No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Synthesis of different new copolyimides and influence of different molar ratios of diamines and dianhydride on pseudocapacitance performance of p-type conductive polymer
Abstract
In the present work, poly ortho aminophenol/copolyimides (POAP/PI) composites were prepared using PIs together with POAP. PIs were synthesized using different molar ratios of diamines and dianhydride by polymerization method. Different electrochemical methods including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) were applied to study system performance. Presence of PIs in the composite films improved mechanical and electrochemical performance of the p-type conductive polymer. This study reveals that POAP/PI with high specific capacitance and long cycle-life is suitable for application in energy storage materials.
... It is evident that Whole curves are triangularshaped, linear, symmetric, and relatively sharp. Furthermore, the reversible performance, elevated columbic efficiency, and excellent capacitor behavior of samples is the probable result of the equivalent durations of charge and discharge [44,107,108]. According to discharge curves, Eq. (1) [109] is reported for the calculation of specific capacitance: ...
Adenosine triphosphates (ATP) are excellent energy-carrying molecules due to their phosphate functional groups that link through phosphodiester bonds, while halloysite nanotubes (HNTs) are layered mineral materials which exist naturally and have a large number of active sites for energy storage reinforcement. The use of HNTs and ATP in combination will provide a new approach to producing advance electrode materials for energy storage devices. Herein, a simple and cost-effective chemical method is introduced to fabricate a composite electrode of functionalized halloysite nanotubes (FHA) loaded with a pyridinium-based ionic liquid (PyPS) and conductive polymer, poly ortho amino phenol (FHA-PyPS-POAP) for use in supercapacitor. The prepared FHA-PyPS-POAP electrode exhibited outstanding electrochemical behavior with a capacitance being up to 626 F g⁻¹ at 1 A g⁻¹ in a 1M Na2SO4 electrolyte while preserving remarkable rate capability and indicating superior cycle stability. Besides, the FHA-PyPS-POAP electrodes employed in the two-electrode system with a capacitance of 306 F g⁻¹ at 0.5 A g⁻¹ and possessed an energy density of 20.8 W h kg⁻¹ at 350 W kg⁻¹. Also, the symmetrical supercapacitor shows capacitance retention remaining 93.9% for FHA-PyPS-POAP//FHA-PyPS-POAP at 8 A g⁻¹ over 5000 cycles. Thus, these promising findings demonstrated a high potential as a significant application in developing energy storage devices with enhanced energy and power concentrations.
... The introduction of a second monomer in the form of rings to the polymer matrix, by establishing connections with the basic conductive polymer, is a very effective method. This can be achieved by copolymerization with monomers even if they are insulating, provided that the alternation exists between the single and double bonds along the chemical skeleton obtained at the end [9][10][11][12]. ...
An effective technique is proposed in this study to synthesize a novel polymer, based on the copolymerization of pyrrole with a synthesized monomer (phenylazepane-2-one), combining the character of both conductivity and solubility. The reaction was cationically catalyzed, using an acid exchanged clay (Maghnite-H⁺) as an ecological catalyst. The reaction synthesis of poly[(phenylazepane-2-one)-co-(pyrrole)] abbreviated poly(PAP) has been carried out in dichloromethane. The reaction yield was 85% at a temperature of 25 °C for 4 h using 4% of catalyst. Chemical structures have been characterized by proton and carbon nuclear magnetic resonance (¹H-NMR and ¹³C-NMR), ultraviolet/visible spectroscopy (UV–Vis) and Fourier transform infrared spectroscopy (FT-IR). Thermal properties have been evaluated by differential scanning calorimetry and thermal gravimetric analysis, showing the thermal stability of the poly(PAP) up to 333 °C. Solubility tests confirmed the solubility of poly(PAP) in various common solvents. The indirect band-gap was found 1.22 eV using Tauc’s formula. The semiconductor behavior poly(PAP) has been proven by the evolution of ac electrical conductivity and dielectric properties as a function of frequency and temperature. These new properties allow direct application of poly(PAP) on all desired surfaces rather than conventional materials.
Graphic abstract
... Recently, supercapacitors have been widely employed in many research areas due to unique properties and thus, the widespread acceptance of ultracapacitors has led to the introducing several methods to enhance their performance including constructing hybrid systems, modification of surface electrodes, and new designed/synthesized electrode materials (Fig. 4). To improve the electrochemical feature of supercapacitors, various class of carbon-based materials such as graphene, carbon nanotubes, activated carbon, carbon aerogel and carbon black have been terrifically used in supercapacitors [68][69][70][71][72][73][74][75][76]. Besides, the new type of metal organic frameworks with ability of structural tailoring, high surface area, and permeability to guest molecules, have attracted enormous attentions to use in supercapacitors. ...
Energy conversion and storage devices (ECSDs) made from clean, green and eco-friendly agricultural/bio waste is achieving more attention of researchers/scientists due to its recyclability, low cost, sustainability, and excellent supercapacitance performance. The role of green electrolytes (GEs) (such as, quasi/novel solid), separators, current collectors, and electrode materials (for instance, biomass waste-derived from activated carbon (AC), reduced graphene-oxide (rGO), metal-oxides (MOs), metal-organic frameworks (MOFs), and conducting polymers (CPs)) for ECSDs is highlighted in this chapter. The depletion of energy supplies and trashing of agricultural waste has become a worldwide concern, throbbing the world’s economy and ecosystem via the fuel crisis and pollution and hence the idea of Green/Eco-Friendly Supercapacitors (GSs) is pointed out in this chapter. In the last section, the future research prospects and challenges of green electrode-electrolyte based ECSDs at industrial scale for energy sector are also projected, keeping in view their health related concerns and disposal.
With the increasing advancement of knowledge and the widespread use of electronics, the demand for more efficient energy storage devices and materials has increased dramatically. Poly ortho-aminophenol and its composites as the energy storage materials are reviewed in this article. The capacitive properties (specific capacitance, specific energy, specific power, number of charging-discharging cycles, and retention capacitance) of all these composites are fully listed as well as compared with other electrode materials. Electrochemical test diagrams (CV, GCD, and EIS) of some of these materials have been carefully studied. The data show that POAP composites have excellent electrochemical performance compared to pure POAP and other composites. These electrodes have also been tested in the actual devices and have shown excellent performance. Also, the morphological properties and structure of composite (SEM, TEM, BET, Fractal dimension, components) of these electrodes have been reviewed. The synergistic effect between the components has been reported. This polymer has a special electrocatalytic effect that can be used to design innovative electrodes with excellent performance and surface modification. Finally, a summary and insight into future plans are provided. In general, these composites showed excellent electrochemical performance and morphological properties, which shows the high potential of these materials in the application of supercapacitor electrodes.
