High capacity natural fiber coated conductive and electroactive composite papers electrode for energy storage applications

Flexible, lightweight, and environment friendly energy storage devices are in high demand of modern disposable technology. This study presents the coating of directly collected lignocelluloses fibers from self-growing plant, Monochoria vaginalis with conducting layers of polypyrrole and polyaniline. Fabricated paper electrodes were conductive, electroactive, all-organic constituents, flexible, and can be cut with help of scissor in any shape. Paper electrodes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis for morphology, structural, and thermal characteristics, respectively. Furthermore, fabricated paper electrodes were characterized by cyclic voltammetry to confirm the electroactive behavior and showed excellent electrochemical performance. Paper sheets comprising lignocelluloses fibers and polypyrrole coating (LC/PPy) were employed as electrodes of symmetric cell and showed specific capacitance of 230.35 Fg⁻¹ at current density 0.25 mA g⁻¹ for LC/PANI, while LC/PPy showed 9.042 W h kg⁻¹ and 91.33 W kg⁻¹ energy density and power density, respectively. This paper electrodes are highly feasible for environmentally safe and flexible energy storage applications, particularly in era of modern disposable technology. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47282.     

In-situ AFM and EIS study of a solventborne alkyd coating with nanoclay for corrosion protection of carbon steel

A solventborne alkyd composite coating containing modified montmorillonite (MMT) nanoclay was made on carbon steel, and its corrosion protection was investigated by in-situ atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) measurements in 3 wt.% NaCl solution. X-ray diffraction (XRD) analysis indicated intercalation of the MMT sheets in the composite coating. Thermo-gravimetric analysis (TGA) demonstrated improved thermal stability of the composite coating due to the modified nanoclay. Scanning electron microscopy (SEM) and AFM examination revealed dispersion and also some aggregation of the nanoclay particles in the coating. In-situ AFM images show a stable coating surface at nano-scale during relative long time exposure in the NaCl solution, indicating an enhanced stability of the composite coating. The EIS results confirmed that the composite coating provides an enhanced barrier type corrosion protection for carbon steel in the corrosive solution, which could be attributed to the intercalated lamellar MMT sheets in the coating that block the defects and decrease the transport of water and corrosive species.     

Microwave combustion synthesis,magneto-optical and electrochemical properties of NiMoO4 nanoparticles for supercapacitor application

Nickel molybdate (NiMoO₄) nanoparticles (NPs) were synthesized by a simplistic one-pot microwave combustion method using urea as the fuel. The produced NPs have been examined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) analysis, scanning electron microscope (SEM), energy dispersive X-ray (EDX), high-resolution transmission electron microscopy (HR-TEM) analysis. Further, optical and electronic properties were determined by UV-Visible and Photoluminescence (PL) analysis, respectively. The magnetic performance of the NiMoO₄ NPs was investigated by vibrating sample magnetometer (VSM) and the surface chemical composition was identified by X-ray photoelectron spectroscopy (XPS). The electrochemical activities of the NiMoO₄ NPs were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD) analysis. From the results, the CV curves indicated the occurrence of redox couples and besides with the EIS data (Nyquist plot), confirmed the supercapacitor nature of the synthesized NiMoO₄. The prepared NiMoO₄ exhibits a high specific capacitance and rateability. This electrode grants a high specific capacitance of 450?F?g^?1 at 2?mA?cm^?2 and the well permanency with a cycling proficiency of 94% after 1000 cycles. These results clearly showed that the synthesized NiMoO₄ NPs have potential application for the forthcoming flexible and lightweight energy storage.     

Preparation of polyaniline/multiwalled carbon nanotube composite by novel electrophoretic route

A nano-structured composite film comprising of emeraldine salt (ES) and carboxyl group functionalized multiwalled carbon nanotubes (MWCNT-c) has been electrophoretically prepared from their colloidal suspension on an indium-tin-oxide (ITO) coated glass plate. This nano-structured composite film (ES/MWCNT-c) has been characterized using atomic force microscopy (AFM), ultraviolet-visible (UV-visible) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The AFM studies reveal porous morphology with uniformly distributed MWCNT-c in this composite film. The SEM and TEM investigations reveal wrapping of MWCNT-c with the chains of ES. UV-visible and FT-IR investigations show the formation of MWCNT-c doped composite at the molecular level. The results of the CV and EIS studies indicate enhanced electrochemical and charge transfer behavior of the composite. The application of ES/MWCNT-c/ITO electrode to biosensor for cholesterol indicates short response time (10 s) and high sensitivity (6800 nA mM⁻¹).     

