Macroporous defective tungsten oxide nanostructure electrodes deliver ultrahigh capacitance and remarkable long cyclic durability in LiCl electrolyte

Tungsten oxide (WO₃) has been considered as an fascinating candidate for supercapacitors (SCs) material because of its desirable physico-chemical properties and electrochemical behaviors. Nevertheless, it is still a significant challenge to enhance its electrochemical properties and stability. Herein, we report an electroreduction strategy to fabricate the macroporous defective tungsten oxide nanostructure (ER-WO₃) as a negative electrode material with outstanding electrochemical behavior and remarkable cycling durability in 5?M LiCl aqueous electrolyte, which attributes to the introduction of oxygen deficiencies. The ER-WO₃ electrode exhibits a large areal capacitance of 244.7?mF?cm^?2 and an ultrahigh gravimetric specific capacitance of 266.6?F?g^?1 at scan rate of 50?mV?s^?1. More importantly, the ER-WO₃ product also delivers an ultralong cyclic stability with 97.4% capacitance retention after 5000 cycles. Such these optimized properties of the ER-WO₃ nanostructure electrode will promote its applications in the field of science and technology.     

High power aqueous hybrid asymmetric supercapacitor based on zero-dimensional ZnS nanoparticles with two-dimensional nanoflakes CuSe2 nanostructures

Energy storage materials, particularly chalcogenides, are fascinating electrode materials for supercapacitors (SCs) because of their high capacitance, remarkable electrical conductivity, and multiple oxidation states contributed by numerous metal cations. Herein, a novel nanocomposite based on zinc sulfide and copper diselenide, denoted as (ZnS–CuSe₂), was prepared via a sonochemical-assisted method. The structural analysis revealed the cubic structure for pure ZnS, orthorhombic for CuSe_2, and co-existing cubic and orthorhombic phases for ZnS–CuSe₂ nanocomposites with high purity and crystallinity. The ZnS–CuSe₂ nanocomposite offered exceptional electrochemical performance with redox peaks from the CV analysis, and coupled with plateaus in the charge/discharge profile, confirming the faradaic energy storage properties with functional reversibility. Similarly, a high conductive feature of the ZnS–CuSe₂ composite was revealed by impedance study, with a minor charge transfer resistance than their bulk materials. A hybrid asymmetric supercapacitor (HASCs) composed of ZnS–CuSe₂//AC was constructed, which manifested an enlarged voltage window up to 1.7 V with capacitance of 95 F g⁻¹ and a maximum specific energy of 38 Wh kg⁻¹. Also, high power delivery was attained at 3927 Wkg^-1 when specific energy goes down to 12 Wh kg⁻ at 5 A g⁻¹. Interestingly, only 81.8% retention was left beneath when cycled to 8000 cycles, specifying decent stability of the ZnS–CuSe₂//AC HASCs.     

Sputtered titanium nitride films on nanowires Si substrate as pseudocapacitive electrode for supercapacitors

Titanium nitride (TiN) is widely used in electrode materials in fast charging/discharging supercapacitors (SCs) due to its outstanding conductivity. However, the low capacitance of the TiN electrode limits its further application in the SCs. Therefore, the reasonable design of the TiN electrode with high electrochemical and mechanical properties is still a challenge. In this paper, the silicon nanowires/titanium nitride electrode (Si NWs/TiN) is prepared by depositing TiN onto the etched Si nanowires by direct current magnetron sputtering. The Si NWs are prepared by etching silicon in 4.8 M HF/0.02 M AgNO₃ aqueous solution for different times (5 min, 15 min, 30 min, 60 min). The mechanism of the effect of etched silicon substrate morphology on the electrochemical performance of Si NWs/TiN electrode was studied. As the etching time increases, the differences of the TiN surface structure, lattice defects and surface chemical composition will change the capacitance performance and charge storage mechanism of the Si NWs/TiN electrode. The prepared Si₃₀ NWs/TiN electrode exhibits an outstanding specific capacitance as high as 113.55 F g⁻¹ at a scan rate of 5 mV s⁻¹ with 0.5 M H₂SO₄ solution as electrolyte. The specific capacitance of the Si₃₀ NWs/TiN electrode is as high as 7.5 times that of the electrode without etching at 100 mV s⁻¹. The Si₃₀ NWs/TiN electrode has an excellent cyclic stability performance, which the electrode has a decay rate of 12.4% after 2000 cycles. This indicates that the electrode has reliable stability. The electrode of the supercapacitor prepared by this method can open up a new way to expand the specific surface area of other transition metal nitride.     

