Electropolymerization and energy storage of poly[Ni(salphen)]/MWCNT composite materials for supercapacitors

Ni(salphen), a Schiff base ligand compound, was synthesized and electropolymerized on multiwalled carbon nanotube (MWCNT) electrodes in an acetonitrile solution via the pulse potentiostatic method and then applied as a supercapacitor electrode material. The polymerization mode was investigated through methyl replacement in the para‐position of phenyl rings in the Ni(salphen) monomer, and it was found that the Ni(salphen) monomers would polymerize by the generation of C? C bonds between the phenyl rings in the para‐position of the phenol moieties. The optimum condition for polymerization was evaluated, and when the polymerization time was 8 min, poly[Ni(salphen)] exhibited a specific capacitance up to 200 F g^?1 at a current density of 0.1 mA cm^?2, and the capacitance remains at 164 F g^?1 at 20 mA cm^?2. The energy density of the poly[Ni(salphen)] electrode reached 40 Wh kg^?1 at 0.1 mA cm^?2, about eight times greater than for a pure MWCNT electrode. Electrochemical performances were investigated, and the composites showed good redox property and ion transfer capability. This work showed that Ni(salphen) may be an attractive material in supercapacitors© 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44464.     

Polyaniline with high crystallinity degree: Synthesis,structure, and electrochemical properties

Polyaniline (PANI) with high crystallinity degree was facilely synthesized on the surface of stainless steel net by galvanostatic method. The effect of polymerization current density on the characteristics of morphology and structure had been investigated by field emission scanning electron microscopy (FE‐SEM), Fourier transforms infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffraction (XRD). FE‐SEM observations disclosed that PANI was deposited as nanofibers and their diameters decreased with the polymerization current density. FTIR studies revealed that degree of oxidation increased in order PANI‐2 < PANI‐6 < PANI‐10. XPS measurements displayed that PANI polymerized at 6 mA cm^?2 (PANI‐6) exhibited much higher doping level of 77.8%, which favored the conductivity. XRD analysis discovered that the obtained PANI showed high crystallinity degree in which PANI‐6 possessed highest crystallinity degree (X_cr) up to 67%. Electrochemical performances of PANI as electrode materials were studied via cyclic voltammetry. The results presented that PANI‐6 possessed greater discharge capacity and better reversibility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40827.     

Interfacial synthesis of polypyrrole/graphene composites and investigation of their optical,electrical and electrochemical properties

We report the development of a novel route for the synthesis of polypyrrole/graphene (PPy/GR) composites by liquid ? liquid interfacial polymerization, where GR and the initiator were dispersed in the aqueous phase and the monomer was dissolved in the organic phase. The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, electrochemical and electrical conductivity measurements. Structural analysis reveals a uniform dispersion of GR sheets in the PPy matrix. The composites showed noticeable improvement in thermal stability and electrical conductivity (8.45 S cm^?1) and excellent electrochemical reversibility in comparison with pure PPy. A specific capacitance of 260 F g^?1 at a current density of 100 mA g^?1 was achieved for the composite during the charge–discharge process. © 2013 Society of Chemical Industry     

Simultaneous Oxidation and Doping of Aniline to Polyaniline by Oxidative Template: Electrochemical Performance in Supercapacitor

Polyaniline salts containing sulfuric acid and cetyltrimethylammonium sulfate dopants were prepared by aqueous (PANI-Aq), emulsion (PANI-Em), and interfacial (PANI-In) polymerization pathways using cetyltrimethylammonium peroxodisulfate as an oxidative template. Formation of polyaniline was confirmed from infrared and X-ray diffraction spectral results. Value of conductivity (15 S cm^?1) of the polyaniline salt prepared by emulsion polymerization pathway was higher with that of the conventional polyaniline salt. PANI-Aq, PANI-Em, and PANI-In showed layered, flower petals, and nanorod and flower petals morphologies, respectively. These polyaniline salts were used as electrode in supercapacitor. Specific capacitance of PANI-Em, PANI-Aq, and PANI-In were 520, 484, and 474 F g^?1, which were higher than the conventional PANI-H₂SO₄ salt (390). Energy density was 26, 24.2, and 23.6 Wh kg^?1, respectively at a power density of 120 W kg^?1. After 3000 charge-discharge cycles, retention in the specific capacitance values of polyaniline salts was 86% (PANI-Em), 85.4% (PANI-Aq) and 76.1% (PANI-In).     