一种生物炭基柔性固态超级电容器的制备及性能研究

利用固体农业废弃物玉米秸秆作为原料,经高温煅烧,KOH刻蚀获得具有较大比表面积的多孔生物炭材料,并采用粉末X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)、红外光谱(FT-IR)、拉曼光谱(Raman)以及比表面积和孔径分析仪(BET)等表征手段,研究其物理、化学结构和微观形貌。结果表明,所制备的生物炭材料具有发达的“微孔-中孔-大孔”三维贯通多级孔道结构,比表面积高达1228 m2·g^-1。将其作为电极材料,与H₂SO₄/PVA凝胶电解质可组装成为具有柔性的全固态超级电容器。利用循环伏安测试(CV)、恒电流充放电(GCD)以及交流阻抗测试(EIS)对柔性超级电容器电化学性能进行了测试。在电流密度为1.0 A·g^-1的条件下,其比容量可达125 F·g^-1。该器件具有良好的机械柔性和电化学稳定性,将其从0°弯曲至180°的过程中,比电容保持率约为93.5%;以不同弯曲角度将其连续弯折100次后,仍能保持较高的比电容。此外,在弯折角度180°、充放电电流密度为5.0 A·g^-1 的条件下经过500次循环充放电后,比电容值保持率约为95.6%,库仑效率约为94.9%。说明所制备的柔性超级电容器具有优异的充放电性能和长效循环稳定性。作为一种柔性、质轻、便携的储能装置,在可穿戴电子器件领域内具有潜在应用价值。同时该方法也为固体农业废弃物玉米秸秆的高附加值转化利用和新型绿色能源器件创新研制提供了新的技术途径。     

Mica/polypyrrole (doped) composite containing coatings for the corrosion protection of cold rolled steel

Micas/polypyrroles (PPys) doped with molybdate, p-toluene sulfonate, dodecyl benzene sulfonate, and 2-naphthalene sulfonate composite pigments were synthesized by chemical oxidative polymerization and characterized in coatings for corrosion protection on cold rolled steel substrate by various electrochemical techniques. Synthesized composite pigments were characterized for morphology by scanning electron microscopy, which indicated physical formation of PPy on the surface of mica. Chemical composition of the composite pigments was analyzed by X-ray photoelectron spectroscopy which chemically confirmed doped PPy formation on the mica surface. Coatings were formulated at 20% pigment volume concentration (composite pigments or as-received mica pigment) and were applied on cold rolled steel substrate. Coatings were exposed to salt spray test conditions (ASTM B117) for 30 days and were periodically assessed for corrosion with electrochemical impedance spectroscopy (EIS), open circuit potential (OCP), and potentiodynamic polarization. EIS and circuit modeling results demonstrated higher coating resistance (R _c) for mica/PPy (doped) composite coatings as compared to as-received mica pigment containing coating after 30 days of salt spray exposure. Lower current density and more positive corrosion potential values were observed for mica/PPy (doped) composite coatings as compared to mica pigment-based coating in potentiodynamic polarization measurements, indicating improved corrosion protection for cold rolled steel substrate. OCP measurements revealed more positive values for mica/PPy (doped) composite coatings as compared to mica pigment-based coating suggesting superior corrosion protection for mica/PPy (doped) composites.     

Effect of nickel content on the electrochemical behavior of Cu-Al-Ni alloys in chloride free neutral solutions

The electrochemical behavior of Cu-Al-Ni alloys in chloride free neutral solutions was investigated. The effect of Ni content on the corrosion resistance of the alloys was examined and evaluated. Conventional electrochemical techniques and electrochemical impedance spectroscopy, EIS, have been used. Potentiodynamic measurements revealed that the increase in the Ni content decreases the stability of the Cu-Al-Ni alloys. The polarization measurements were confirmed by EIS experiments. The morphology of the alloy surface was investigated by scanning electron microscopy, SEM, and surface analysis was made by energy dispersive X-ray technique. The experimental impedance data were fitted to theoretical data according to a proposed equivalent circuit model representing the electrode/electrolyte interface. The results of these experiments are discussed in reference to the potential-pH (Pourbaix) diagrams of the alloying elements.     

