High Specific Capacitance Value Research Articles

Designing a hierarchical structure of nickel-cobalt-sulfide decorated on electrospun N-doped carbon nanofiber as an efficient electrode material for hybrid supercapacitors

The intent of designing and exploring novel active electrode materials is to enhance the electrochemical performance of supercapacitors. Herein, a hierarchical structure of nickel-cobalt-sulfide nanostructures (NiCo2S4) decorated on the electrospun N-doped carbon nanofiber (CNF), NiCo2S4@CNF, is manipulated using a one-step and simple hydrothermal approach. The fabricated hierarchical structure of the NiCo2S4@CNF is featured by a large surface area and a high porosity that serve as ion diffusion channels. Therefore, it manifests high specific capacitance and specific capacity values of 377.2 C g−1 and 754.4 F g−1 at a current density of 1 A g−1, respectively. Furthermore, a NiCo2S4@CNF//CNF hybrid supercapacitor in which a positive electrode of NiCo2S4@CNF is assembled with a negative electrode of CNF to estimate the electrochemical performance of the NiCo2S4@CNF. As a result, the device has a superior energy density of 65.6 and 52.5 Wh kg−1 at a power density of 665 and 1313.8 W kg−1, respectively. Moreover, the device reveals good stability with capacitance retention of 72% after 3000 charge/discharge cycles. These outstanding results enable the designed hierarchical structure of the NiCo2S4@CNF to be a promising electrode material for supercapacitors (SCs) applications.

Diffusion and surface charge studies of waste cow dung derived highly porous carbon as a facile electrode for solid-state supercapacitors

Carbon-based materials generated from biowaste have recently attracted interest due to their exceptional surface and conductive properties. Cow dung derived porous carbon (CDPC) with a 3D structure and linked pores is synthesized in this study, making it an alternative electrode for supercapacitors (SC). Herein, we studied the diffusion and surface charge contribution and their relationship with the scan rate. Diffusion charge contribution is more prevalent at lower scan rates. Furthermore, a large fraction of surface charge contribution of 69.2 % at a high scan rate of 100 mV/s indicates rapid electrochemical kinetics and hence high-rate performance even at higher current densities. In addition, utilizing a 1 M H 2 SO 4 electrolyte, the CDPC electrode has attained a high specific capacitance value of 210 F/g at 0.5 A/g. Furthermore, symmetrical solid-state SC device displayed high energy density of 36 Wh/kg at good power density of 800 W/kg along with remarkable cyclic stability of 92.6 % after 10,000 charge-discharge cycles. Hence, these findings demonstrate that investigating surface and diffusion charge contributions opens up new avenues for tuning the supercapacitor performance. • Waste cow dung derived carbon obtained by hydrothermal carbonization and activation • Surface and diffusion charge contribution studies are performed for CDPC electrode. • Solid-state symmetrical SC assembled using two CDPC electrodes and gel electrolyte • Device retains long cycle life of 92.6 % after 10,000 charge-discharge cycles. • Device delivers high energy density of 40 Wh/kg at a power density of 907 W/kg.

Construction of CoMoO4 nanosheets arrays modified by Ti3C2Tx MXene and their enhanced charge storage performance for hybrid supercapacitor

MXenes are considered to be a new two-dimensional material with excellent conductivity, large specific surface area, and fast transfer channels for electrons, thereby provides efficient bridge to improve conductivity and structural stability of battery-type electrode materials. In this work, Ti3C2Tx MXene is integrated into CoMoO4 nanoarrays by a simple hydrothermal process to form a cross-supported nanoarray structure of CoMoO4-Ti3C2Tx with three-dimensional heterogeneous interface. It is worth noting that CoMoO4 thinner nanosheets expose more electrochemical active sites under synergistic effect of Ti3C2Tx MXene, thereby greatly increases the specific capacity of CoMoO4 nanoarrays. At the same time, it can alleviate the volume expansion and contraction of CoMoO4 materials during the charge-discharge process, and thus improves their cycle life performance. The CoMoO4-Ti3C2Tx nanoarrays show a high specific capacity value of 870.7 C g−1 at a current density of 1 A g−1,and capacity retention rate of 68.2 % after 6000 cycles, which is better than the unmodified CoMoO4 electrode (specific capacity: 737.0 C g−1, retention rate: 54 % after 5000 cycles). Furthermore, a hybrid supercapacitor fabricated by CoMoO4-Ti3C2Tx and N-doped graphene electrode delivers high capacitance value of 148 F g−1 and energy density of 46.3 Wh kg−1. This work demonstrates great potential of the CoMoO4-Ti3C2Tx nanoarrays for high-performance supercapacitors.

