Effect of ZrO2 nanoparticles on phosphoric acid-doped poly (Ethylene imine)/Polyvinyl alcohol) membrane for medium-temperature polymer electrolyte membrane fuel cell applications

A high-level research is currently focused on the construction of polymer nanocomposite membranes with high proton conductivity (PC), peak power density (PD), and open circuit voltage (OCV) for polymer electrolyte membrane fuel cells (PEMFC) to substitute the commercial Nafion-211 membrane. The present study deals with the solvent-casting process for producing ZrO₂ nanoparticles (1–7 wt %) dispersed on phosphoric acid (PA) doped polyethylene imine and polyvinyl alcohol (PA-PEI/PVA) polymer nanocomposites (PNCs). ZrO₂ (5%) dispersed PA-PVA/PEI PNCs showed the highest ion-exchange capacity (IEC) of 2.94 mmol/g⁻¹ at room temperature (RT), and PC of 4.34 10⁻² S/cm⁻¹ at 120 °C. Experiments on the PNCs were carried out at 120 °C to evaluate their performance and usability in medium-temperature polymer electrolyte membrane fuel cells (MT-PEMFCs). The results indicate a practical and effective route for the fabrication of a composite membrane that has a semi-interpenetration network structure with abundant active protonated groups, and has future prospects and widespread application in MT-PEMFCs.     

One-step hydrothermal preparation of bi-functional NiS2/reduced graphene oxide composite electrode material for dye-sensitized solar cells and supercapacitors

To screen out suitable electrode materials and overcome the shortcomings of the existed electrode materials for the application in dye-sensitized solar cells and supercapacitors, NiS₂/reduced graphene oxide (NiS₂/rGO) composite material was prepared by a simple one-step hydrothermal method in this paper and applied in the field of both dye-sensitized solar cells and supercapacitors as electrode material. In an electrolyte of 6 M KOH, the NiS₂/rGO composite material with bilayer capacitance characteristics exhibited a high specific capacitance of 259.20 F g⁻¹ at the current density of 0.6 A g⁻¹, which was significantly higher than that of rGO (188.94 F g⁻¹). Moreover, at a current density of 2 A g⁻¹, the NiS₂/rGO composite material had 92.85% capacitance retention after 2000 cycles. When applied as counter electrode material for the dye-sensitized solar cells, the NiS₂/rGO composite material counter electrode exhibited a satisfactory photoelectric conversion efficiency (η) of 3.16% under standard simulated sunlight (AM 1.5 G), which was significantly higher than that of single rGO counter electrode (improved by 90.40%). The NiS₂/rGO composite electrode material prepared by a simple one-step hydrothermal method is a potential bi-functional composite electrode materials for both dye-sensitized solar cells and supercapacitors.     

Honeycomb micro/nano-architecture of stable β-NiMoO4 electrode/catalyst for sustainable energy storage and conversion devices

Multi-functionality is a highly desirable feature in designing new electrode material for both energy storage and conversion devices. Here, we report a well-integrated and stable β-NiMoO₄ that was fabricated on three dimensional (3D) nickel foam (NF) by a simple hydrothermal approach. The obtained β-NiMoO₄ with interesting honeycomb like interconnected nanosheet microstructure leads to excellent electrochemical activity. As an electrode for Supercapatteries, β-NiMoO₄–NF showed a high specific capacity of 178.2 mA h g⁻¹ (916.4 F g⁻¹) at 5 mA cm⁻² current density. Most importantly, the fabricated symmetric device exhibits a maximum specific energy of 35.8 W h kg⁻¹ with the power output of 981.56 W kg^-1 and excellent cyclic stability. In methanol electro-oxidation, the β-NiMoO₄ –NF catalyst deliver the high current density of 41.8 mA cm⁻² and much lower onset potential of 0.29 V with admirable long term stability. Apart from the above electrochemical activity, the β-NiMoO₄ –NF honeycomb microstructure demonstrates a promising non-noble electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and showed a considerable overpotential of 351 mV (OER) and 238 mV (HER). The attractive multifunctional electrochemical activity of β-NiMoO₄–NF could be originates from their unique honeycomb micro/nano structure which can acts as an “ion reservoir” and thus leads to superior energy storage and conversion processes.     