Herein, high-purity TbMn2O5 nanostructure has been synthesized by the electrochemical technique. Different mechanical properties such as particle size, texture coefficient and lattice constant, were obtained by Nelson-Riley functions, Scherrer's equation, Williamson-Hall methods and compared with computational and XRD data. The projector augmented-wave method (PAW) directly from the Kohn-Sham density functional was used to carry out all post-processing calculations including band structure and density of state (DOS) estimations along with the band gap. Then, hybrid Poly ortho aminophenol (POAP)/TbMn2O5 films, acting as active materials in energy storage device, were prepared through POAP electropolymerization in the presence of TbMn2O5 nanoparticles in order to enhance the electrochemical performance of the POAP film. In addition, POAP/TbMn2O5 composites exhibited good cycling stability, retaining 89% of the capacitance after 1000 charge/discharge cycles, owing to the high mechanical strength of the TbMn2O5.
In this research work, copolyimides (PIa,b) were synthesized by chemical routs. We used perylene-3,4,9,10-tetracarboxylic dianhydride and synthesized diamines (DAa,b) containing thiazole ring as monomers to obtain PIa,b which were characterized by ¹HNMR and FTIR spectroscopies. We prepared POAP/PIa and POAP/PIb by depositing poly ortho amino phenol (POAP) as conductive polymer on the surface of PIa,b via in situ electropolymerization. To evaluate the effect of the PIa,b in terms of the electrochemical performance of composites, we used galvanostatic charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. The specific capacitance of 207.2 and 322.4 F/g are obtained for POAP/PIa and POAP/PIb, respectively. All these evidences prove that POAP/PI composites have long cycle life as well as high specific capacitance, which are indicative for being a good candidate in terms of application in supercapacitors.
Graphic abstract
Open image in new window
Herein, high-purity Y2O3 nanopowder has been synthesized by the electrochemical method. The crystal structure of the compound has been investigated by means of X-ray diffraction (XRD). In order to evaluate the bonding characteristics of the obtained compound, Fourier transform infrared spectroscopy (FTIR) was carried out. Morphological properties of the nanopowders were examined through field emission scanning electron microscopy (FE-SEM). Furthermore, thermal studies were investigated through the thermogravimetric analysis (TGA). Not only from the XRD spectrum but also using the Nelson-Riley functions, various surface parameters referring to Y2O3 nanoparticles, e.g. particle size, texture coefficient and lattice constant, were determined. Additionally, Modified Scherer's Scherrer,s formula (Williamson-Hall-isotropic strain model) was utilized to predict microstrain introduced into electrosynthesized Y2O3 nanoparticles. Full potential periodic density functional theory was used to derive detailed structural and electronic information of Y2O3 crystal. Revised Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional was used for bulk structure relaxation and all post-processing calculations such as band structure and density of state (DOS) calculations were done with Heyd-Scuseria-Ernzerhof (HSE) method. Then, hybrid POAP/Y2O3 films, acting as active electrodes in electrochemical supercapacitor applications, were prepared through poly orthoaminophenol (POAP) electropolymerization in the presence of Y2O3 nanoparticles in order to enhance the electrochemical performance of the conductive polymer. The energy storage behavior observed for the prepared composite film can be attributed to synergistic effect existing between Y2O3 nanoparticles and the conductive polymer.
Significant electrochemical properties improvement of poly ortho aminophenol (POAP) as conductive polymer and simultaneously as active electrode of electrochemical supercapacitor through fabricated POAP composite film in the presence of biopolymer chitosan (CTS) with porous structure was obtained. Nanocomposite morphology and information about POAP‐CTS interaction in the synthesized thin films were examined via scanning electron microscope. The surface area that depends on the porosity morphology was examined by Brunauere‐Emmette‐Teller (BET) analysis. Accordingly, the BET surface area, mean pore diameters, and single point total pore volume were measured as 39.044 m2 g−1, 19.68 nm, and 0.192 cm3 g−1, respectively. Electrochemical measurements like galvanostatic charge‐discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy were investigated to examine the performance of the electrosynthesized composite (POAP/CTS) film. And also, the specific charge obtained as 345 F/g for POAP/CTS. In this work, a new considerable efficient polymeric composite in electrochemical redox capacitors with considerable advantages including ease synthesis, high active surface area, and stability in an aqueous electrolyte was introduced. Analysis of the quantum theory of atoms‐in‐molecules results shows that the chitosan system can be categorized into n‐type‐like (electron density donor) and p‐type‐like (electron density acceptor) sections and thus the parallel (in xy/yx plan) and perpendicular (in xz/yz plan) intramolecular sections have different electronic behaviors/electro‐chemical characterizations in molecule.
Sm³⁺-doped magnetite (Fe3O4) nanoparticles were synthesized through a one-pot facile electrochemical method. In this method, products were electrodeposited on a stainless steel (316L) cathode from an additive-free 0.005 M Fe(NO3)3/FeCl2/SmCl3 aqueous electrolyte. The structural characterizations through X-ray diffraction, field-emission electron microscopy, and energy-dispersive X-ray indicated that the deposited material has Sm³⁺-doped magnetite particles with average size of 20 nm. Magnetic analysis by VSM revealed the superparamagnetic nature of the prepared nanoparticles (Ms = 41.89 emu g⁻¹, Mr = 0.12 emu g⁻¹, and HCi = 2.24 G). The supercapacitive capability evaluation of the prepared magnetite nanoparticles through cyclic voltammetry and galvanostat charge–discharge showed that these materials are capable to deliver specific capacitances as high as 207 F g⁻¹ (at 0.5 A g⁻¹) and 145 F g⁻¹ (at 2 A g⁻¹), and capacity retentions of 94.5 and 84.6% after 2000 cycling at 0.5 and 1 A g⁻¹, respectively. The results proved the suitability of the electrosynthesized nanoparticles for use in supercapacitors. Furthermore, this work provides a facile electrochemical route for the synthesis of lanthanide-doped magnetite nanoparticles.
Poly(3,4-ethylenedioxythiophene) polymer film (PEDOT-IL) was electrosynthesized in the ionic liquid (IL) 1-ethyl-3-methylimidazolium hydrogen sulphate (EMIMHSO4) medium, which also contains 0.1 M LiClO4 in ACN. For comparison reasons in terms of structure and electrode capacitance performance, PEDOT film was also synthesized electrochemically without IL. The SEM results show that PEDOT-IL film has more porous surface and fine textures with nanometer-diameter than PEDOT polymer. Different electrochemical methods including galvanostatic charge–discharge (CD) experiments, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were carried out to investigate the applicability of the system as a redox supercapacitor for both polymers. PEDOT-IL electrode shows higher optimum specific capacitance than PEDOT film. Additionally, the symmetrical supercapacitor was assembled from two PEDOT-IL electrodes in LiClO4/ACN medium and exhibited a maximum specific capacitance of 107 F g⁻¹, an energy density of 11.5 Wh kg⁻¹ at a power density 13 kW kg⁻¹, and an excellent cycle life of 96% specific capacitance retention after 1000 cycles.