Electrochemically synthesized graphene/polypyrrole composites and their use in supercapacitor

Composite films consisting of polypyrrole (PPy) and graphene oxide (GO) were electrochemically synthesized by electrooxidation of 0.1 M pyrrole in aqueous solution containing appropriate amounts of GO. Simultaneous chronoamperometric growth profiles and frequency changes on a quartz crystal microbalance showed that the anionic GO was incorporated in the growing GO/PPy composite to maintain its electrical neutrality. Subsequently, the GO was reduced electrochemically to form a reduced GO/PPy (RGO/PPy) composite by cyclic voltammetry. Specific capacitances estimated from galvanostatic discharge curves in 1 M H₂SO₄ at a current density of 1 A g^?1 indicated that values for the RGO/PPy composite were larger than those of a pristine PPy film and the GO/PPy composite. In the case of 6 mg mL^?1 GO for the preparation of GO/PPy, a high specific capacitance of 424 F g^?1 obtained at the electrochemically prepared RGO/PPy composite indicated its potential for use as an electrode material for supercapacitors.     

Synthesis of electrochemically-reduced graphene oxide film with controllable size and thickness and its use in supercapacitor

An electrochemical synthesis method of reducing graphene oxide (GO) under constant potential is reported. Electrochemical technique offers control over reaction parameters such as the applied voltage, electrical current and reduction time; whereas the desired size and thickness of the film can be pre-determined by controlling the amount of precursor GO deposited on the electrode with defined shape and surface area. This synthesis technique produces high quality electrochemically reduced GO (ERGO) film with controllable size and thickness. Electrochemical symmetrical supercapacitors based on ERGO films achieved a specific capacitance of 128 F/g with an energy density of 17.8 Wh/kg operating within a potential window of 1.0 V in 1.0 M NaNO₃. The supercapacitor was shown to be stable, retaining ca. 86% of the original specific capacitance after 3500 charge–discharge cycles. The results indicate that this simple synthesis technique for providing graphene-like materials has great potential in various applications such as energy storage.     

Nanosheet-like MoO3 and conductive PANI electrodeposited on flexible carbon cloth for self-supported solid-state supercapacitor electrode

In this paper, uniformly transition metal oxide (MoO₃) nanosheets were electrochemically deposited on flexible carbon cloth (CC), and then conductive polyaniline (PANI) was orderly wrapped around their surface by electrochemical polymerization. The morphology and structure of as-obtained self-supported PANI/MoO₃/CC electrode were investigated by FTIR, X-ray diffraction, Raman, scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy measurements in detail. Among all PANI/MoO₃/CC electrode, the self-supported PMC-3 (deposition time of 300 s) has high specific capacitance of 841.6 F g⁻¹ at current density of 0.5 A g⁻¹ in the three-electrode system, having specific capacitance of 595.7 F g⁻¹ even at 10 A g⁻¹. Novelty, the as-assembled symmetrical capacitor is flexible and convenient with power density of 199.93 W kg⁻¹ at the energy density of 9.69 Wh kg⁻¹ and the energy density of 3.88 Wh kg⁻¹ at power density of 4000 W kg⁻¹. Thus, the electrochemical properties of the self-supported PANI/MoO₃/CC electrode were significantly improved, and the self-supported electrodes are more competitive than other materials in practical application of clean energy storage systems.     

Influences of graphene oxide support on the electrochemical performances of graphene oxide-MnO2 nanocomposites

MnO₂ supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors. The structure and morphology of MnO₂-GO nanocomposites are characterized by X-ray diffraction, X-ray photoemission spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Nitrogen adsorption-desorption. As demonstrated, the GO fabricated from commercial expanded graphite (denoted as GO(1)) possesses more functional groups and larger interplane gap compared to the GO from commercial graphite powder (denoted as GO(2)). The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO₂, which lead to the fact that the loading amount of MnO₂ on GO(1) is much higher than that on GO(2). Elemental analysis performed via inductively coupled plasma optical emission spectroscopy confirmed higher amounts of MnO₂ loading on GO(1). As the electrode of supercapacitor, MnO₂-GO(1) nanocomposites show larger capacitance (307.7 F g^-1) and better electrochemical activity than MnO₂-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO₂ on GO(1) support.     