Polymer coatings by electropolymerization of some vinyl monomers

Electroinitiated polymerization coatings are uniform, thin, tightly adherent, conformal, and economical to produce. This article describes use of a novel (for electropolymerization) persulfate initiator to rapidly polymerize a moderate T_g crosslinked acrylic coating. Polymer coatings derived from the monomers acrylamide, acrylonitrile, and N,N′-methylenebisacrylamide were synthesized on an aluminum cathode by persulfate electroinitiated polymerization at room temperature. The crosslinked polymer was brittle (T_g = 239°C) but thermally stable (degradation temperature = 310°C). The coatings were spongy and contained some small cracks when polymerized at low current density (0.1 mA/cm²). However, thicker coatings with fewer cracks were obtained at higher current densities. Persulfate was found to be an effective initiator for polymerization in this system, and the initiation mechanism was confirmed to be free radical. In general, it appears possible to produce thin, uniform coatings on aluminum by this route. © 1995 John Wiley & Sons, Inc.     

Aqueous,interfacial, and electrochemical polymerization pathways of aniline with thiophene: Nano size materials for supercapacitor

Aniline was mixed with thiophene and oxidized by ammonium persulfate in the presence of sulfuric acid via an aqueous polymerization pathway (PAT‐AP). Aqueous polymerization was also carried by sodium lauryl sulfate surfactant, and also by interfacial and electrochemical polymerization pathways. Polymers prepared were characterized by physical, spectral, and electrochemical methods. Nanofibers (30–60 nm diameter) was obtained in the case of aqueous polymerization pathway, whereas interfacial (40–60 nm) and electrochemical polymerization pathways show particulate (500–600 nm) morphology. Polymer samples were used as electrode materials in supercapacitor. Among the four different pathways, PAT‐AP nanofibers show higher capacitance of 614 F g^?1 at 1 mV s^?1. The values of specific capacitance, energy, and power densities of PAT‐AP were found to be 400 F g^?1, 20 W h kg^?1 and 1200 W kg^?1, respectively, at a current density of 2 A g^?1. The retention capacitance is 78% after completion of 1000 cycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42013.     

Multifunctional polyaniline–tin oxide (PANI–SnO2) nanocomposite: Synthesis,electrochemical, and field emission investigations

Synthesis of PANI–SnO₂ nanocomposite has been performed using a simple two step chemical oxidative polymerization route. The structural, morphological and chemical properties of the as‐synthesized PANI–SnO₂ nanocomposite have been revealed by various characterization techniques such as SEM, TEM, XRD, FTIR, and XPS. Interestingly the as‐synthesized PANI–SnO₂ nanocomposite exhibits supercapacitance value of 721 F g^?1 with energy density 64 Wh kg^?1, which is noticed to be higher than that of pristine SnO₂ and PANI nanostructures. Furthermore, the galvanostatic charge–discharge characteristics revealed pseudocapacitive nature of the PANI–SnO₂ nanocomposite. The estimated values of charge transfer resistance and series resistance estimated from the Nyquist plot are found to be lower. Along with the supercapacitive nature, PANI–SnO₂ nanocomposite showed promising field emission behavior. The threshold field, required to draw emission current density of 1 μA/cm², is observed to be 0.90 V/μm and emission current density of 1.2 mA/cm² has been drawn at applied field of ～2.6 V/μm. The emission current stability investigated at preset values of 0.02 and 0.1 mA/cm² is observed to be fairly stable over duration of more than 3 h. The enhanced supercapacitance values, as well as, the promising field emission characteristics are attributed to the synergic effect of SnO₂ nanoparticles and PANI nanotubes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41401.     

Hydrothermally synthesised nickel oxide nanostructures on nickel foam and nickel foil for supercapacitor application

Nickle-based oxides exhibit seamless redox activity and show undisputed parameter optimization flexibility, which makes them a candidate of choice for various scientific analysis and multipurpose execution. The communique addresses the domain of energy storage of hydrothermally fabricated nickel oxide nanostructures by analysing the capacitive behaviour of the sample. The crystal geometry, chemical composition and bonding state of the material were carried out through XRD and XPS analysis, respectively. Electron microscopy showed systematically aligned nano-needles, which in aggregate represent an urchin. A comparative study of specific capacitance (Cs) at a scan rate of 1 mVs^?1 showed an enhanced Cs of nickel oxide embedded Ni-foam (1125 Fg^-1) against nickel oxide deposited Ni-foil (454 Fg^-1). At a current density of 8 mAcm ^?2, the nickel oxide based Ni-foam electrode exhibited an energy density of 23 Whkg^?1 and a power density of 259 Wkg^-1 which makes it instrumental in electrochemical devices. The Ni-foam electrode also showed less ‘cycle fatigue’ as its charge/discharge stability dipped by just 12% even after 5000 cycles. The novel supercapacitor electrode developed in this study exhibits excellent specific capacitance, high stability, high power density, and low impedance, demonstrating its promising practical functionality.     