Novel organic–inorganic poly (3,4-ethylenedioxythiophene) based nanohybrid materials for rechargeable lithium batteries and supercapacitors

Synthesis and characterization of poly (3,4-ethylenedioxythiophene) (PEDOT) interleaved between the layers of crystalline oxides of V and Mo is discussed with special emphasis on their application potential as electrodes for rechargeable Li batteries and supercapacitors. The expansion of the interlayer spacing of crystalline oxides (for example, V₂O₅ causes expansion from 0.43 to 1.41 nm) is consistent with a random layer stacking structure. These hybrid nanocomposites when coupled with a large-area Li foil electrode in 1 M LiClO₄ in a mixture of ethylene and dimethylcarbonate (1:1, v/v), give enhanced discharge capacity compared to pristine oxides. For example a discharge capacity of ∼350 mAh g⁻¹, in the potential range 4.2–2.1 V (versus Li⁺/Li) is obtained for PEDOT–V₂O₅ hybrid which is significantly large compared to that for simple Li-intercalated V₂O_5. The improvement of electrochemical performance compared with that of pristine oxides is attributed to higher electric conductivity, enhanced bi-dimensionality and increased structural disorder. Although these conducting polymer-oxide hybrids delivered more than 300 mAh g⁻¹ in the potential range 1.3–4.3 V, their cycle life needs further improvements to realize their commercial potential. Similarly, the double layer capacitance of MoO₃ increases from ∼40 mF g⁻¹ to ∼300 F g⁻¹ after PEDOT incorporation in the interlayer gap of MoO₃ under similar experimental conditions and the nanocomposite displays intriguing effects with respect to electrochemical Li⁺ insertion. The PEDOT–MoO₃ nanocomposite appears to be a promising electrode material for non-aqueous type supercapacitors.     

Electrochemical investigation of MnO2 electrode material for supercapacitors

MnO₂ electrode material is synthesized by low temperature solid state reaction between KMnO₄ and MnCl₂. Effects of the KMnO₄:MnCl₂ molar ratio on the structure, morphology and electrochemical properties of the as-prepared sample were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. Results showed that the obtained MnO₂ is α-MnO₂, the average diameter is about 0.5-1.5 μm, which are constituted of nanoparticles of 20 nm. Under 100 mA g⁻¹, the specific capacitances of the prepared sample is 258.7, 219.6, 215.3, 198.5 and 209.5 F g⁻¹ at the KMnO₄/MnCl₂ molar ratio of 3:2, 2:1, 1:1, 1:2 and 2:3, respectively. And the MnO₂ sample with a KMnO₄/MnCl₂ molar ratio of 3:2 exhibits the best discharge capacitance and cycle performance. When the charge/discharge rate increases to 300 mA g⁻¹, the sample still remains initial discharge capacitance of 165.3 F g⁻¹, and the discharge capacitance is 145.9 F g⁻¹ after 200 cycles, the capacitance retention rate is 102.4% during the 20-200th cycles. Therefore, the MnO₂ sample is an excellent material for use in supercapacitors because of its large specific capacitance and good cycle performance.     

Fabrication of novel hybrid composite La2‐xCoxCuO4 electrode for high performance supercapacitors

Hybrid composites La_2‐xCo_xCuO₄ (x = 0, 0.1, 0.2, and 0.3) are prepared using one‐step simple hydrothermal route as electrodes for supercapacitors. The effect of varying cobalt content on morphological, structural, and electrochemical properties has been explored using X‐ray diffraction, scanning electron microscopy, and cyclic voltammetry, respectively. The structural parameters obtained by X‐ray diffraction showed tetragonal phase of hybrid composite without any evident impurity phases. The analysis of morphological properties suggested a strong correlation with electrochemical properties, for instance, a relationship between fabric porous structures and electrochemically active sites for redox reactions and intercalation/de‐intercalation processes. The hybrid composite electrodes demonstrated high specific capacitance of the order of 1304 F/g at 10 mV/s scan rate and exhibited decreasing trend on increasing scan rate. Hybrid composites were also tested for their ability as an electrode of high performance supercapacitors in different aqueous electrolytes, i. e, KOH, H₂SO₄, and Na₂SO₄ to optimize the best compatible electrolyte. The composite electrode material showed excellent cyclic stability and 98% capacitance retention for 1 A/g after 2000 cycles. The remarkable performance of hybrid composite electrode entails its potential for commercial applications of supercapacitors.     