Recent Advances in SiO2 Based Composite Electrodes for Supercapacitor Applications

Supercapacitors (SCs) have been widely exploited as a promising energy storage system due to their unique merits, including fast charge/discharge rates, long-term cycling stability and low maintenance cost. Therefore, researchers are focused on designing novel nanostructures with high surface area, optimum pore size and volume, and porous structure are highly desirable. Silicon dioxide (SiO₂) has recently attracted enormous research attention as the electrode materials for SCs due to ease fabrication and integration possibility. However, due to the intrinsically poor electrical conductivity of metal oxides and the short diffusion distance of electrolytes into pseudocapacitor electrodes, only the surface of electroactive materials can effectively contribute to the total capacitance, while the large portion of material underneath the surface could hardly participate in the electrochemical charge storage process, leading to areal specific capacitance (ASC) values lower than expected. The coating of SiO₂ has been recognized as a possible route to reduce the resistance and increase durability. Still, even for coated electrodes, the performance has always been several orders of magnitudes below that of carbon-based SCs. The morphology, structure, and particle size of SiO₂ are related to the synthesis conditions and electrochemical performances. The thin films of SiO₂ nanostructures deposited on conductive substrates and their composites both shows good performance (binder free electrodes). SiO₂ and its composites display a large potential window for asymmetric SCs, delivering high energy density. More importantly, the design and development of composite materials with novel nanostructures are also effective ways to enhance the electrochemical properties of SCs. In this review, the research progress of SiO₂ based composite electrodes for SCs are briefly reviewed. Consequently, the possible developmental direction, challenges, and opportunities for SiO₂ based composite are also discussed.

     

A new As3Mo8V4/PANi/rGO composite for high performance supercapacitor electrode

Herein, [As₂^IIIAs^VMo₈^VIV₄^IVO₄₀]₂[Cu^ICu₂^II(pz)₄]₂·9H₂O/polyaniline/reduced graphene oxide (pz = pyrazine, abbreviated to As₃Mo₈V₄/PANi/rGO) composite is first assembled, characterized and systematically explored for its supercapacitor performance. As₃Mo₈V₄/PANi/rGO composite shows a exceptional specific capacitance (2351 F g^?1 at 1 A g^?1) and outstanding cyclic stability (96.9% after 5000 cycles). The symmetric supercapacitor exhibits high specific capacitance of 1295 F g^?1 at 1 A g^?1 and excellent energy density of 88.1 Wh kg^-1 at power density of 349.6 W kg^-1, while maintaining a notable capacitance retention of 85.7% after 5000 cycles at 2 A g^-1. The above results confirm the potential application of As₃Mo₈V₄/PANi/rGO composite in energy storage devices.     

Graphite–graphite oxide composite electrode for vanadium redox flow battery

A graphite/graphite oxide (GO) composite electrode for vanadium redox battery (VRB) was prepared successfully in this paper. The materials were characterized with X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The specific surface area was measured by the Brunauer–Emmett–Teller method. The redox reactions of [VO₂]⁺/[VO]²⁺ and V³⁺/V²⁺ were studied with cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the electrochemical performances of the electrode were improved greatly when 3 wt% GO was added into graphite electrode. The redox peak currents of [VO₂]⁺/[VO]²⁺ and V³⁺/V²⁺ couples on the composite electrode were increased nearly twice as large as that on the graphite electrode, and the charge transfer resistances of the redox pairs on the composite electrode are also reduced. The enhanced electrochemical activity could be ascribed to the presence of plentiful oxygen functional groups on the basal planes and sheet edges of the GO and large specific surface areas introduced by the GO.     