Experimental investigation of Co and Fe-Doped CuO nanostructured electrode material for remarkable electrochemical performance

The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg^?1, 168(±5) Fg^?1 and 186 (±5) Fg^?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs^?1, while it is found to be 114 (±5) Fg^?1, 136 (±5) Fg^?1 and 170 (±5) Fg^?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag^-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices.     

Effects of the loading and polymerization temperature on the capacitive performance of polyaniline in NaNO3

Polyaniline (PANI) synthesized by a potentiostatic method at 4 °C in 1 M HNO₃ with the polymerization charge density equal to/less than 0.45 C cm⁻² was demonstrated to exhibit ideally capacitive characteristics (i.e. high reversibility and high-power property) with a high specific capacitance of 210 F g⁻¹ for the application of electrochemical supercapacitors in NaNO₃. Influences of the polymerization charge density (i.e. the polymer loading) and the polymerization temperature on the capacitive characteristics of PANI films compared by both cyclic voltammetry and charge-discharge technique were reasonably correlated with their structural properties examined by X-ray photoelectron spectroscopy (XPS). The highest specific capacitance of a PANI film polymerized at 4 °C was attributed to its lowest density of structure defects. The surface morphology of these PANI films was examined by a scanning electron microscope (SEM).     

Effect of Electrodeposition Parameters on the Microstructure and Corrosion Behavior of ‎DCPD Coatings on Biodegradable Mg–Ca–Zn Alloy

In this study, DCPD (Brushite, CaHPO₄.2H₂O) coatings were prepared on the surface of a Mg–Ca–Zn alloy using different current density (0.15–1.2 mA/cm²) and deposition time (5–90 min). The results revealed that DCPD with needle‐like morphology was observed for the current density between 0.15 and 0.4 mA/cm²?, whereas ?plate‐like morphology was obtained at current density above 0.8 mA/cm². The results showed that surface roughness increased with increasing current density. The lowest corrosion rate of 0.14 mm/year was obtained for the dense and uniform DCPD coating ?at 0.4 mA/cm², while further increase has deleterious effect on the corrosion resistance.     

Facile Fabrication of Binder-Free CoZn LDH/CFP Electrode with Enhanced Capacitive Properties for Asymmetric Supercapacitor

CoZn layered double hydroxide (LDH) or Co(OH)₂ pseudocapacitive material has been prepared on the current collector of carbon fiber paper (CFP) using an eco-friendly one-step electrodeposition. Benefiting from its unique structural feature, the binder-free CoZn LDH/CFP electrode material realizes high specific capacitance of 1156 Fg^?1 at a current density of 1 Ag^?1 and excellent rate capability of 80% retention with 16 fold current density increment, which is much better than that of Co(OH)₂ (617 Fg^?1, 65%). Notably, the CoZn LDH/CFP can retain an outstanding electrochemical stability with a capacitance degradation of only 6% after 6000 charge–discharge cycles at 32 Ag^?1. Moreover, an asymmetric supercapacitor (ASC) using CoZn LDH/CFP as a positive electrode and AC/CFP as a negative electrode has been assembled. The ASC exhibits a superior energy density of 30.0 Whkg^?1 at a power density of 800 Wkg^?1 with a specific capacitance up to 84.4 Fg^?1 and a potential window wide to 1.6 V. These encouraging results indicate that CoZn LDH/CFP composite material has a great potential for next-generation energy conversion/storage devices.

     

Arsenic removal from drinking water by electrocoagulation using iron electrodes

Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm^?2), initial arsenic concentration (50–500 μg L^?1), operating time (0–15 min), electrode surface area (266–665 cm²), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L^?1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm^?2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm² taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L^?1 for electrode surface area of 266 cm². The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.     