Magnetic functional graphene oxide (MFGO) has been synthesized in this work using FeCl4⁻ magnetic anion paired with 1-methyl imidazolium cation. Hybrid poly ortho aminophenol (POAP)/MFGO films have then been prepared via POAP electropolymerization in the presence of MFGO nanosheets, serving as active electrodes for electrochemical supercapacitors. The functional group in MFGO plays a major part in atomic scale charge/energy transfer and consequently intramolecular electrochemical phenomena in MFGO systems, as shown by the theoretical results. POAP/MFGO composite films have been characterized by surface and electrochemical analyses. The performance of the system has been investigated by various electrochemical methods such as galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy. Novel nanocomposite compounds have been developed in this work for electrochemical redox capacitors. The advantages of these compounds include simple synthesis method, high active surface area and stability in aqueous electrolytes.
In this paper firstly, Cu (II)-based metal-organic framework (MOF; Cu-bipy-BTC, bipy = 2,2′-bipyridine, BTC = 1,3,5-tricarboxylate) was synthesized using chemical approach and then fabricated hybrid poly ortho aminophenol (POAP)/Cu-bipy-BTC films by electropolymerization of POAP in the presence of Cu-bipy-BTC nanoparticles to serve as the active electrode for electrochemical storage device. Surface analysis and electrochemical analysis have been used for characterization of POAP/Cu-bipy-BTC composite film. Different electrochemical methods including galvanostatic charge–discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area, and stability in an aqueous electrolyte.
Mn3O4 nanorods with secondary plate-like structures were prepared through precipitation from a0.005M manganese chloride bath, under the applyingdirect current mode (i=2 mA cm-2). The structural analysisthrough XRD and FTIR confirmed that the deposited nanopowder haspure monoclinic phase of Mn3O4. Further morphological assessment through SEM proved the product to have the Mn3O4nanorods in large quantity, which constructed the secondary plate-like building blocks. Cyclic voltammetric and charge-discharge experiments on the product indicated the prepared Mn3O4to possess high specific capacitance (SC) values of 298 F g−1, as well as an outstandingly durable cycling stability (95.1% of initial capacity after discharging 1000 cycles).
A facile and scalable method is used in this study for oxidation polymerization and catalytic carbonization method to prepare three-dimensional hierarchically structured nitrogen-doped carbon nanohybrids (3D N-CNs) which could be used as the efficient electrode material for supercapacitors. In the synthesis process, citric acid plays an important role in controlling the shape of nitrogen-doped carbon nanohybrids. As an electrode material for supercapacitors, the 3D N-CNs-2 possess high specific capacitance of 274.6 F g−1 at 0.5 A g−1, excellent rate capability (ca.75.5 % retention along with the current density increasing from 0.5 to 20 A g−1) in 6 M KOH aqueous solution. The electrochemical performance can be ascribed to the synergistic effects of the hierarchical nanostructure and nitrogen doping, suggesting that the 3D N-CNs-2 as novel electrode materials may have the potential applications in high-performance energy storage devices.
To enhance the electrochemical performance, a conventional activated carbon supercapacitor is modified by adopting potassium-polyacrylate (PAAK) electrolyte additive on a glass fiber separator and by fabricating the activated carbon electrode on nickel foam instead of on conventional nickel foil as a current collector. The glass fiber separator plays the role of self-supporting PAAK-KOH hydrogel electrolyte with superior ionic conductivity. Moreover, the adoption of nickel foam strengthens the close contact between the active material and the current collector, reducing the interfacial resistance between electrode and electrolyte. As a result, the combination of glass fiber separator and nickel foam substrate can contribute to a great increase in the specific capacitance, to a value of over 200 F g−1, and to an enhancement of the high-rate capability of activated carbon supercapacitors.
Graphical abstract
A poly(amide-imide) (PAI) bearing imidazole groups on the polymer chain was synthesized via direct polycondensation of a synthesized diacid-diimide and 4,4′-(1,4-Phenylenediisopropylidene) bisaniline (PDBA). Diacide-diimide was synthesized by the condensation of an amino acid compound, (S)-(+)-Histidine hydrochloride monohydrate and 3,3′,4,4′-Benzophenone tetracarboxylic dianhydride (BTDA). On the other hand, a sulfonated polyimide (SPI) was also synthesized by the solution imidization of sulfonated, (4,4-diaminostilbene-2,2-disulfonic acid) (DSDSA) and non-sulfonated, 4,4′-(1,4-Phenylenediisopropylidene) bisaniline (PDBA) diamines in reaction with a six-membered naphthalene base dianhydride, 1,4,5,8-Naphthalenetetracarboxylic dianhydride (NTDA). A strong and flexible SPI membrane with good uniformity and proper thermal and mechanical properties was achieved. The SPI was then blended with different amounts of PAI and doped with phosphoric acid (PA), in order to investigate the blending influence of PAI in PA-doped blend membranes compared to the pure SPI membrane. It was found that a proper amount of PAI could effectively improve the water uptake, IEC and proton conductivity of the PA doped SPI/PAI membranes. Nevertheless the excess PAI negatively affected the membrane properties. The pure SPI with an IEC of 1.76 meq.g−1 showed a proton conductivity of 29.4 mS cm−1 at 120 °C, while PA doped SPI/PAI-10 % (w/w) as the most optimal PAI containing sample, with an IEC of 2.23, showed a proton conductivity of 69.7 mS cm−1 at 140 °C. The proton conductivity measurements were performed at 40 % relative humidity.
The primary objective of this study was to investigate the structure–property relationships in high performance polymers with high refractive indices and low birefringences. Hence, a series of novel poly(amide imide)s (PAIs) were synthesized from a thiazole-containing diimide-diacid monomer and various aromatic diamines. The influence of the pendant phenyl substituents on the optical properties of these PAIs was studied by comparison with the analogous polymers containing methyl groups. The PAIs exhibited excellent solubility and good thermal stability. The optical transmittances of the PAI films at 450 nm were higher than 75%. The combination of the thiazole units, thioether linkages, and pendant phenyl rings provided PAIs with high average refractive indices (nav) of 1.7361–1.7536 and low birefringences (Δn) of 0.0066–0.0097 at 632.8 nm.