Sol-gel–mediated synthesis of TiO2 nanocrystals: Structural,optical, and electrochemical properties

Nanoparticles of titanium dioxide were prepared using the sol-gel method without any impurity. Rietveld refinement of XRD data confirmed the anatase phase of synthesized nanoparticles with space group I4_1/amd (141). XRD pattern revealed the crystalline nature of synthesized nanopowder. The average crystallite size of synthesized nanoparticles was calculated 7.5 nm. The electrochemical performance of synthesized TiO₂ nanopowder was investigated as working electrode. The electrochemical reaction was found diffusion-controlled as observed from cyclic voltammetry (CV) studies at different scan rates. The diffusion-controlled charge storage mechanism also confirmed by charge transfer resistance and Warburg impedance, as calculated from the EIS analysis. SEM micrograph showed the plate-like structure grown in cluster cloud of particles of synthesized TiO₂ nanocrystals. Absorbance and optical bandgap were obtained using UV-Vis spectra. De-convoluted PL spectra provided the emission pattern from the ultra-violet region to green region due to the presence of interstitial oxygen vacancies. The tune bandgap with EIS measurements of synthesized TiO₂ nanoparticles offers its potential application in energy storage devices and photovoltaic applications.     

电解质对卵磷脂双分子层电化学行为的影响

实验利用自组装技术在铂电极上制备支撑的卵磷脂双层膜（s-BLM）作为生物膜的模型,利用循环伏安法（cV）和电化学阻抗谱（EIS）对由电解质KCI引起的s-BLM通透性的变化进行了研究。结果表明,KCI可与s-BLM发生较强的相互作用,导致s—BLM表面磷脂分子的有序排列受到影响,产生一些离子通道,增加了对探针分子电流响应,同时降低了s—BLM的电阻。     

Electrochemical and magneto-optical properties of cobalt molybdate nano-catalyst as high-performance supercapacitor

Nanorod shaped cobalt molybdate (CoMoO₄) electro-catalysts synthesized by microwave combustion route using urea as the fuel. The formation of monoclinic nanocrystalline structure, metal-oxygen (M–O) and chemical bonding was confirmed by X-ray powder diffractometry (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopy, respectively. Scanning electron microscope (SEM) associated with energy dispersive X-ray (EDX) and high-resolution transmission electron microscope (HR-TEM) were used to confirm the morphology, elemental composition and particle size of the samples, respectively. The optical and defects were confirmed by the UV–vis. absorption and photoluminescence (PL) spectroscopy at room temperature (RT). The room temperature magnetic behaviors of product were investigated by vibrating sample magnetometer (VSM). Surface binding energy and element confirmation were examined by X-ray Photoelectron spectroscopy (XPS). The electrochemical (EC) performance was studied by cyclic voltammetry (CV), galvanostatic charge-discharge analysis (GCD) and electrochemical impedance spectroscopy (EIS) analysis. The CV curve proved the existence of redox pairs and the supercapacitor nature exhibited by the EIS (Nyquist plots). The GCD studies provided the non-symmetrical discharge curves and the highest specific capacitance (Csp) of ~ 133?F/g were acquired at a constant discharge current density (1?mA/cm^?2). The cyclic stability investigations revealed capacitance retention of about 100% after 1000 cycles, proposing the prospective usage of CoMoO₄ in energy-storage devices.     

Fabrication and characterization of MnO2 based composite sheets for development of flexible energy storage electrodes