The technology of the Li/BrCl in SOCl2 inorganic battery system: performance and self-discharge characteristics following long-term storage

Investigations were conducted on Li/BrCl in SOCl₂ cells to determine both the performance and shelf life characteristics after storage for a period of one year at various temperatures. Room temperature discharge test results indicate that there is little self-discharge in those cells stored at either room temperature or at ?40° C. Even when the cells were subjected to elevated storage temperatures, the discharge results show that the cells exhibit a low self-discharge rate. However, cells stored at an elevated temperature do exhibit a decreased rate capability when compared to those results obtained from fresh cells. From the 56 ohm load discharge performance results, the self-discharge rate for cells stored at ?40, 24, 50 and 72° C was calculated. Further, the activation energy over the temperature range was found to be 27.6±1.7 kJ. Also, the self-discharge rate was monitored under light load conditions. The results for Li/BrCl in SOCl₂ D cells discharged under a current density of 2.38 to 0.016 mA cm^?2, show that the operationally induced self-discharge rate reaches a maximum of 4.5μA cm^?2 for cells discharged under a current density of 0.034 mA cm^?2 and decreases to 2.9μA cm^?2 as the discharge current density decreases to 0.016 mA cm^?2. These data indicate that the self-discharge rate for cells discharged under very light loads may eventually approach that for cells stored under open circuit conditions.     

Core–Shell Structured Cellulose Nanofibers/Graphene@Polypyrrole Microfibers for All‐Solid‐State Wearable Supercapacitors with Enhanced Electrochemical Performance

Thanks to their considerable electrochemical and mechanical properties, fiber‐shaped supercapacitors have become the most potential energy storage devices for portable and wearable electronics in the future; however, challenges still exist in the pursuit of practical applications among them. In this work, ternary microfibers, which are composed of TEMPO‐oxidized cellulose nanofibers/reduced graphene oxide microfiber cores coated with polypyrrole shell layers, are successfully fabricated through industrializable and sustainable wet‐spinning and interfacial polymerization strategies. The prepared microfibers possess well‐defined microstructures and outstanding mechanical properties (559 MPa). When assembled into symmetrical all‐solid‐state fiber‐shaped supercapacitors (FSCs), they exhibit remarkable electrochemical properties (647 mF cm^?2, 14.37 µWh cm^?2 at 0.1 mA cm^?2), prominent cycling stability (92.5% capacitance retention and 92.6% coulomb efficiency after 10 000 cycles), and extraordinary flexibility (no significant decay in capacitance after 5000 bending cycles), which are superior to all the congeneric FSCs reported to date. The prominent performances are ascribed to the synergistic effect of the well‐designed ternary system and synergistic effects between interior components. The advantages in electrochemical, mechanical, and industrial properties of the ternary FSCs can provide reference and boost the development of flexible energy storage applications.     

Response of a proton exchange membrane fuel cell to a sinusoidal current load

The load-following capability of a proton exchange membrane fuel cell was studied by measuring the cell voltage response to a sinusoidal current load with large amplitude and varying frequency. A mathematical model was developed, incorporating mass transport and capacitive effects as well as the membrane resistance. The model was capable of separating the faradaic and capacitive currents and predicting the observed hysteresis. At frequencies of the sinusoidal current load below 1 Hz, no appreciable hysteresis in the polarisation curve was observed. When increasing the frequency above 1 Hz, a hysteresis appeared at current densities below 0.2 A cm^?2. The model related this hysteresis to capacitive effects. When using air as the cathode feed, hysteresis in the current density range 0.5 A cm^?2 and higher appeared above 1 Hz compared to 100 Hz for pure oxygen. The model revealed that hysteresis observed in this current density range was caused by oxygen transport limitations.     

Rational design of binder-free ZnCo2O4 and Fe2O3 decorated porous 3D Ni as high-performance electrodes for asymmetric supercapacitor

The development of hierarchical, porous film based current collector has created huge interest in the area of energy storage, sensor, and electrocatalysis due to its higher surface area, good electrical conductivity and increased electrode-electrolyte interface. Here, we report a novel method to prepare a hierarchically ramified nanostructured porous thin film as a current collector by dynamic hydrogen bubble template electro-deposition method. At a first time, we report a porous 3D-Ni decorated with ZnCo₂O₄ and Fe₂O₃ by simple, low-cost electrochemical deposition method. The fabricated porous 3D-Ni based electrodes showed an excellent electrochemical property such as high specific capacitance, excellent rate capability, and good cycle stability. The asymmetric solid-state supercapacitor device was fabricated using porous, 3D Ni decorated with ZnCo₂O₄ and Fe₂O₃ as the positive and negative electrodes. The fabricated ZnCo₂O₄//Fe₂O₃ asymmetric device delivered an areal capacitance of 92?mF?cm^?2 at a current density of 0.5?mA?cm^?2 with a maximum areal power density of 3?W?cm^?2 and areal energy density of 28.8?mWh?cm^?2. The higher performances of porous, 3D current collector have a huge potential in the development of high performance supercapacitor.     