AbstractA new thioether‐bridged diimide‐diacid (DIDA) monomer was synthesized from the condensation of 5,5′‐thiobis(2‐amino‐4‐methyl‐thiazole) (DA) and trimellitic anhydride at 1 : 2 molar ratio. A series of novel organic‐soluble poly(amide imide)s (PAIs) bearing flexible thioether linkages and heteroaromatic thiazole groups were synthesized from DIDA with various commercially available aromatic diamines (1–5) via a direct polycondensation method with triphenyl phosphite and pyridine. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.47–0.91 dL g–1. All of the polymers were amorphous in nature, showed good solubility and could be easily dissolved in amide‐type polar aprotic solvents (e.g., N‐methyl‐2‐pyrrolidone, dimethyl sulfoxide, and N,N‐dimethylacetamide), and even dissolved in less polar solvents (e.g., pyridine and tetrahydrofuran). They showed excellent thermal stability with glass transition temperatures between 233–269°C and 10% weight loss temperatures in excess of 480°C in nitrogen and 450°C in air atmosphere. The flexible structure endowed the PAI films with good optical transparency. The optical transmittances of the PAI films at 450 nm were higher than 80% for the thickness of approximately 10 μm. Moreover, the thiazole moieties and flexible thioether linkages in the molecular chains of the PAIs provided them with high refractive indices of 1.7329–1.7509 and low birefringences of 0.0065–0.0098. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
The functionalized conductive polymer precursor of the terthiophene derivative, 3′-(2-aminopyrimidyl)-2,2′:5′,2″-terthiophene (PATT) was firstly synthesized and confirmed with FT-IR, 1H NMR, 13C NMR, and mass spectroscopy. The electrochemical and electronic properties of polyPATT film are investigated and compared with that of poly(2,2′:5′,2″-terthiophene-3′-p-benzoic acid) (polyTTBA), which has an electron-accepting group. The cyclic voltammograms (CVs) recorded for electrochemically grown polyPATT reveal the redox peaks at +1.1/+0.96 V, and the conductivity increases monotonically as the applying potential goes to the positive direction (0.11 S cm−1 at +1.4 V). The spectroelectrochemical analysis of polyPATT reveals the absorption bands at 456, 825 and 643 nm corresponding to the π–π* transition, polaron, and bipolaron formations, respectively. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the polyPATT film bearing an electron donating group are to be 3.60 and 5.54 eV, respectively. The polyPATT film shows reversible multiple color transition within 0.6 s (from brownish-yellow (at 0.0 V) to blue (at +1.4 V)) when the potential switches between the reduced and oxidized states.
In this work, we synthesized amine functionalized graphene oxide called FGO-235 and FGO-178 by a chemical route. The prepared functionalized graphene oxide (FGOs) were characterized by different analytical methods including FT-IR, Raman spectroscopy, Thermal gravimetry (TG), Field-emission scanning electron microscopy (FE-SEM), X-Ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). To improve the electrochemical properties of the poly ortho aminophenol (POAP), we prepared FGO-235/POAP and FGO-178/POAP films through electro-polymerization of POAP in the presence of synthesized FGO-178 and FGO-235 with a porous structure, serving as the active electrode for electrochemical supercapacitor. With regards to electrochemical methods, galvanostatic charge–discharge experiments, cyclic voltammetry (CV), and electrochemical impedance spectroscopy were performed in order to investigate the performance of the system. The specific charges of 820 and 348 C g⁻¹ were obtained for FGO-235/POAP and FGO-178/POAP, respectively. This work introduced one of the most efficient materials for electrochemical redox capacitors which enjoyed easy synthesis, high active surface area, and stability in an aqueous electrolyte.
Three newly synthesized N‑benzoyl derivatives of isoleucine (3‑methyl 2‑[(4‑methylbenzoyl) amino] pentanoic acid (C-Me(2‑(benzoyl amino) 3‑methyl pentanoic acid (C-H) and 2‑[(4‑chlorobenzoyl) amino] 3‑methyl pentanoic acid (C-Cl) were synthesized via Schotten-Baumann method. Afterward, dealing with improving electrochemical properties of the poly ortho aminophenol (POAP), we fabricated POAP/C-Me, POAP/C-H and POAP/C-Cl films through electro-polymerization of POAP by employing of N‑benzoyl derivatives of isoleucine to consider as the active electrode for SCs. Based on the electronic wave function (DFT-method), the local intramolecular the electron density and its Laplacian, corresponding to atomic electronic kinetic energy, and molecular virial forces (in the molecular planes) of the molecular system is studied in this work calculated. Analysis of these results show that the atomic-scale electronic properties are generally depend on the bonding and electronic molecular structures and electron donating group on the N‑benzoyl derivatives has main important effect rather than electron withdrawing group. Based on electrochemical analyzing of POAP/C-Me, the specific capacitance, retention capacity and cycle stability as desirable factors in electrochemical SCs, exhibited more improved performances than electron withdrawing group in POAP/C-Cl film. According to electrochemical and quantum chemical evaluation, C-Me has improvement effect on electrochemical performance of POAP/C-Me electroactive film. This study reveals that POAP/C-Me with high fractal dimension, high specific capacitance and long cycle-life is suitable for application in energy storage materials.
In this study, Melamine functionalized graphene oxide (FGO-Melamine) was synthesized by chemical route. The prepared functionalized graphene oxide was characterized by different analytical techniques such as FT-IR, Raman spectroscopy, thermogravimetry coupled with mass spectrometry (TG-MS), X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS). To improve electrochemical properties of polyorthoaminophenol (POAP), the electropolymerized POAP/FGO-Melamine films, employed as an active electrode regarding electrochemical performance. In terms of electrochemical measurements, galvanostatic charge–discharge evaluation, EIS (electrochemical impedance spectroscopy) and CV (cyclic voltammetry) were employed for conducting an enquiry into supercapacitive performance of nanocomposite of POAP/FGO-Melamine. This graphene-based electrode showed a specific capacitance (SC) by 273 F g⁻¹ and high energy of 37.91 W kg⁻¹ at power density of 500 W kg⁻¹. The novel materials synthesized in the current work show higher efficiency compared to the carbon-based ones concerning redox reactions of capacitors consisting of good stability in the existence of aqueous electrolyte, large active surface area and ease synthesis method.
We present an efficient, highly selective and binder free non-enzymatic glucose sensor based on polyaniline@copper-nickel (PANI@CuNi) nanocomposite. PANI@CuNi nanocomposites with different loading ratio of nanoparticles (1: 025, 1: 0.33, 1: 05 and 1: 1) were prepared by mixing solution of PANI, synthesized through inverse emulsion polymerization method, and CuNi nanoparticles, synthesized through polyol process. The as prepared PANI@CuNi nanocomposites were coated on glassy carbon substrate without binder for non-enzymatic glucose sensing. A considerable increase in the active surface area of the electrode occurred after coating of this material. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry demonstrated that PANI@CuNi nanocomposite with 1: 0.5 ratio could be a good choice to be used as electrode material for non-enzymatic glucose sensing. The PANI@CuNi modified electrode exhibited high sensitivity (1030 μA mM−1 cm−2), good lower detection limit (0.2 μM) and a linear range of 5.6 mM (R2 = 0.992) with additional advantage of excellent selectivity, high stability and effective detection in real blood samples
We develop poly(aniline-co-anthranilic acid), PAAA, as a new electrically conductive and mechanically stable polymeric binder material for silicon anodes. In contrast to the electrically conductive but poorly Si-adhering polyaniline, the PAAA copolymer, which is designed to consist of anthranilic acid units as well as aniline units, is found to adhere to Si strongly in addition to being electrically conductive, and is hence able to be used alone for the production of the silicon anode. Various PAAA copolymers having different relative amounts of anthranilic acid are prepared to investigate the effect of anthranilic acid on the electrical and physical properties of the corresponding electrodes. The copolymer whose composition is 50% aniline and 50% anthranilic acid displays the best cell performance due to the most balanced electrical conductivity and physical properties, with a specific capacity of 1946 mAh g⁻¹ at the 50th cycle, which represents a retention of 81.6% of the initial capacity, on a high mass loading electrode of 1.5 mg cm⁻².