Electrochemical behavior of CuO/rGO nanopellets for flexible supercapacitor,non-enzymatic glucose,and H2O2 sensing application

In the present article, graphene oxide (GO) sheets and monoclinic copper oxide (CuO) nanocrystals are connected with each other and result in the formation of CuO/rGO nanopellets, and these nanopellets synthesized using coprecipitation method. The nanopellet structured CuO/rGO composite on carbon cloth, which act as current collector exhibits specific capacitance of 188 F g^?1 at a current density of 0.2 A g^?1 and up to 96.3% capacity retention after 2000 charge-discharge cycles. It shows a maximum energy density of 7.32 Wh kg^?1 and power density of 53 W kg^?1. The glucose sensing characteristics of CuO/rGO nanopellet is investigated on carbon cloth and ITO substrate. It shows glucose sensitivity of 0.805 mA mM^?1 cm^?2 and 0.2982 mA mM^?1 cm^?2 for a bundle like structured CuO/rGO composite on carbon cloth and ITO substrate, respectively. Further H₂O₂ sensing is studied on ITO substrate, which manifests H₂O₂ sensitivity of 84.39 μA mM^?1 cm^?2. The results indicate that nanopellet structured CuO/rGO composite could be a promising electrode material for supercapacitor, glucose, and H₂O₂ sensor.     

Raspberry-like Ni/NiO/CoO/Mn3O4 hierarchical structures as novel electrode material for high-performance all-solid-state asymmetric supercapacitors

Hybrid transitional metals oxides have been attracted more and more attention in the field of supercapacitors. However, the design of structure and composition of materials is always a challenge due to tedious preparation process and difficult structure construction. Based on above issue, we construct novel raspberry-like Ni/NiO/CoO/Mn₃O₄ hierarchical structures (NNCMs) with excellent electrochemical performances by one-step hydrothermal process in this work. The introduction of metallic Ni and well-designed hierarchical structures can result in well improved conductivity for electrode material, sufficient channels and active sites for electrolyte ions to enter and contact with electrode material. The NNCMs-16 electrode exhibits a high specific capacitance of 1964 F g⁻¹ and superior cycling stability (95% of initial specific capacitance after 10000 cycles). The assembled NNCMs-16//AC device delivers outstanding energy densities of 70.4 Wh kg⁻¹ at power densities of 794.5 W kg⁻¹. Thus, the raspberry-like NNCMs-16 hierarchical structures can be regarded as promising materials for practical supercapacitors and this work also provides a valuable reference for the preparation and application of high performance electrode materials.     

Excellent performance MWCNTs-GONRs/Ni(OH)2 electrode for outstanding supercapacitors

Due to the unconventional properties of MWCNTs-GONRs (multiwalled carbon nanotubes-graphene oxide nanoribbons), we have tried to use it as a carbon resource for supercapacitors. MWCNTs-GONRs/Ni(OH)₂ electrode was obtained by hydrothermal method. Velvet α-Ni(OH)₂ was prepared above NF (nickel-foam) loaded with MWCNTs-GONRs. This layered design can effectively promote the diffusion of ions and increase the active site for MWCNTs-GONRs/Ni(OH)₂ electrode, thus enhancing the electrochemical performance. The electrode exhibits extraordinary electrochemical performances in electrochemical testing, such as supernal specific capacitance (1713.2 F g⁻¹) and prominent working time. In addition, supercapacitors was assembled with MWCNTs-GONRs/Ni(OH)₂ and active carbon as materials. Which represents a prominent energy density (41.23 Wh kg⁻¹), high power (6.80 kW kg⁻¹) and prominent cycling stability property (95.18%, 3000 times). The electrode prepared in this work provides a clue to enlighten people for energy storage.     

Porous carbon nanosheet with high surface area derived from waste poly(ethylene terephthalate) for supercapacitor applications