Development of quasi‐solid‐state dye‐sensitized solar cell based on an electrospun polyvinylidene fluoride–polyacrylonitrile membrane electrolyte

Dye sensitized solar cell (DSSC) has been magnetizing more awareness in current research due to more efficiency. The foremost drawback of the solar cell is the evaporation of organic electrolyte. In order to address this problem, the polyvinylidene fluoride–polyacrylonitrile–Electrospinning Fibrous Membranes were prepared by electrospinning method and the photovoltaic performances were evaluated. The polyvinylidene fluoride and polyacrylonitrile were mixed in N,N′‐dimethylformamide and acetone at an applied potential of 15 kV. The surface morphology of membrane is interconnected with network structure and a large number of voids were observed from Field Emission Scanning Electron Microscopy images. The electrolyte uptakes up to 310% were observed and it shows an increase in the ionic conductivity up to 6.12 × 10^?2 S cm^?1 at 25°C. The fabricated DSSCs show open circuit voltage (V_oc) of 0.74 V, fill factor (FF) of 0.65 and short circuit current (J_sc) of 6.20 mA cm^?2 at an incident light intensity of 100 mW cm^?2. The photovoltaic efficiency also reached up to 3.09%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40022.     

The microstructural features and corrosion behavior of Hydroxyapatite/ZnO nanocomposite electrodeposit on NiTi alloy: Effect of current density

In the present study, hydroxyapatite/ZnO nanocomposite coatings were developed on NiTi superelastic alloy via pulse electrodeposition technique under three different current densities. The morphological observations (FESEM) indicated that under 6 mA/cm², a compact, uniform composite layer could form, whereas lower or higher current densities resulted in non-uniform, porous coatings with uneven distribution of nanoparticles. XRD and FTIR studies revealed that pure hydroxyapatite was not achieved below 6 mA/cm². Topographic features (AFM) were assessed and demonstrated a continuous rise in roughness parameters as current density increased. The corrosion behavior was investigated through potentiodynamic polarization as well as impedance spectroscopy techniques. According to the extracted data, the porosity and non-uniformity of coatings formed under 3 and 9 mA/cm² caused a detrimental effect on the corrosion resistance of surfaces. The layer obtained under 6 mA/cm² showed resistance (R_c) which was almost two times greater than those deposited under 3 and 9 mA/cm² current densities. Last but not least, the bioactivity of coatings was evaluated in simulated body fluid. It was observed that more compact deposits offered more active sites for apatite nucleation, resulting in refined cauliflower-like grains. Accordingly, it can be asserted that the best composite coating was achieved under 6 mA/cm² current density.     

A binder‐free Ir0.4Ru0.6‐oxide/functionalized multi‐walled carbon nanotube electrode for possible applications in supercapacitors

An initial study on a simple and inexpensive method to form an Ir_0.4Ru_0.6‐oxide (MMO) coating onto high‐area plasma functionalized multi‐walled carbon nanotubes (f‐MWCNTs) at the bench‐scale for possible supercapacitor (SC) applications is presented. f‐MWCNT electrodes are prepared in a two‐step process combining the growth of MWCNTs directly onto a 316 stainless steel mesh by thermal‐chemical vapour deposition (t‐CVD), followed by the addition of oxygen‐containing functionalities to their surface by plasma functionalization. The plasma functionalization step is done to: (i) improve electrode wettability and (ii) improve capacitive properties through the addition of pseudocapacitive oxygen functionalities. A simple dip‐dry method is then employed to coat the f‐MWCNTs with the desired MMO coating (Ir_0.4Ru_0.6‐oxide) prepared initially in a liquid precursor mixture. f‐MWCNT electrodes are suspended and dipped into the precursor then heated in air to evaporate the solvent while building the oxide layer. The resulting MMO/f‐MWCNT electrode exhibits excellent stability in 4 mol/L KOH electrolyte, yielding larger specific capacitance values than those obtained on bare f‐MWCNT electrodes; at a charging/discharging current density of 0.5 mA cm^?2, the MMO/f‐MWCNT and f‐MWCNT electrodes achieve specific capacitances of 664 ± 7 and 190 ± 30 F g^?1 in a 3‐electrode cell, respectively. The MMO/f‐MWCNT electrodes show good rate capability performance up to 10 mA · cm^?2 and excellent stability.