Hydrothermal synthesis of nano-sized MnO2 supported on attapulgite electrode materials for supercapacitors

Among the electrode materials of supercapacitors, transition metal oxides have been widely used because of their low price, high theoretical capacitance and good cycle stability, and MnO₂ is one of the typical representative materials. However, the actual specific capacitance of MnO₂ is low because of its poor conductivity, easy agglomeration in the preparation process and large volume change in the process of repeated charge and discharge. Attapulgite can not only provide a large specific surface area for transition metal oxide materials, but also provide a skeleton on which nano-sized materials can be grown or dispersed. Therefore, the electrochemical performance of electrode materials can be improved by designing nanostructures and compounding a variety of materials with different properties. Herein, a new type of composites electrode material is prepared by simple one-step hydrothermal method. As an electrode material, the ATP-MnO₂ composites exhibited a high specific capacitance of 138.2 F/g at a current density of 0.5 A/g, which was 13.4% higher than that of pure MnO₂ nanoflowers. Under the current density of 3 A/g, the capacitance retention of ATP-MnO₂ composites was 89.4% after 5000 cycles.     

Effect of Nafion on the preparation and capacitance performance of polyaniline

With manganese dioxide (MnO₂) as the oxidant, perfluorinated sulfonic acid ion exchange resin (Nafion) as the doping agent and emulsifier, Nafion doped polyaniline (PANI-Nafion) was prepared by emulsion polymerization method. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were carried out to characterize the structure and morphology of PANI-Nafion. Symmetric redox supercapacitor was assembled with PANI-Nafion as active electrode material and 1.0 mol L⁻¹ H₂SO₄ aqueous solution as electrolyte. The electrochemical characteristics of these supercapacitors were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. These results show that the diameter of PANI-Nafion nanofiber is about 30 ∼ 40 nm and the pores between PANI-Nafion composite materials are distributed uniformly. The specific capacitance of PANI-Nafion electrode is about 385.3 F g⁻¹, which is higher than that of undoped PANI (235.8 F g⁻¹). After 1000 charge/discharge cycles the specific capacitance of PANI-Nafion electrode is 272.4 F g⁻¹, its capacity retention is 70.7%, which is significantly better than that of PANI electrode materials.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

A novel activated mesocarbon microbead(aMCMB)/Mn3O4 composite for electrochemical capacitors in organic electrolyte

A novel activated mesocarbon microbead(aMCMB)/Mn₃O₄ composite is successfully prepared for electrochemical capacitors. The morphology and crystal structure of the composite are investigated by scanning electron microscopy and X-ray diffraction. The electrochemical studies indicate that the aMCMB/Mn₃O₄ composite has ideal capacitive performance in 1.0 mol L⁻¹ LiPF₆(EC + DMC). A maximum specific capacitance of 178 F g⁻¹ is obtained for the composite via galvanostatic charge–discharge at a current density of 330 mA g⁻¹, and the specific capacitance of Mn₃O₄ is estimated to be as high as 445 F g⁻¹. The aMCMB/Mn₃O₄ composite material exhibits ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

Solvothermal synthesis of novel pod-like MnCo2O4.5 microstructures as high-performance electrode materials for supercapacitors

MnCo₂O_4.5 pod-like microstructures were successfully prepared through an initial solvothermal reaction in a mixed solvent containing water and ethanol, and combined with a subsequent calcinations treatment of the precursors in air. The total synthetic process was accomplished without any surfactant or template participation. The MnCo₂O_4.5 pods possessed a specific surface area as high as 73.7 m²/g and a mean pore size of 12.3 nm. The electrochemical performances were evaluated in a typical three-electrode system using 2 M of KOH aqueous electrolyte. The results demonstrated that such MnCo₂O_4.5 pods delivered a specific capacitance of 321 F/g at 1 A/g with a rate capability of 69.5% at 10 A/g. Moreover, the capacitance retention could reach 87% after 4000 cycles at 3 A/g, suggesting the excellent long-term cycling stability. Furthermore, the asymmetric device was fabricated by using MnCo₂O_4.5 porous pods as anode and active carbon as cathode. It could deliver a specific capacitance of 55.3 F g⁻¹ at 1 A g⁻¹ and an energy density of 19.65 W h kg⁻¹ at a power density of 810.64 W kg⁻¹. Such superior electrochemical behaviors indicate that the MnCo₂O_4.5 pods may be served as a promising electrode material for the practical applications of high-performance supercapacitors. The current synthesis is simple and cost-effective, and can be extended to the preparation of other binary metal oxides with excellent electrochemical properties.     

