention rate of 95.20% after 5000 charge and discharge cycles. In order to more comprehensively test the electrochemical performance of WFC-2, a symmetrical supercapacitor was assembled using WFC-2. The assembled WFC-2//WFC-2 symmetric supercapacitor has been tested in 6 M KOH and 1 M Na2SO4 as the electrolyte. When the power density is 350 W kg−1, the energy density can get 14.07 Wh Kg−1 in 6 M KOH electrolyte. The symmetric supercapacitor has a capacitance retention rate of 92.36% and a coulomb efficiency of 96.55% after 5000 charges and discharges. At 1 M Na2SO4 electrolyte, when the power density is 500 W kg−1, the energy density can reach 8.33 Wh Kg−1. The symmetric supercapacitor has a capacitance retention rate of 92.44% and a coulomb efficiency of 98.11% after 5000 charge and discharge cycles. WFC-2 may be a good electrode material for supercapacitor due to its excellent electrochemical properties.

N-, P-, and Ni-Co-doped Porous Carbon from Poplar Powder and Graphene Oxide Composites as Electrode Materials for Supercapacitors

Poplar powder was used as a raw material to prepare an electrode material in supercapacitors by doping modification, carbonization, and activation. The lignin-removed poplar powder was mixed with graphene oxide, melamine, and diammonium hydrogen phosphate and then compounded with nickel sulfate. Upon carbonization and activation with KOH, the composite becomes a hierarchical porous carbon material with a pore volume of 0.93 cm3 g–1 and a surface area of 1214.1 m2 g–1. At 0.5 A g–1 current per square meter, the specific capacitance was 407.5 F g–1. In addition, 92.6% of the capacitance remained even after 3000 charging and discharging cycles. There was an outstanding power and energy density of 12.32 W h kg–1 at 499.99 W kg–1 for a symmetric supercapacitor in 6 M KOH. Co-doped porous carbon with nitrogen, phosphorous, and nickel could be a good electrode material for energy storage devices.

Self-Assembled Hierarchical Silkworm-Type Bimetallic Sulfide (NiMo3S4) Nanostructures Developed on S-g-C3N4 Sheets: Promising Electrode Material for Supercapacitors

An electrode material composed of bimetallic sulfides on g-C3N4 typically enhances the energy storage capacity of devices due to the merits of each component, but it still suffers from low energy density over long cycles. Although Ni-based bimetallic sulfides have become good electrode materials for supercapacitors, practical applications of these materials are hindered due to unsatisfactory cycling stability. Here, we demonstrate a simple two-step in situ approach to prepare bimetallic sulfide nanobulbs on a sulfur-doped graphitic carbon nitrate matrix for a NiMo3S4@S-g-C3N4 composite, which is further used for supercapacitor devices. A small amount of sulfur doping to g-C3N4 enhances the conducting channels for electron transportation. An NMS@S-gC nanocomposite clearly shows the formation of small nanobulbs that are formed as silk warm-type hierarchical morphology structures and these were wrapped on the surface of S-gC porous nanosheets. The device made up of these composites exhibited a maximum specific capacitance of 142.4 F g–1, a high energy density of 41.4 Wh kg–1, and a power density of 723.5 W kg–1 at a current density of 1 A g–1. Meanwhile, in a three-electrode device configuration, the working electrode demonstrates a specific capacitance of 934.2 F g–1 at 1 A g–1, which is 1.6 times greater than that of bare NiMo3S4. Moreover, the capacitance retention of the device is about 91% even after 5000 cycles at 8 A g–1. The results obtained in this investigation surpassed most reported metallic sulfides on g-C3N4. Hence, this work could give a different pathway for the synthesis of electrode materials for energy storage devices.