Development of cost efficient, flexible and light weight paper electrodes for high-tech applications is high in demand in era of modern disposable technology. In this study α-MnO₂ nanorods were fabricated through hydrothermal method by varying growth time and further combined with lignocelluloses fibers extracted from self growing plant, Monochoria Vaginalis. Crystal structure, morphology and thermal properties of MnO₂ nanorods were characterized by X. Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Thermogravimetric Analysis (TGA), respectively. FESEM image analysis revealed the highest aspect ratio of 48.016 for 4?h treated MnO₂ sample and high purity level was confirmed by XRD. MnO₂ sample with high aspect ratio, relatively pure and larger yield was selected for incorporation of lignocelluloses fibers to fabricate flexible, light-weight and environmentally safe LC/MnO₂ composite paper sheet. Furthermore, LC/MnO₂ composite sheet was employed as working electrode in 2?M sodium sulfate electrolyte for cyclic voltammetry measurements. Presented LC/MnO₂ composite sheet revealed specific capacitances 117, 59, 39, 25 and 23?F/g at scan rates of 5, 10, 20, 50 and 100?mV/s, respectively. Incorporation of LC fibers within MnO₂ nanorods as binders will open the possibilities to fabricate the flexible paper electrode for application in supercapacitors and batteries due to facile synthesis, light-weight and environmentally friendly aspects.     

Preparation and electrochemical properties of sulfur-acetylene black composites as cathode materials

A sulfur-acetylene black (AB) composite was synthesized by thermally treating a mixture of sublimed sulfur and AB. The sulfur-AB composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) tests. From the results, we confirmed that sulfur was well dispersed on nano-scale and embedded inside nano-pores of the acetylene black with the steric chain structure in the composite. The electrochemical performance of the composite as cathode materials was evaluated by the galvanostatic method, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). The sulfur-AB composite, which can effectively confine the diffusion of dissolved polysulfides in organic electrolyte and stabilize the structure during the charge and discharge process, showed high capacity and good cycle performance. The discharge capacity of the sulfur-AB composite was maintained at 500 mAh/g after 50 cycles.     

Flame retardant ethylene‐vinyl acetate composites based on layered double hydroxides with zinc hydroxystannate

Mg‐Al‐Fe ternary layered double hydroxides (LDH) were synthesized based on red mud (RM) by calcination‐rehydration method, and characterized using X‐ray diffraction (XRD). And, the LDH coated with ZnSn(OH)₆ (ZHS) was studied by XRD, scanning electron microscopy (SEM), transmission electron microscopy, and energy dispersive spectroscopy (EDS). The flame retardant and thermal properties of EVA composites based on RM, LDH and LDH coated with ZHS were studied using cone calorimeter test (CCT) and thermogravimetric analysis (TGA). The CCT data indicates that heat release rates (HRR) of EVA with LDH coated with ZHS decreases in comparison with that of EVA, EVA/RM and EVA/LDH composites. The TGA data show that LDH coated with ZHS can apparently increase the thermal stability and the charred residues after burning. POLYM. ENG. SCI., 54:2918–2924, 2014. © 2014 Society of Plastics Engineers     

Electrochemical atomic layer deposition of a CuInSe2 thin film on flexible multi-walled carbon nanotubes/polyimide nanocomposite membrane: Structural and photoelectrical characterizations

This study describes a method for the fabrication of an electrochemical atomic layer deposition (EC-ALD) used to fabricate the ternary, semiconducting compound, CuInSe₂ (CISe), onto a flexible, carboxyl-functionalized multi-walled carbon nanotube/polyimide (COOH-MWCNT/PI) nanocomposite membrane. The elements were deposited using amperometric methods (I–t) in the following sequence: Se/Cu/Se/In/Se/Cu/Se/In and so on, in which the optimum deposition potential for each element was obtained via a cyclic voltammetry (CV) technique. Field emission scanning electron microscopy (FE-SEM) showed that the deposits consisted of many spherical nanoparticles, and energy dispersive spectroscopy (EDS) analysis indicated that the atomic ratio of the deposits (CuInSe) was 1.14 1.00 2.18, similar to the stoichiometric value of the compound. Near Fourier transform infrared spectroscopy (FT-IR) transmission measurements provided a band gap of 1.05 eV, which was confirmed by the absorption spectrum. Open-circuit potential (OCP) and current-voltage (I–V) measurements showed the resulting composite had a good p-type property. CISe spherical NPs electrodeposited on the CNTs/PI membrane may have promising applications in optoelectronic nanodevices and nanotechnologies; in addition, the CNTs/PI membrane could be used as raw material for manufacturing solar cells.     