We report herein the controlled synthetic strategy for Prussian blue nanoparticles (PBNPs) formation justifying the role of functional alkoxysilanes, [2-(3,4-Epoxycyclohexyl)ethyl]trimethoxysilane (EETMSi) in the presence of tetrahydrofuran hydroperoxide (THF-HPO) with following major findings: (i) significant change in nanogeometry from 40 to 8 nm by addition of EETMSi and (ii) allowed fabrication of PBNPs encapsulated silica-alginate beads. As made nanoparticles were characterized by UV–Vis spectroscopy, TEM, FT-IR, and SEM. Size dependent electrochemical behavior of three different PBNPs i.e. PBNPs-1 (26 nm), PBNPs-2 (17 nm) and PBNPs-3 (8 nm) was recorded based on cyclic voltammetry. Apart from unprecedented size-dependent properties, as made PBNPs-3 display excellent peroxidase mimetic activity with Km value to the order of ∼0.9 mM. In addition, EETMSi also allows to cast Prussian blue film and simultaneously enable the formation of silica-alginate beads with controlled pores size perfectly suitable for encapsulating these nanoparticles which allocate selective electrochemical oxidation of Pyrogallol (Py) at 0.3 V vs. Ag/AgCl.
Currently, most metal oxides- or hydroxides-based and non-enzymatic sensors require a high alkali concentration in the working environment. Here, we designed a novel non-enzymatic sensor based on a 3D nanostructured Co(OH)2/rGO film to address this issue. The architecture of the hybrid film was in-situ constructed by the dense assembly of 200 nm flower-like Co(OH)2 crystals bridged by rGO nanosheets. This structure possessed an extremely large specific surface area and an excellent conductivity which were beneficial for adsorbing OH– to produce oxidative CoOOH or CoO2, even in a low alkaline condition. This material was able to mimic the functionality of glucose oxidase to oxidize glucose to gluconolactone and exhibited a good sensitivity at a wide alkaline range from 5 × 10⁻³ to 1 mol L⁻¹ NaOH solution. Moreover, this sensor showed a wide linear range, excellent selectivity, reproducibility and stability for real blood analysis.
the room temperature electrochemically fabricated POAP/[Cu2(2-mpinh)2Cl2(H2O)]n electrode was introduced as a highly effective candidate for supercapacitor application. Not only surface analyses but also electrochemical techniques, including cyclic voltammetry, galvanostatic chargedischarge experiments along with electrochemical impedance spectroscopy, were conducted to characterize the prepared [Cu2(2-mpinh)2Cl2(H2O)]n composite films and examine the performance of the system, respectively. Novel nanocomposite materials were presented for electrochemical redox capacitors possessing the merits of high active surface area and high stability in an aqueous electrolyte, as well as ease of fabrication.
A traditional approach is conducted for the preparation of polyaniline/graphene oxide (PANI/GO) nanostructures, where aniline monomer followed by ammonium persulfate (APS) were added to an acidic solution of graphene oxide (GO). Herein, we investigate a condition in which firstly GO is dispersed in acidic media containing APS. The aniline monomer is then added in order to the in-situ polymerization of aniline. An investigation is also carried out on the effect of the acid type including sulfuric acid (H2SO4), hydrogen chloride (HCl), perchloric acid (HClO4), and p-toluenesulfonic acid (PTSA) on the morphology and electrochemical behavior of resultant PANI/GO nanostructures. The characterizations reveal well-defined nanoarrays for PANI/GO-H2SO4 electrode with the highest porosity and specific surface area. This electrode exhibits a highest current density in cyclic voltammetry studies and the most specific capacitance (727 F g-1) in charge/discharge studies among other as-prepared electrodes. Utilizing this PANI/GO-H2SO4 nanocomposite as the electrodes in a symmetric configuration resulted in the development of devices with remarkable performance including a maximum energy density of 40 Wh kg-1 and a power density up to 15.3 kW kg-1 with an excellent cycle life (only 4.3% loss after 5000 cycles).
To date, significant effort has been focused on the active materials in the supercapacitor electrodes. However, very little has been done for the binder materials. Insulating fluorinated polymer binders, which are used for fabrication of carbon electrodes in supercapacitors, reduce electrode conductivity, capacitance, and rate performance. Here we propose to use reduced graphene oxide (rGO) as a multi-functional conductive binder as a general strategy for manufacturing freestanding, flexible, high-performance supercapacitor electrodes from various micron-sized porous carbons. The two-dimensional structure, high specific surface area and effective electronic conductivity of rGO enable us to eliminate the addition of insulating binder, conductive additive, and current collector. The synergetic effect of rGO with carbon materials produces a 3D conductive network and enlarges the electrode/electrolyte interface, enhancing electrode capacitance and rate performance in both aqueous and non-aqueous electrolytes. Using rGO as a binder, we prepared various high-performance and flexible electrodes from activated carbon powders, fibers and spheres, in which both the composition and thickness are controllable. This demonstrates that rGO can be used as a binder for porous carbons with different morphologies. As this strategy is environmentally friendly and easy to scale-up, we believe it is a promising method for fabrication of all-carbon and composite electrodes.
Asymmetric supercapacitors are one of the promising next-generation electrochemical energy storage devices. However, the necessity to distinguish the polarity of asymmetric supercapacitors makes it more like rechargeable batteries and affects the convenience of practical applications. We herein report a novel flexible asymmetric supercapacitor (FASC) that can be charged without distinguishing the electrode polarity based on CVD-grown nickel [email protected] nanotube ([email protected]) network films. The FASC is assembled by using the binder-free [email protected] as both the negative and positive electrodes but aqueous alkaline solution as the electrolyte. In such a design, one electrode side is involved with the Faradaic redox reactions between nickel nanoparticles and OH⁻, while the other side works via electric double layer charge accumulation at the interface of CNTs/electrolyte, enabling the device with an asymmetric feature and a high voltage of 1.8 V. Exactly because of the above, the FASC demonstrates almost the same charge/discharge profiles, stable cycling and comparable efficiency for powering small electronics even with frequently alternating the charging direction. With the integration of hydrogel electrolyte of PVA-KOH, our flexible quasi-solid-state FASC device delivers high volumetric energy density of 1.39 mWh cm⁻³ and power density of 440 mW cm⁻³, as well as excellent cycleability up to 10,000 times (100% capacitance retention). The volumetric performance is even much better than previous reported FASC devices that were designed with complicated electrode architectures. Our work presents a pioneering strategy for developing non-polarity asymmetric electrochemical energy storage systems.
In the present work, zeolitic imidazolate framework (ZIF-67) was synthesized via chemical routes. For improving the electrochemical performance of the conductive polymer, POAP/ /ZIF-67 composite films were fabricated by POAP electropolymerization in the presence of ZIF-67 as active electrodes for electrochemical supercapacitors. The structural and the valance states of the prepared samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Different electrochemical methods, including galvanostatic charge discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy, have been applied to study the system performance. The supercapacitive behavior of the composite film was attributed to the (i) high active surface area of the composite, the (ii) charge transfer along the polymer chain due to the conjugation form of the polymer, and finally, the (iii) synergism effect between the conductive polymer and ZIF-67.