Converting waste plastics into valuable carbon materials has obtained increasing attention. In addition, carbon materials have shown to be the ideal electrode materials for double-layer supercapacitors owing to their large specific surface area, high electrical conductivity, and stable physicochemical properties. Herein, an easily operated approach is established to efficiently convert waste poly(ethylene terephthalate) beverage bottles into porous carbon nanosheet (PCNS) through the combined processes of catalytic carbonization and KOH activation. PCNS features an ultrahigh specific surface area (2236 m² g⁻¹), hierarchically porous architecture, and a large pore volume (3.0 cm³ g⁻¹). Such excellent physicochemical properties conjointly contribute to the outstanding supercapacitive performance: 169 F g⁻¹ (6 M KOH) and 135 F g⁻¹ (1 M Na₂SO₄). Furthermore, PCNS shows a high capacitance of 121 F g⁻¹ and a corresponding energy density of 30.6 Wh kg⁻¹ at 0.2 A g⁻¹ in the electrolyte of 1 M TEATFB/PC. When the current density increases to 10 A g⁻¹, the capacitance remains at 95 F g⁻¹, indicating the extraordinary rate capability. This work not only proposes a facile approach to synthesize PCNS for supercapacitors, but also puts forward a potential sustainable way to recycle waste plastics and further hopefully mitigates the waste plastics-related environmental issues. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48338.     

Wood Pulp Fiber Wrapped by Fish-Scale Graphene as Flexible and Free-Standing Supercapacitor Electrode

Poplar wood pulp was adopted as both frame and precursor for the synthesis of pulp fiber (PF)/reduced graphene oxide composite via a simple and low-cost method. In this method, the PF based on graphene (PFG) composite film electrode was prepared by a simple vacuum filtration process with various ratios (PF: reduced graphene oxide (RGO)?=?5:1, PF:RGO?=?5:2, PF:RGO?=?5:3, PF:RGO?=?5:4, PF:RGO?=?5:5). In terms of special structures, the PFG can be used as electrodes without metal-collector, adhesives, and additives. The optimal ratio (PF:RGO?=?5:4) film electrode displayed a high areal-specific capacitance of 683 mF/cm² at 1?mA/cm² with a mass of 5.3?mg/cm² (specific capacitance of 129?F/g) and good cycling stability (87.5% capacitance retention after 10,000 cycles at 5?mA/cm²) as well as excellent rate capability and high flexibility (suitable for any angle, even 180°). Moreover, the device could possess a maximum energy density of 47.71?μWh/cm² and a maximum power density of 1251?μW/cm². These results suggest that the composite PGF film is a promising electrode material.     

Nano-porous carbon materials derived from different biomasses for high performance supercapacitors

Nano-porous carbon materials derived from various natural plants are fabricated by a facile, cost-effective and efficient approach. The influence of well-dispersed intrinsic elements in different precursors and chemical activation process under different temperatures on the morphology, surface chemistry, textural structures and electrochemical performance have been studied and analysed in detail. These as-prepared nano-porous carbons possess high accessible surface area (685.75–3143.9 m² g⁻¹), well-developed microporosity and high content of naturally-derived heteroatom functionalities (16.43 wt%). When applied as electrode materials for supercapacitors in a three-electrode system with 6 M KOH, the obtained nano-porous carbons derived from lotus leaves at 700^oC possess a high specific capacitance of 343.1 F g⁻¹ at 0.5 A g⁻¹ and a capacitance retention of 96.2% after 10000 cycles at 5 A g⁻¹. The assembled symmetrical supercapacitor presents a high energy density of 24.4 Wh kg⁻¹ at a power density of 224.6 W kg⁻¹ in Na₂SO₄ gel electrolyte. This work provides guiding function for unified and large-scale utilization of agricultural biomass waste. The obtained sustainable activated carbon products can be used in diverse applications.     

Polypyrrole-wrapped NiCo2S4 nanoneedles as an electrode material for supercapacitor applications

In this study, dicobalt tetrasulfide (NiCo₂S₄) nanoneedles were successfully synthesized by a two-step hydrothermal method on nickel foam. A layer of polypyrrole (PPy) was further wrapped on the surface of the NiCo₂S₄ nanoneedles by in-situ polymerization. The obtained NiCo₂S₄@PPy composite was investigated for supercapacitor applications, which exhibited a capacitance of 1842.8 F g^?1 at 1 A g^?1. An asymmetric supercapacitor device fabricated with an activated carbon negative electrode and NiCo₂S₄@PPy positive electrodes exhibited an energy density of 41.2 Wh kg^?1 at 402.2 W kg^?1 with a high charge–discharge cycling stability (92.8% after 5000 cycles). These results demonstrate that NiCo₂S₄@PPy electrodes have broad application prospects as energy storage electrode materials.     