Mixed metal sulfides (FeNiS2) nanosheets decorated reduced graphene oxide for efficient electrode materials for supercapacitors

Mixed metal oxides, hydroxides and sulfides have been extensively studied as potential electrocatalyst for oxygen evolution reactions however particularly mixed metal sulfides have not been explored yet as electrode material for supercapacitors. In the present work, mixed metal sulfides (FeNiS2) have been synthesized from a hydroxide precursor. In the second step, these FeNiS2 nanosheets (∼2.5 nm thickness) are decorated on rGO (reduced graphene oxide) surface by in-situ to design the efficient electrode material for supercapacitor applications. A very high value of specific capacitance as 1013 F/g is observed for a current density of 2 A/g, and it is also seen that a significant enhancement of specific capacitance is noticed for rGO/FeNiS2 as compared to the virgin material (FeNiS2). The capacity retention is enhanced from 22% of FeNiS2 to 61% of G_FeNiS2 when current density increases from 2 to 10 A/g, representing its enhanced rate capability. This work highlights the advantages of FeNiS2 decorated on rGO in electrochemical characterizations and contributes to providing suitable electrochemical activities and long-term cyclic stability for practical applications.

Effect of annealing temperature on supercapacitive behaviour of manganese dioxide (MnO2) thin-film prepared by electrodeposition technique and characterization

The purpose of this study is to demonstrate the construction of Manganese Dioxide (MnO2) Thin-Film on a stainless-steel substrate (AISI304) using the electrodeposition process. A thin MnO2 layer Potentiostatically formed by electrodeposition technique from MnSO4.H2O (aqueous manganese sulphate monohydrated) solution was used to investigate the electrodes’ super-capacitive capabilities. The impact of annealing temperature on the electrochemical characteristics of some materials at temperatures ranging from 100°C-500°C was investigated. The surface morphology of annealed material at 100°C, 200°C, 300°C, 400°C, and 500°C was investigated utilizing a SEM (scanning electron microscope). At 200°C, the cyclic Voltammogram is used to investigate the electrochemical characterisation. The highest value of specific capacitance was calculated from this data and was found to be 184.42F g–1 for 10 mV/s. Utilizing galvanostatic discharging and charging techniques, as well as electrochemical impedance spectroscopy, this research investigates the behaviour of super capacitive materials.

Effect of different precursors on the electrochemical behavior of CuS nanostructures as electrode material for supercapacitor applications

In the present work, we synthesized copper sulfide (CuS) nanostructure using the co-precipitation technique by employing two different copper precursors such as copper nitrate, copper chloride with water as a solvent in order to investigate the effect of different precursors on the electrochemical behavior of CuS nanostructures as electrode material for supercapacitor application. X-ray diffraction analysis confirmed the pure phase (hexagonal-P63/mmc) formation of CuS nanostructures. The morphological and elemental compositional studies are done by scanning electron microscopy and energy-dispersive X-ray spectroscopy respectively. Electrochemical characterizations like cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) were utilized to analyze the super capacitive properties of the fabricated electrode material in a three-electrode system using 2 M KOH solution as an aqueous electrolyte. The highest value of specific capacitance is found to be 346.66F/g at 2 A/g for the sample synthesized via copper nitrate precursor. Furthermore, it also displayed good cycling stability with more than 80 % retention of capacitance over 500 GCD cycles. Hence, the analysis of the result revealed that precursors play a major role in modifying the electrochemical properties.