Spongy nano surface architecture of chemically grown BiVO4: High-capacitance retentive electrochemical supercapacitor

Design of nanostructured surface architecture is currently playing a vital role to enhance the energy storage capability of electrode materials and opening up a new era for future technologies through electrochemical supercapacitors. Present effort portrays the growth of nanostructured bismuth vanadate (BiVO₄) as an active electrode for supercapacitor application by using ease and industry scalable successive ionic layer adsorption and reaction (SILAR) method. Structural analysis reveals the development of orthorhombic structured BiVO₄ with spongy nano-pebbles like surface architecture. Synthesized BiVO₄ electrode yields remarkable capacitance of 707 F/g @3 mV/s scan rate. Faradaic and capacitive type contributions have been evaluated for in-depth understanding along with the estimation of electrochemical active surface area. Electrochemical impedance spectroscopy (EIS) analysis of BiVO₄ electrode exhibits 5.723 and 0.89 Ω cm² values of series and charge transfer resistances, respectively. Interestingly, BiVO₄ electrode delivers outstanding capacitive retention of 102% even at 3500 cycles, indicating its potential candidature for the advancement in high capability supercapacitors with excellent stability for the future technologies.     

One-step synthesis of nanoblocks@nanoballs NiMnO3/Ni6MnO8 nanocomposites as electrode material for supercapacitors

A novel nanoblocks@nanoballs NiMnO₃/Ni₆MnO₈ electrode material was synthesized by one-step solvothermal–hydrothermal method, followed by thermal annealing. At the same time, electrode materials with different nanostructure were prepared by changing the volume ratio of deionied water and ethylene glycol. The results show that different structure has been gained including nanospheres, nanosheets and nanoblocks. When the deionied water: ethylene glycol = 1:1 (nanoblocks@nanoballs NiMnO₃/Ni₆MnO₈ composite structure), the electrode material has a maximum specific surface area of 55.3 m² g⁻¹. The electrode material exhibited outstanding electrochemical performance with specific capacitance reached 494.4 F g⁻¹ at a current density of 1 A g⁻¹ as well as superior cycling performance of 88.0% capacitance retention after 5000 cycles at 3 A g⁻¹. Such excellent performance was due to the synergistic effective between the Ni₆MnO₈ nanoballs and NiMnO₃ nanoblocks. Nanoballs structure will increase in specific surface area and redox reaction active sites, and the blocks structure acts as a holder to improved the cycle performance. The NiMnO₃/Ni₆MnO₈ become a promising candidate as next-generation electrode material for high-performance supercapacitors.     

Multifunctional Co3O4/Ti3C2Tx MXene nanocomposites for integrated all solid-state asymmetric supercapacitors and energy-saving electrochemical systems of H2 production by urea and alcohols electrolysis

Co₃O₄/Ti₃C₂T_x MXene nanocomposites have been fabricated by vacuum filtration and hydrothermal-annealing methods, and their electrochemical performance were investigated for energy storage and conversion, systematically. As electrode materials, Co₃O₄/Ti₃C₂T_x MXene nanocomposites in 6 M KOH solution demonstrated the specific capacitance of 240.1 F g^?1 at 0.1 A g^?1 and the long-term cycle stability. The solid-state asymmetric supercapacitors exhibited an operating potential window of 1.4 V, a specific capacitance of 97.9 F g^?1at 0.25 A g^?1, an energy density of 95.9 Wh kg^?1 at a power density of 630.4 W kg^?1, and excellent long-term durability. Furthermore, the connected solid-state asymmetric supercapacitors inseries and parallels presented the promising practical applications. Besides, Co₃O₄/Ti₃C₂T_x nanocomposites displayed outstanding catalytic behaviors for energy-saving H₂ generation by urea and alcohols electrolysis. The electrolyzer in KOH + CH₃CH₂OH electrolyte required only 1.33 V potential to deliver the current density of 0.5 A g^?1. Especially, the elctrochemical system of H₂ production by The electrolyzer and the powered solid-state asymmetric supercapacitors based on Co₃O₄/Ti₃C₂T_x nanocomposites was constructed, demonstrating outstanding properties of H₂ production. Therefore, this study not only shows enormous potential of Co₃O₄/Ti₃C₂T_x nanocomposites as a portable power supply but also indicates its great opportunities in energy-saving H₂ production in practical applications.     