Simultaneously morphology and phase controlled synthesis of cobalt manganese hydroxides/reduced graphene oxide for high performance supercapacitor electrodes

Cobalt manganese hydroxides with well-defined nanowire morphology (CoMn-HW) is scalable fabricated by adjusting solution contents, Mn/Co ratio and alkaline species. To further improve the conductivity of CoMn-HW, GO is introduced during fabrication process and reduced to rGO according to the high temperature and alkali atmosphere. By optimizing the adding mass of rGO, CoMn-HW/rGO with sandwiched like structure is successfully synthesized for supercapacitor electrode. The composite delivers a high specific capacitance of 784 F g⁻¹ at current density of 0.5 A g⁻¹, good rate capability (84.2% capacitance retention after current density increase 10 times). Moreover, an asymmetric supercapacitor with CoMn-HW/rGO10 as the positive electrode and active carbon as the negative electrode, is assembled and delivers a maximum energy density of 38.3 Wh kg⁻¹ and power density of 8000 W kg⁻¹, representing its potential in energy storage and conversion systems.     

Ultrasonically dispersed multi-composite strategy of NiCo2S4/Halloysite nanotubes/carbon: An efficient solid-state hybrid supercapacitor and hydrogen evolution reaction material

Herein, we have developed a novel hybrid material based on NiCo₂S₄ (NCS), halloysite nanotubes (HNTs), and carbon as promising electrodes for supercapacitors (SCs). Firstly, mesoporous NCS nanoflakes were prepared by co-precipitation method followed by physically mixing with HNTs and carbon, and screen printed on nickel foam. After ultrasonication, a uniform distribution of the Carbon/HNTs complex was observed, which was confirmed by surface morphological analysis. When used as electrode material, the NCS/HNTs/C hybrid displayed a maximum specific capacity of 544 mAh g^?1 at a scan rate of 5 mV s^?1. Later, a solid-state hybrid SCs was fabricated using activated carbon (AC) as the negative and NCS/HNTs/C as the positive electrode (NCS/HNTs/C//AC). The device delivers a high energy density of 42.66 Wh kg^?1 at a power density of 8.36 kW kg^?1. In addition, the device demonstrates long-term cycling stability. Furthermore, the optimized NCS, NCS/HNTs, and NCS/HNTs/C nanocomposites also presented superior hydrogen evolution reaction (HER) performance of 201, 169, and 116 mV in the acidic bath at a current density of 10 mA cm^?2, respectively. Thus, the synthesis of NCS/HNTs/C nanocomposite as positive electrodes for hybrid SCs opens new opportunities for the development of next-generation high energy density SCs.     

Synthesis and characterization of polypyrrole/graphitic carbon nitride/niobium pentoxide nanocomposite for high-performance energy storage applications

Graphitic carbon nitride (GCN) has been employed as a supercapacitor electrode because of its high carbon-to-nitrogen ratio and flexible structure. However, its low surface area and poor conductivity continue to be obstacles for practical usage. GCN's electrochemical characteristics are enhanced by the hybrid structure it forms with polypyrrole and Nb₂O₅. The synthesized polypyrrole (Ppy)/GCN/niobium pentoxide (Nb₂O₅) (Ppy/GCN/Nb₂O₅) nanocomposite electrode was tested for supercapacitance by cyclic voltammetry (CV) and Alternating current impedance techniques in 6 M Potassium hydroxide(KOH) electrolyte. The Ppy/GCN/Nb₂O₅ is linked to a network of agglomerated GCN and Nb₂O₅ nanoparticles with additional spherical shapes. The specific capacitance of Ppy/GCN/Nb₂O₅ was determined to be 1177 Fg⁻¹ at a current density of 5 Ag⁻¹. The Ppy/GCN/Nb₂O₅ electrode in KOH has average specific energy and specific power densities of 33 Wh kg⁻¹ and 2991 W kg⁻¹, respectively. The electrode showed excellent capacitance-retention ability of 97% after 10,000 cycles. The results demonstrate the high stability and efficient performance of the Ppy/GCN/Nb₂O₅ electrode employed in supercapacitors. The performance of the Ppy/GCN/Nb₂O₅ electrode was found to be superior to those reported for other carbon-based materials.