Influence of fuel to oxidizer ratio on the supercapacitive properties of NiO synthesized by solution combustion method

Porous Nickel oxide nanocrystallites were successfully synthesized by a facile single-step glycine assisted solution combustion method without a post calcination treatment. Effect of fuel to oxidizer (F/O) ratio on the combustion behaviour, crystallite size, surface characteristics, morphology, and agglomeration were thoroughly investigated. A systematic variation of crystallite size with F/O ratio was revealed from PXRD studies. BET studies showed a decrease of surface area with increase of F/O ratio. Highly porous morphology of NiO nanocrystallites synthesized at low F/O ratio (0.5) was evident from scanning electron micrograph (SEM). Transmission electron microscopy (TEM) studies showed polycrystalline nature of the material. NiO nanocrystallites exhibit high thermal stability, which was revealed from thermal analysis. The maximum specific capacitance obtained for NiO synthesized at different F/O ratios ranged from 215.6 to 99.2 C/g at 5 mV/s scan rate and 174.7 to 73.0 C/g at 10 A/g current density. Highest value of specific capacitance and lowest values of equivalent series resistance and charge transfer resistance were exhibited by NiO synthesized at low F/O ratio of 0.5. The enhanced electrochemical performance of the sample synthesized at low F/O ratio was benefited mainly from its high surface area and optimal pore size for the diffusion of ions and electrons within the electrode. An asymmetric device fabricated using NiO as the positive electrode and activated carbon derived from phyllanthus emblica as the negative electrode and 3 M KOH as the electrolyte delivered an energy density of 12 Wh/kg at a power density of 427 W/kg.

High Aspect‐ratio Germanium‐Tin Alloy Nanowires: Potential as Highly Efficient Li‐Ion Battery Anodes

AbstractHere, the fabrication of a high aspect ratio (>440) Ge1−xSnx nanowires with super‐thin (≈9 nm) diameter, much below the Bohr radius, using a simple solvothermal‐like growth method under supercritical toluene conditions at a reaction temperature of 440 °C is reported. Ge1−xSnx nanowires are grown with varying amounts of Sn in Ge lattice, between 3.1 to 10.2 at%. The growth of the Ge1−xSnx alloy nanowires is achieved without any additional catalysts, and directly on current collector substrates (titanium) for application as Li‐ion battery anodes. The electrochemical performance of the binder‐free Ge1−xSnx nanowires as an anode material for Li‐ion batteries is investigated via galvanostatic cycling and detailed analysis of differential capacity plots. The dimensions of the nanowires, and the amount of Sn in Ge, are critical to achieving a high specific capacity and capacity retention. Ge1−xSnx nanowires with the highest aspect ratios and with the lowest Sn content (3.1 at%) demonstrate exceptional capacity retention of ≈90% and 86% from the 10th to the 100th and 150th cycles respectively, while maintaining a very high specific capacity value of 1176 and 1127 mAh g−1 after the 100 and 150 cycles respectively.

2,6-diaminoanthraquinone-functionalized S,N-codoped graphitic biomass carbon as advanced electrode materials for supercapacitors

Supercapacitors have rapidly become an important electrochemical energy storage system due to their advantages such as fast power delivery, fast charging, and long cycle life, and play a dominant role in the field of high power transmission or absorption. Among various electrode materials, biomass carbon exhibits exciting electrochemical properties and impressive prospects owing to its wide availability, environmentally friendly renewability, and low-cost electricity storage. In this work, we report sulfur/nitrogen-doped biomass carbon with covalently grafted anthraquinone organic small molecules on its surface, derived from banana leaves (DAAQ-S/N-C-850). The prepared DAAQ-S/N-C-850 electrode material exhibits a high specific capacitance value of 355.3 F g−1 at a current density of 5 mV s−1 in three-electrode system. The experimental results show that the double doping of S and N can effectively improve the electrical conductivity of the electrode material, and the synergy between DAAQ organic molecules and double doping can availably improve the pseudocapacitive performance of the electrode material. Moreover, the asymmetric supercapacitor of DAAQ-S/N-C-850//CNT@RGO achieves energy density (30.9 Wh kg−1) and power density (0.714 kW kg−1) in 1 M H2SO4 electrolyte. This article proposes functionalized S/N-doped biomass carbon and provides a novel method for the application of biomass carbon in the field of energy storage.