A bi-functional Co–Ni layered double hydroxide three-dimensional porous array electrode derived from ZIF-L(Co)@ZIF-L(Co,Ni) for oxygen evolution reaction and supercapacitors

Developing high-efficiency bifunctional materials for electro-catalysis and supercapacitors are urgently needed but challenging. Herein, we develop a self-supporting Co–Ni LDH electrode prepared by in-situ growing ZIF-L(Co)@ZIF-L(Co, Ni) on carbon paper followed by a pseudomorphic transformation. The optimized Co–Ni LDH/carbon paper electrodes (CN-2/CP) exhibit excellent electrochemical activity and stability in oxygen evolution reactions (OER) and supercapacitors. The CN-2/CP electrode displays a low overpotential of 230 mV at 10 mA cm^?2 and superior stability at 40-h chronopotentiometry for OER. For supercapacitor, the CN-2/CP electrode delivers a high specific capacitance of 1346 F g^?1 at 1 A g^?1 and maintains a capacitance of 88.5% after 7000 charge/discharge cycles at 20 A g^?1. Based on the physical and chemical characterization results, the high performance originates from the in-situ electrochemical conversion of metal hydroxide, improved conductivity, fast charge transfer at the interface and unique layered cross morphology providing more active sites.     

One-pot sonochemical synthesis of hierarchical MnWO4 microflowers as effective electrodes in neutral electrolyte for high performance asymmetric supercapacitors

In this article, manganese tungstate (MnWO₄) microflowers as electrode materials for high performance supercapacitor applications are prepared by a one-pot sonochemical synthesis. The crystalline structure and morphology of MnWO₄ microflowers are characterized through X-ray diffraction, field emission scanning electron microscopy. The electrochemical properties of the MnWO₄ microflowers are investigated using cyclic voltammograms, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The MnWO₄ microflowers as electrode materials possess a maximum specific capacitance of 324 F g⁻¹ at 1 mA cm⁻² in the potential window from 0 to +1 V and an excellent cycling stability of 93% after 8000 cycles at a current density of 3 mA cm⁻². An asymmetric supercapacitor device is fabricated using the MnWO₄ and iron oxide (Fe₃O₄)/multi-wall carbon nanotube as the positive and negative electrode materials, it can be cycled reversibly at a potential window at 1.8 V. The fabricated ASC device can deliver a high energy density of 34 Wh kg⁻¹ at a power density of 500 W kg⁻¹ with cycling stability of 84% capacitance retained after 3000 cycles. The above results demonstrate that MnWO₄ microflowers can be used as promising high capacity electrode materials in neutral electrolyte for high performance supercapacitors.     

Electrospun nickel oxide/polymer fibrous electrodes for electrochemical capacitors and effect of heat treatment process on their performance

Electrospinning is a versatile method for preparation of submicron-size fibers under ambient temperature. We demonstrate a new approach based on this method for preparing an electrode which consists of the fibers coated with nickel oxide (NiO) and acetylene black (AB) on their surfaces. The NiO/polymer fibrous electrodes show the electrochemical responses based on the electrochemical reaction of Ni(OH)₂ which is produced from NiO in alkaline aqueous solution. The capacitance of the test half cell with the as-prepared NiO/polymer fibrous electrode in 1 mol l⁻¹ KOH aqueous solution is 5.8 F g⁻¹ (per gram of NiO). Heat treatment (at 150 °C for 1 h in the air) of the NiO/polymer fibrous electrode increases the capacitance of the NiO/polymer fibrous electrode. The capacitance of the cell with the heat treated (HT) NiO/polymer fibrous electrode is 163 F g⁻¹ (per gram of NiO). SEM observation of the heat treated electrode suggests that partial melt of the fibers on the current collector forms the conducting passes and networks between the NiO particles and the collector and increases the specific capacity of the fibrous electrode.     

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks as high-performance electrode material for supercapacitors

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs¹ in rice husks and CO₂ promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO₂ in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO₂ formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm² at 4 mA/cm², the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors.     

Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

Chitosan/polyaniline/MWCNT nanocomposite fibers as an electrode material for electrical double layer capacitors

Polyaniline–MWCNT nanocomposite has successfully been synthesized on the surface of chitosan wet-spun fibers by chemical oxidative polymerization. Morphological characterization of the nanocomposite fibers was performed by scanning electron microscopy (SEM). Electrochemical properties of the nanocomposite fibers as electrode material for electrical double layer capacitors (supercapacitors) in 0.5 M H₂SO₄ were studied by cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) methods. The results showed that the nanocomposite fibers possess a specific capacitance of 14.48 F cm⁻² and a specific energy of 0.0013 Wh cm⁻² corresponding to a specific power of 0.011 W cm⁻². Total capacitance of the nanocomposite fiber consists of pseudocapacitance produced by the polyaniline and electrical double-layer capacitance produced by fiber|electrolyte interface and chitosan.