In present work, for improving the electrochemical performance of conductive polymer, POAP/ 1-octadecyl-3-methylimidazolium Bromide ([OMD]Br) composite films have been fabricated by POAP electropolymerization in the presence of [OMD]Br as active electrodes for electrochemical supercapacitors. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance. Analyses of DFT results show that the atomic-scale electronic properties are generally depend on the bonding and electronic molecular structures (and thus their variation with the external bias in real nano-electrochemical circuits). The supercapacity behavior of the composite film was attributed to the i) high active surface area of the composite, ii) charge transfer along the polymer chain due to the conjugation form of the polymer and finally iii) synergism effect between conductive polymer and [OMD]Br.
This study demonstrates a method for improving supercapacitive performance of electrochemically synthesized conductive polymer. In this regards, 1-Butyl – 3- methyl imidazolium hexafluorophosphate (BI) as a new high efficient ionic liquid was synthesized using chemical approach and then fabricated POAP/ BI films by electro- polymerization of POAP in the presence of BI to serve as the active electrode for electrochemical supercapacitor. Theoretical study (AIM) and electrochemical analysis have been used for characterization of ionic liquid and POAP/ BI composite film. Different electrochemical methods including galvanostatic charge–discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new most efficient materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte.
Herein, we report for the first time a facile and cost-efficient synthesis of metal oxide nanostructures comprised of nanorods type without the use of any additive. Nd(OH)3 and Nd2O3 nanorods were obtained by ultrasound wave assisted pulse electrochemical deposition in a Nd(NO3)3·6H2O nitrate bath. In addition, the interconnected nanorods were mesoporous leading to large electrochemical active sites for the redox reaction and fast ion transport within the Nd2O3 nanorods. Furthermore, for improving the electrochemical performance of conductive polymer, hybrid POAP/Nd2O3 films have then been fabricated by POAP electropolymerization in the presence of Nd2O3 nanorods as active electrodes for electrochemical supercapacitors. Surface and electrochemical analyses have been used for characterization of Nd2O3 and POAP/Nd2O3 composite films. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance. Prepared composite film exhibited a significantly high specific capacity, high rate capability and excellent cycling stability. Importantly, electrochemical investigation show that POAP/Nd2O3 nanorods composite material has better properties than POAP without Nd2O3 nanorods, suggesting it can be used as supercapacitor electrode material with excellent specific capacitance (379Fg(-1)) which indicates this material is a promising electrode material for energy storage applications in high-performance pseudocapacitors.
Pulsed base (OH-) electrogeneration was applied to the cathodic electrodeposition of manganese oxide from chloride bath for the first time, and Mn3O4 nanorods were prepared. The deposition experiments were performed under a pulse current mode in a typical on-times and off-times (ton=10 ms and toff=50 ms) at a peak current density of 1 mA cm−2 (Ia= 1 mA cm−2). The structural characterizations with XRD and FTIR revealed that the prepared sample is composed of tetragonal crystal phase of Mn3O4. Morphological evaluations by SEM further proved that the prepared Mn3O4 is made up of large scale and vertically aligned one-dimensional (1D) nanorods with uniform shapes and an average diameter of 50 nm. The electrochemical measurements through cyclic voltammetry (CV) and charge-discharge techniques revealed that the prepared Mn3O4 nanorods have an excellent capacitive behavior, with the specific capacitances as high as321, 292, 264, 222, 187 and 132 F g─1 at the scan rates of 2, 5, 10, 25, 50 and 100 mV s−1, respectively. The excellent long-term cycling stabilities of 91.7%, 83.4%, and 75.7% were also observed after 1000 charge–discharge cycles at the current densities of 1, 5 and 10 A g−1, respectively.
Carbon aerogels and their precursory polymer aerogels are an important class of porous materials, because they have a unique three-dimensional interconnected nanonetwork structure that can minimize diffusive resistance to mass transport. However, production of conventional aerogels in a monolithic form remains problematic, because of risk of explosive polymerization, tedious supercritical/freeze drying steps, extra ball milling, and difficulty in controlling micro/nanostructures. Here we show that novel powdery carbon aerogels and their polymer aerogel precursors have been developed by utilizing shape-persistent nanoparticles as building blocks, followed by hypercrosslinking for forming a well-defined 3D interconnected nanonetwork with numerous interstitial nanopores and intraparticle micropores. The resulting aerogels are in a microscale powdery form. The preparation route is much more feasible for scaling up, due to avoidance of explosive polymerization and facile drying at ambient pressure. By simple carbonization, powdery carbon aerogels can be obtained with a high surface area of 2052 m² g⁻¹. Benefiting from structural advantages, the aerogels demonstrate excellent electrochemical performances in supercapacitors and lithium-sulfur batteries.
We fabricated unique structured electrodes composed of three-dimensional porous active carbon fibers (ACFs) coated with polyaniline and few-layer graphene (PANI/FLG-coated ACFs), which demonstrated excellent capacity for application in supercapacitors. Ni networks served as the template for graphene grown by annealing the electrodeposited Ni clusters on the surface of ACFs. After chemical vapor deposition, FLG was synthesized on the Ni surface which was subsequently coated with PANI serving as capacitive materials and supporting layers for FLG in the construction of shell structures during Ni etching. The surface combined a pultruded structure and cavity network formed with the PANI/FLG coatings, where the holes on the cavity increased the electroactive surface area and facilitated penetration of the electrolyte into the cavity networks, as a result the capacity was enhanced. In this study, an average specific capacitance of 400.16 F g⁻¹ and an energy density of 61.27 W h kg⁻¹ at a charging current of 0.1 A g⁻¹ over the PANI/FLG-coated ACFs electrodes were achieved.
The ultrathin two-dimensional structure and unique properties of graphene make it highly attractive for high-performance asymmetric supercapacitors (ASCs), which are generally constructed by two different materials as positive electrode and negative electrode, respectively, in an asymmetric configuration. Here, a deep insight into the recent advances of graphene-based materials for high-voltage and high-energy asymmetric supercapacitors (ASCs) is presented. First, the critical aspects that directly affect the performance of ASCs and how they have been tackled in terms of the assembly principle of ASCs and standard methods of accurate performance evaluation are discussed. Second, the major categories and the state-of-the-art positive and negative electrode materials of ASCs are described. Third, the latest advances of different graphene-based nano-architectures, such as reduced graphene oxide, porous graphene, graphene quantum dots, graphene nanoribbons, graphene fibers, graphene films, graphene aerogels, graphene foams, and various hybrids of graphene/carbon nanotubes, graphene/metal oxides and graphene/conducting polymers, for ASCs are summarized. Fourth, major performance parameters, including high voltage, high capacitance, high power and high energy devices, as well as new device geometry of planar and all-solid-state devices, are described in details, highlighting the uniqueness and superiority of graphene for hybrid energy storage. Fifth, The elaborated screening of graphene-based materials with controllable morphologies, two-dimensional and three-dimensional well-defined nanostructures, and tailored compositions, architectures of the electrode, selection of electrolytes, and optimized integrity of different device components are overviewed. Finally, future perspectives and challenges of graphene-based ASCs are discussed.