Synthesis of Mn2V2O7 nanopebbles via hydrothermal method and its high-efficiency energy storage for supercapacitors

For its improved electrochemical features, such as a longer life cycle, higher specific capacitance, and higher specific power, the supercapacitor has acquired increased attention. Between the battery and the conventional capacitor, the supercapacitor fills the energy and power gaps. The supercapacitor has been suggested as an energy storage device for higher-power uses in the future. MnOOH nanorods and Mn2V2O7 nanopebbles were synthesised through a hydrothermal method, and those materials were studied by X-ray diffraction (XRD), thermal graviometric analysis (TGA), Fourier transformed infrared (FT-IR), Raman spectra, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and transmission electron microscope (TEM). The XRD results revealed the creation of a monoclinic phase of synthesised MnOOH nanorods and Mn2V2O7 nanopebbles. The supercapacitance behaviour of crystalline MnOOH nanorods and Mn2V2O7 nanopebbles was examined using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD) techniques. The Mn2V2O7 nanopebbles achieved a high specific capacitance value of 1310 F/g at 0.25 A/g. The assembled asymmetric supercapacitor of Mn2V2O7@NF//AC@NF has a good capacitance retention value of 98 % and matches a coulombic efficiency of 95.5 % over 5000 cycles. In an alkaline medium, the energy density and power density of Mn2V2O7@NF//AC@NF are 53.9 Wh k/g and 1564 W k/g, respectively.

Novel porous nitrogen-doped carbon composite with CNTs/Cu-Ni as high-performance supercapacitor electrode

• Two-step method was developed to prepare a novel porous carbon material. • Novel porous carbon material was as high-performance supercapacitor electrode. • The supercapacitor possessed outstanding energy and power density. • The carbon material had a high specific capacitance value and cycling stability. The annealing approach is usually used to synthesize carbon-based materials. We use polystyrene (PS) microspheres as a template to composite with carbon nanotubes (CNTs) loaded by Cu-Ni ions. After One-step high-temperature treatment, the PS microspheres disappear, and the composite materials become a three-dimensional porous structure. At the meantime, the Cu-Ni ions are reduced and attached to the material (CNTs/Cu-Ni/CP (CMP)). Then, the CMP material is coated with Polyaniline (PANI). The two-step high-temperature treatment accomplishes the Nitrogen-doped process of the material (CNTs/Cu-Ni/CP@CPANI (CMPN)). Electrochemical analysis indicates that materials have a high specific capacitance value (356F/g at 0.5 A/g). After 10,000 cycles of charging and discharging, the capacitance retention rate is 92.57 %. The assembled symmetrical supercapacitor possesses outstanding energy and power density (11.92 Wh kg −1 at 700.73 W kg −1 ).

Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications

The aim of this study was to synthesize CuFe2O4 together with g-C3N4 and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe2O4 was successfully synthesized together with g-C3N4 and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm2 at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm2 and 300 mW/cm2, respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.

Highly scalable and pH stable 2D Ni-MOF-based composites for high performance supercapacitor

Supercapacitors are projected as one of the most promising candidates for next-generation energy storage devices. Herein, we strategically developed a microporous two-dimensional Ni-metal organic framework (MOF: IITKGP-20A, IITKGP stands for the Indian Institute of Technology Kharagpur) which is highly scalable and thermodynamically stable over a wide pH range (2–10), intended for energy storage applications. Graphene oxide (GO) with different wt% (3, 5, and 7) was introduced with the MOF precursors to form in-situ MOF@GO composites (IITKGP-20A-GO3, IITKGP-20A-GO5, and IITKGP-20A-GO7 respectively), out of which IITKGP-20A-GO3 exhibits significantly high specific capacitance value (∼840 F g−1 at 2 A g−1), which is one of the highest among the bare MOFs and their composites/derived materials. To verify its practical potentiality as positive electrode material, an asymmetric supercapacitor (ASC) device was fabricated displaying the specific capacitance of 111.4 F g−1 at a current density of 2 A g−1 while maintaining a high specific capacity of 65 F g−1 even at a higher current density of 10 A g−1. Moreover, the device produced 30.7 W h kg−1 (0.031 W h cm−3) energy density with a very high power density of 388.5 W kg−1 (0.394 W cm−3) with excellent retention of 84% cycle life up to 7000 cycles.

Synthesis of new mixed metal oxide RuNi2O4 phase decorated on reduced graphene oxide for supercapacitor applications

• New mixed metal RuNi 2 O 4 nano particle decorated rGO (RuNi 2 O 4 /rGO) has been synthesized. • RuNi 2 O 4 /rGO offers high specific capacitance of 792 Fg −1 . • RuNi 2 O 4 /rGO retains 93% of initial specific capacitance after 10,000 cycles. Design and fabrication of high performance energy storage devices using different mixed metal oxides decorated on conducting 2D surfaces are being investigated intensively now a days. In the present work, we have explored to synthesize a new mixed metal oxide (RuNi 2 O 4 ) containing Ru and Ni and decorate the nanoparticles of these mixed metal oxides on highly conducting 2D reduced graphene oxide (rGO) surfaces to prepare efficient electrodes for high performance supercapacitors. The microstructure and compositional analyses of the composite structure are carried out by powder X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The XRD data have been analysed by Rietveld refinement. The electrochemical performance of the device has been investigated via galvanostatic charging-discharging (GCD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. It is seen that RuNi 2 O 4 /rGO composite shows a very high specific capacitance of 792 Fg −1 compared to the values of rGO and pristine RuNi 2 O 4 as 235 and 367 Fg −1 , respectively. Due to the combined effect of the electric double layer contribution of rGO and the faradaic contribution of RuNi 2 O 4 , RuNi 2 O 4 /rGO composite results in this high value of specific capacitance in the composite structure.

Cost effective, metal free reduced graphene oxide sheet for high performance electrochemical capacitor application

A simple, cost-effective, and large-scale production of metal-free self-assembled graphene oxide sheets (GOS) with an area of 15 × 15 cm is synthesized using a modified Hummer's method. The reduced graphene oxide sheet (rGOS) was prepared by heat-treating GOS at a range of 300 °C in a hydrogen atmosphere. The XRD results show that GOS has an interlayer distance of 0.79 nm and the rGOS has an interlayer distance of 0.34 nm. The electrochemical analysis of rGOS and GOS was investigated. The porous structure, large-size sheet, and fast transit kinetics of electrochemical analysis and electrons on the interface of electrolyte/electrode contributed to the rGOS showing the high performance of an electrochemical capacitor. The GOS has a specific capacitance value of 54 F/g at 1 A/g, while the reduced GOS has a higher specific capacitance value (469 F/g at 1 A/g), which is 8.6-fold higher than the GOS and has excellent cycle stability. Heat-treated rGOS is regarded as a strong, cost-effective, and scalable electrochemical capacitor material.

Impact of Nitrogen Functionalities in a Mesoporous Carbon to Use It As a Conductive Material in Cathodes for Li-S Batteries