In this paper, a simple and rapid electrochemical method has been carried out to prepare Holmium oxide (Ho2O3) nanoparticles and composite film to serve as the active materialinan energy storage electrode. Hybrid films of poly ortho aminophenol (POAP) and Ho2O3 were obtained through potentiodynamic deposition from solutions of ortho aminophenol and Ho2O3. The hybrid films demonstrated characteristic redox behaviors of POAP in acidic aqueous solution. Structural and morphological characterizations of Ho2O3 and composite film were carried out using powder X-ray diffraction and field emission scanning electron microscopy. Their electrochemical properties were also investigated using cyclic voltammetry, galvanostatic charge?discharge and electrochemical impedance spectroscopy. Electrosynthesized composite had excellent properties in the capacitance and a columbic efficiency of 94%. This work introduces new nanocomposite materials for energy storage electrodes with advantages including ease of synthesis, high active surface area and stability in an aqueous electrolyte.
Metal oxides have attracted renewed interest in applications as energy storage and conversion devices. Here, a new design is reported to acquire an asymmetric supercapacitor assembled by all free-standing metal oxides. The positive electrode is made of 3D NiO open porous nanoribbons network on nickel foam and the negative electrode is composed of SnO2/MnO2 nanoflakes grown on carbon cloth (CC) substrate. The combination of two metal oxide electrodes which replaced the traditional group of carbon materials together with metal oxide has achieved a higher energy densities. The self-supported 3D NiO nanoribbons network demonstrates a high specific capacitance and better cycle performance without obvious mechanical deformation despite of undergoing harsh bulk redox reactions. The SnO2/MnO2 nanoflakes as the pseudocapacitive electrode exhibit a wide range of voltage window (-1V~1V), which is conducive to electrochemical energy storage. The (CC/SnO2/MnO2)(-)//(NiO/Ni foam)(+) asymmetric supercapacitor device delivers an energy density of 64.4 Wh kg-1 (at a power density of 250 W kg-1) and two devices in series are applied to light up 24 red LEDs for about 60s. The outstanding electrochemical properties of the device hold great promise for long-life, high-energy and high-power energy storage/conversion applications.
In this work, we presented facile route for fabrication of poly ortho aminophenol (POAP) POAP and POAP/ZnO nanocomposite on the surface of the working electrode. The fractal dimension of nanocomposite films in the presence of counter ions was investigated. Surface morphology of the composite film was studied by surface microscopy techniques (SEM). The presence of ZnO in the films was confirmed by EDS analysis. The results indicate that a strong interaction exist at the interface of POAP and nano-ZnO. Different electrochemical methods including galvanostatic charge discharge experiments and cyclic voltammetry have been applied to study the system performance. This work introduces new nanocomposite materials for electrochemical redox capacitors with such advantages as the ease of synthesis, high active surface area and stability in an aqueous electrolyte. Furthermore, comparison with a Ni-POAP the Ni-POAP/ZnO electrode shows a better catalytic performance for the electrocatalytic oxidation of methanol in alkaline solution. It is observed that the in the presence of ZnO nanoparticles current density of electro-oxidation of methanol is almost constant in 400 cycles due to the stability of electrocatalyst in this cycle number and indicating that methanol reacted with the surface and no poisoning effect on the surface was observed.
An effective approach for increasing the life cycle of pure p-type conductive polymers is combining conventional conductive polymers and nanomaterials to fabricate hybrid electrodes. In this paper, Gadolinium oxide (Gd2O3) has first been synthesized using pulse electrochemical approach. Hybrid POAP/Gd2O3 films have then been fabricated by POAP electropolymerization in the presence of Gd2O3 nanoparticles as active electrodes for electrochemical supercapacitors. Surface and electrochemical analyses have been used for characterization of Gd2O3 and POAP/Gd2O3 composite films. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance. Specific capacitance, specific energy and specific power of the composite film are calculated 300 F·g⁻¹, 41.66 W h·kg⁻¹ and 833.22 W·kg⁻¹ respectively. This work introduces new nanocomposite materials for electrochemical redox capacitors with such advantages as the ease of synthesis, high active surface area and stability in an aqueous electrolyte.
A new class of highly conductive and durable polymer electrolyte membranes have been developed for fuel cell applications under elevated temperature and/or low relative humidity (RH). Highly phosphonated and fully aromatic diamine monomer was prepared via three-step high-yielding procedure from previously synthesized phosphonated bisphenol: halogen displacement of 1-fluoro-4-nitrobenzene, reducing of nitro groups, and hydrolysis of phosphonate ester groups. A series of phosphonated copolyimide ionomers with ion exchange capacity (IEC) of 2.4-4.6 mequiv.g-1 were obtained by a typical polycondensation reaction followed by solution casting to form transparent and flexible membranes. Proton conductivity of the phosphonated membranes was comparable to that of the commercial perfluorinated ionomer at 100% RH. Typically, the conductivity value of up to 125 mS cm-1 was obtained for the membrane with IEC of 3.5 mequiv.g-1 at 100 °C. However, by reducing the relative humidity the merits of phosphonated polyimides became more evidence and their dry state conductivity was 1-3 order of magnitudes higher than Nafion 115 and substantially higher than the values reported for phosphonated membranes. Thermogravimetric analysis and long-term proton conductivity study of phosphonated copolyimides at high temperatures (up to 160 °C) and low humidity confirmed small amount of undesired self-condensation of phosphonic acid groups compared with other phosphonated membranes.
In this manuscript we present the interfacial characterization of poly(pyrrole) films doped with dodecylbenzenesulphonate anions (DBS) electrosynthesized under the influence of ultrasonic radiation. The modified electrodes were studied by means of scanning electron microscopy and electrochemical experiments. It was shown that the ultrasonic radiation changes the morphology of the deposits producing smoother films, with distinct voltammetric behavior. A detailed study employing the electrochemical impedance spectroscopy was done where important features such as the charge-transfer resistance, intercalated charge distribution and double-layer capacitance were discussed. The results showed herein are of great importance on the development and characterization of electroactive surfaces where modified electrodes can be easily obtained by using the ultrasonic radiation and the studies of electrochemical based devices such as sensors, biosensors and supercapacitors can be boosted.
In this paper, firstly Al5Y3O12 (YAG) has been synthesized without any impurities using pulse electrochemical deposition technology and then fabricated hybrid POAP/YAG films by electro-polymerization of POAP in the presence of YAG nanoparticles to serve as the active electrode for the electrochemical supercapacitor. Electrosynthesized YAG nanoparticles and POAP/YAG nanocomposites have been characterised by common surface analysis techniques such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. Different electrochemical methods including galvanostatic charge–discharge (CD) experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte to that of commonly used ruthenium based perovskites.