The Li-S batteries have gradually become a good candidate for energy storage due to its high specific theoretical capacity value (1675 mA h g-1), with an order of magnitude ten times higher than that of ordinary Li-ion batteries. The performance of these devices significantly depends on the physicochemical properties of the materials that compose them. Therefore, it is necessary to obtain cathodes that help to minimize the well-known shuttle effect causing a drastic decrease in the capacity of the batteries due to the formation of insoluble lithium sulfide species. The carbonaceous materials obtained from templates offer the advantage of modulating and incorporating nitrogen to retain lithium sulfides physically and chemically and, in this way, keep a high specific capacity through a large number of cycles. To understand the deactivation process of these batteries, three N-doped carbons were synthesized varying the carbonization temperature (600- 850 °C) to obtain different N-functionalities and thus evaluate their effect on the electrochemical performance of these batteries.A N-doped mesoporous carbon was synthesized using SBA-15 as a template, as nitrogen and carbon sources, ethylenediamine (EDA), and carbon tetrachloride were used (CCl4). The silica was impregnated with them followed by carbonization variating the temperature (600-850 °C) to incorporate different nitrogen functionalities, the obtained material was labeled as MC-x, with x = carbonization temperature. The S/C composite were formed with the melt-diffusion process at 155 °C for 6 h with 10 wt.% of S8. Raman spectroscopy was used to study the graphitization changes, XPS was used to determine the functional groups present in the materials, and the efficiency in sulfur inclusion within the MC-x pores was studied by XRD, TGA, and Ads-Des isotherms, while by SEM-EDX the S8 distribution on the material was evaluated. The electrochemical evaluation was carried out with the use of discharge tests at 0.1 C and electrochemical impedance spectroscopy (EIS). For the battery assembly, lithium was used as anode and the cathode was formed with the composite, PVDF, and acetylene black in a ratio of 70:15:15 dispersed in N-methyl pyrrolidone. The electrolyte was a 1 M solution of the LiTFSI salt with 0.1 M LiNO3 dissolved in DOL and DME (v/v,1:1).The nitrogen content decreased with the increase in the carbonization temperature, the XPS analysis revealed that the pyridinic and pyrrolic functionalities decreased at higher temperatures, while the graphitic nitrogen content increase. This result is correlated with that obtained from Raman where the carbonized material at 850°C presents greater graphitization that involves better electronic conductivity. The XPS result for the S/C composites indicates the formation of S-C bonds that helps to stabilize the active material during the redox reactions, however, for MC-600 and MC-700 the XPS show the presence of sulfated sulfur forms that were not detected for MC-850 affecting the electrochemical behavior of these batteries. The EIS results showed a decrease in the resistance to charge transfer when the MC-850 material was used (43 Ω) compared to the one with the lowest carbonization temperature, i.e MC-600 (105 Ω). The battery with MC-850 presented a higher initial discharge (983 mAhg-1), while the lowest value was obtained with MC-600 (520 mA h g-1). After 100 cycles, the same trend was maintained with a final value of 420 mA h g-1 for MC-850. This result is interpreted because of the decrease in the degree of graphitization of the carbonaceous material that leads to a decrease in electronic conductivity. The previous results corroborate the importance of controlling the nitrogen functionalities and content during the synthesis of the carbonaceous material to improve the electrochemical performance.The authors wish to thank Universidad de Antioquia UdeA and the Microscopy Laboratory at Instituto Tecnológico Metropolitano (ITM) for their support. Figure 1

Binder free electrodeposition fabrication of NiCo2O4 electrode with improved electrochemical behavior for supercapacitor application

The supercapacitor is a ground-breaking energy storage device that has exploded in popularity in recent decades. The present study demonstrated a binder-free electrodeposition technique to produce NiCo2O4 for two different deposition times, namely 6 min (NC6) and 10 min (NC10). The cubic phase and purity of manufactured samples were validated by X-ray diffraction (XRD) patterns. Scanning Electron Microscopy (SEM) analysis revealed a flower-like arrangement in the NC6 sample and a sea-coral morphology in the NC10 sample. The electrochemical characteristics of NC6 and NC10 samples are tested using three- and two-electrode systems. The results showed that the NC6 sample had an extremely high specific capacitance value of 1472 F/g at 1.0 mV/s scan rate. The galvanostatic charge-discharge (GCD) study demonstrates that NC6 and NC10 have a rate-performance of 88.47 and 90.81% at a higher current density of 10.0 A/g, respectively. Outstanding cycle stability with 129% retention is observed for the two-electrode setup, which was 83% for NC6 and 81% for NC10 in the three-electrode system. The simple manufacturing method and outstanding performance of NiCo2O4 electrodes open-up new opportunities in the field of energy.

Synthesis and Characterization of Activated Carbon Derived from Rubberwood Sawdust via Carbonization and Chemical Activation as Electrode Material for Supercapacitor

This research aims to study the physical and electrochemical properties of the activated carbon derived from rubberwood sawdust as electrode material for supercapacitors. Rubberwood sawdust, waste from the wood processing industry, was used as the precursor for synthesizing activated carbon using potassium hydroxide (KOH) as an activation agent. The carbonization was carried out at 400 °C under the nitrogen atmosphere. In this experiment, the rubberwood sawdust chars were activated by impregnating KOH solution using the impregnation ratios 1:1 and 1:3 (Char: KOH). After that, the samples were activated at 700, 800, and 900 °C, respectively. The adsorption isotherm, surface area, total pore volume, pore size distribution, and structure porosity were investigated. The XRD was used to examine the structural characteristics. The morphology of the sample was characterized by FESEM. The surface functional group of the samples was determined by FTIR and Raman spectroscopy. The three-electrode testing consists of the activated carbon samples coated on aluminum foil (Working electrode), Ag/AgCl (Reference electrode), and platinum wire (counter electrode) in 1 molar of KOH. According to the research, the activated carbon at an impregnation ratio of 1:3 with an activation temperature of 900 °C presented the highest surface area, total pore volume, and average pore diameter as 1,574.39 m2/g, 0.6906 cm3/g, and 1.89 nm, respectively. The cyclic voltammetry (CV) result showed a high specific capacitance value of 54.08 F/g at a scan rate of 5 mV/s in the case of the impregnation ratio of 1:3 with an activation temperature of 900 °C. Thus, the activated carbon derived from rubberwood sawdust waste as an electrode material can be a promising candidate for supercapacitors due to its outstanding electrochemical properties.

Facile synthesis of novel PANI covered Y2O3–ZnO nanocomposite: A promising electrode material for supercapacitor

In the present study, pristine ZnO, Y2O3, binary PANI-Y2O3, PANI-ZnO, Y2O3–ZnO, and novel ternary PANI-Y2O3–ZnO nanocomposites were prepared via co-precipitation and ultra-sonication techniques. The XRD pattern evident the formation of pristine oxides and binary/ternary nanocomposites. FTIR analysis showed the benzenoid ring stretching, C–H, and C–N in-plane/out-of-plane vibrations due to PANI and metal-oxygen bonds vibrations, which confirmed nanocomposite formation with PANI. FE-SEM images revealed that PANI covered on Y2O3–ZnO nanocomposite and EDX exhibited the existence of zinc and yttrium in synthesized products. The DC conductivity of ternary nanocomposites is higher than others. The Cyclic Voltammetry (CV) exhibited that PANI-Y2O3–ZnO nanocomposite has greater specific capacitance (Csp) 412 Fg-1 at the scan rate of 10 mVs−1. The Galvanostatic Charge-Discharge (GCD) also evident the maximum specific capacitance 873 Fg-1 of ternary nanocomposite at an applied current density of 3 A/g with increased energy density 73 Wh/kg and power density 9.1 kW/kg. Electrochemical Impedance Spectroscopy (EIS) showed that PANI-Y2O3–ZnO nanocomposite has the lowest value of polarization (Rp) resistance and solution (Rs) resistance. The highest value of specific capacitance of novel ternary nanocomposite is due to the rapid charge transfer rate and the enhanced surface-dependent electrochemical properties by PANI. Furthermore, the present findings introduce a novel electrode material for high-performance supercapacitor application.

Polymer Derived Carbon Nanostructure Electrodes for Solid-State Supercapacitor

To resolve the energy storage challenges in portable electronic devices, flexible and solid-state supercapacitor are need of the hour. These devices are appealing as replacements to conventional lithium-ion batteries due to their high power density, long cycle life, chemical stability, and safety. We have synthesized sp2 hybridized porous carbon nanostructure using poly-paraphenylenediamine (PpPD) as a polymer and activated the prepared material via chemical activation for supercapacitor application. To the best of our knowledge, this is the first report on the demonstration of poly-paraphenylenediamine (PpPD) derived N-enriched porous activated carbon (PNAC) electrode with PVA/H2SO4 electrolyte for solid-state supercapacitor (SSC) device with high energy density and excellent cyclic stability. PNAC electrodes-based SSC electrochemical studies exhibit a high specific capacitance value of 39 F g−1 at 0.2 A g−1 current density. The solid-state supercapacitor attained energy density of 21.66 Wh kg−1 at power density of 199 W kg−1 and 0.2 A g−1 current density. The symmetric solid-state supercapacitor displays an outstanding cyclic stability up to 10,000 galvanostatic charge-discharge (GCD) cycles. High energy density and stability of the prepared device suggests it utility in portable energy storage application.