A new approach has been proposed for the preparation of nanostructured α-MnO2. The method is based on the galvanostatic cathodic electrodeposition of the product from a nitrate bath under a direct current mode at a current density of 0.1 mA cm−2. The intermediate product deposited in this stage is next thermally treated at 300 °C for 3 h. To evaluate the properties of the final product, it was characterized by XRD and FTIR so as to gain information on its phase composition (which was found to be mainly α-MnO2) and SEM to gain information on its morphology (which was found to be nanospheres with secondary porous wall-like nanostructures). Additional electrochemical experiments on the product through cyclic voltammetry and charge–discharge tests revealed it to be capable of delivering high specific capacitance of 280 F g−1, further its outstandingly long-term cycling stability which was only diminished to 95.4 % of the initial value after 1000 discharge cycles.
A coherent polyaniline (PANI)/graphene oxides (GOs)/multi-walled carbon nanotubes (MWCNTs) composite was prepared by in-situ solution polymerization as a positive electrode of supercapacitors. The orderly growth of PANI nano-dots on GOs led to the formation of the nano-ravines that can enhance ions diffusion efficiency. MWCNTs surrounded by PANI connected all components, and thus the conductivity with the increasing electron transfer rate was improved. The results showed that the electrode exhibited the outstanding electrochemical performances with the specific capacitance up to 696 F g−1 at 20 mV s−1. The KOH-activated GOs/MWCNTs were used as a negative electrode to assemble an asymmetric supercapacitor (ASC). The ASC possessed an extended working potential (1.6 V), a good rate capability (58% capacitance retention even after the current density being increased by 10 times), an excellent cycling stability (89% capacitance retention after 3000 cycles), and a decent average energy and power density (69 W h/kg and 6.4 kW/kg).
A simple and convenient one-step hydrothermal process for synthesizing nitrogen-doped graphene/p-aminophenol composite by using ethylenediamine, p-aminophenol, and graphene oxide is described. The p-aminophenol does not only act as a spacer to prevent the graphene sheets from aggregating and restacking during the hydrothermal process but also enhances the contribution of pseudocapacitance, which further improves the performance of the electrode materials. The field emission scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical workstation are used to characterize the materials. The as-produced composite material shows superior specific capacitance of 365.7 F g−1 at a scan rate of 10 mV s−1 and excellent electrochemical cycle stability.
An attempt has been made to evaluate comparatively the behavior of 2-methylaniline (2MA) and 3-methylaniline (3MA) during electrochemical homo- and copolymerization. As comonomer in the copolymerization bath with 2MA and 3MA 1,2-diaminobenzene (1,2-DAB), an aromatic diamine, was selected. Cyclic voltammetry was used both for the electrochemical synthesis and characterization of the homopolymers and copolymers on a gold electrode. In the copolymerization bath mixed solutions of the monomers having different concentrations of 1,2-DAB and a constant concentration of 2MA or 3MA were used. The voltammograms exhibit different behavior for different concentration ratios of the monomer in the feed. The homopolymers poly(2-methylaniline) (P2MA) and poly(3-methylaniline) (P3MA) show similar electrochemical properties. However, differences were observed in the properties between the copolymers of 2MA and 3MA with 1,2-DAB that could be due to the variation in the monomer units and orientation along the copolymer chains. The copolymerization of 1,2-DAB seems to be more facilitated when instead of 3MA, 2MA is present as comonomers. The effect of scan rate and pH on the electrochemical activity was studied. The copolymers are surface confined, electroactive and show good electrochemical activity even at pH = 8.0 and pH = 9.0 in case of poly(1,2-DAB-co-3MA) and poly(1,2-DAB-co-2MA), respectively. In situ conductivity measurements further support the differences in the structure of the copolymers of 1,2-DAB with 2MA and 3MA.
The poly(methylene blue) (PMB) modified glassy carbon electrode (GCE) exhibiting different electrochemical behavior was prepared via two methods, respectively. The PMB polymer, derived from the two-step electropolymerization, suffered structure conversion between Poly(leuco-MB) and Poly(MB) during cyclic voltammetric measurement and exhibited electrocatalytic activity for reduction of dissolved oxygen (DO). The monodispersed hollow methylene blue doped SiO2 nanoparticles were synthesized in the W/O microemulsion. A new material, PMB doped SiO2 nanocomposites, presenting monolayer sheets with crosslinked cage structure, were electrochemically polymerized on GCE surface. Compared with PMB film, the nanocomposite material provided a significantly improved sensitivity for reduction of DO and an excellent ability to resist interference from macromolecule contaminants. The detection of DO was performed using the nanocomposite material modified electrode. The calibration curve was linear over a DO concentration range of 0.112–5.78mgL−1 with a correlation coefficient of 0.998 and a detection limit (3σ) of 0.037mgL−1.
An overview is given on electrochemically prepared intrinsically conducting copolymers, their preparation, their properties, potential applications and significant differences from the respective homopolymers. Particular attention is paid to verification of the formation of true copolymers and their characteristic features in comparison to mixtures of homopolymers.
Two kinds of functionalized graphene sheets were produced by thermal exfoliation of graphite oxide. The first kind of functionalized graphene sheets was obtained by thermal exfoliation of graphite oxide at low temperature in air. The second kind was prepared by carbonization of the first kind of functionalized graphene sheets at higher temperature in N2. Scanning electron microscopy images show that both two kinds of samples possess nanoporous structures. The results of N2 adsorption–desorption analysis indicate that both of two kinds of samples have high BET surface areas. Moreover, the second kind of functionalized graphene sheets has a relatively higher BET surface area. The results of electrochemical tests is as follows: the specific capacitance values of the first kind of functionalized graphene sheets in aqueous KOH electrolyte are about 230Fg−1; the specific capacitance values of the second kind of functionalized graphene sheets with higher BET surface areas are only about 100Fg−1; however, compared with the first kind of functionalized graphene sheets, the second kind has a higher capacitance retention at large current density because of its good conductive behaviors; furthermore, in non-aqueous EC/DEC electrolyte, the specific capacitance values of the first kind sample and the second kind sample are about 73Fg−1 and 36Fg−1, respectively.
UV–vis absorption spectra and cyclic voltammograms of a selection of substituted thiophenes and their oligomers carrying trifluoracetyl acetone functional groups have been obtained. A comparison with calculated values of HOMO–LUMO energies (the former corresponding to the ionization potentials Ei) shows strong correlations between calculated and experimentally obtained data; they are in close agreement with estimates in terms of electron-donating and -withdrawing effects from an empirical point of view.
Electropolymerization of aniline on poly(o-aminophenol)(POAP)-coated gold and indium-doped tin oxide (ITO)-coated glass electrodes yields polyaniline(PANI)/POAP two-layer composite films, exhibiting reversible redox functions in aqueous acidic solution. The PANI deposition on the POAP-coated electrodes was monitored by cyclic voltammetry (CV) and in situ UV–vis spectroelectrochemistry. CV results show that PANI/POAP composite films exhibit better stability as compared to PANI films during potential cycling in aqueous acidic solutions. Characteristic UV–vis and Raman features of the composite films have been identified and their dependencies on the electrode potential are discussed. They were significantly different from the corresponding spectral characteristics of PANI and POAP films alone.