Influence of ionic substitution in improving the biological property of carbon nanotubes reinforced hydroxyapatite composite coating on titanium for orthopedic applications

The present work is aimed for the development of carbon nanotubes (CNTs) reinforced single mineral (Sr, Mg, Zn) as well as multi minerals (Sr+Mg+Zn) substituted hydroxyapatite composite (M-HAP) coatings on titanium (Ti). The effect of different mineral ions substitution and CNTs reinforcement in HAP composite coating is discussed in detail. Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), and high resolution transmission electron microscopy (HRTEM) were used to characterize the structural and morphological behavior of the composite coatings. The corrosion resistance of the composite coatings in simulated body fluid (SBF) solution was evaluated by the potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies. In addition, the biocompatibility of the composite coatings was evaluated by in vitro culture of human osteoblast MG63 cells on the composite coated Ti. All these results essentially suggest that CNTs/M-HAP composite coated Ti can be a potential candidate for orthopedic applications.     

Physical and electrochemical characterization of CdS hollow microspheres prepared by a novel template free solution phase method

Novel CdS hollow microspheres have been successfully synthesized via a facile template-free solution-phase reaction from cadmium nitrate and thioacetamide precursors. The morphology of CdS hollow microspheres depends strongly on the ratio between the precursors, cadmium nitrate to thioacetamide ratio. The physical properties of the hollow microspheres have systematically been studied by different characterization methods. The stoichiometry of the hollow microspheres studied by the energy dispersive X-ray diffraction spectroscopy confirmed that the synthesized CdS hollow microspheres are nearly stoichiometric bulk like CdS. The morphology of the hollow microspheres studied by high resolution scanning electron microscopy and transmission electron microscopy observations showed that the CdS hollow microspheres of the size of 2.5 μm have hollow structure and are constructed by several nanoparticles of the size between 30 and 40 nm. The UV-visible diffuse reflectance spectroscopy studies showed that the band gap of the CdS hollow microspheres increased while increasing the cadmium nitrate to thioacetamide ratio. Further electrochemical characterization of CdS hollow microspheres was performed with glassy carbon electrode (GCE) after its chemical modification by CdS dispersed in dimethylformamide. The electrochemical studies showed that with decreasing the band gap energy the electron transfer resistance of CdS/GCE was also found decreased. Moreover, electrochemical impedance spectroscopic measurements showed enhanced DNA adsorption onto CdS/GCE in comparison to GCE. These experiments demonstrate that the CdS hollow microspheres act as an efficient electrode modifier that effectively decreased the charge transfer resistance and capacitance of the modified sensors, which can be used for electroanalytical purposes.     

Anticorrosive coating based on poly(vinyl acetate) formed by electropolymerization on the copper surface

The poly(vinyl acetate) (PVAC) film was obtained by electropolymerization on the copper electrode using cyclic voltammetry performed in mixed electrolyte based on water/ethyl alcohol/acetic acid containing vinyl acetate (VAc) and benzoyl peroxide as polymerization initiator. The coatings were characterized by optical microscopy, scanning electron microscopy (SEM) and infrared (IR) spectroscopy. The corrosion was induced in hydrochloric acid solution using potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The microscopic and SEM images revealed the PVAC coating formation and IR spectroscopy confirmed that it exhibits the same characteristic bands as a standard PVAC sample. From the potentiodynamic polarization, the PVAC protective performance of 78% was computed. The EIS measurements showed the occurrence of the surface adsorbed layer with a higher impedance response to the frequency and a phase angle maximum shifted to lower values than those of uncoated samples. In addition, the VAc electropolymerization mechanism was discussed and the PVAC adsorption mechanism on the copper surface was proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47320.     

Synergistic effect in structural and supercapacitor performance of well dispersed CoFe2O4/Co3O4 nano-hetrostructures

Herein, we report a facile homogeneous urea – assisted hydrothermal approach for the design of CoFe₂O₄/Co₃O₄ nano hetrostructure. A variation in Co concentration leads to smartly designed composite material namely CFC-11 and CFC-12 where CFC-12 appreciates the benefits of both CoFe₂O₄ and Co₃O₄ nanoparticles. The physico – chemical properties of as developed materials were investigated by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron microscopy (XPS) and Raman spectroscopy. The specific surface area and pore size distribution was determined by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halendo (BJH) respectively. Magnetic measurements via. vibrating sample magnetometer (VSM) demonstrate that saturation magnetization decreases with the incorporation of Co₃O₄ antiferromagnetic nanoparticles. To explore the utility of as designed nano-hetrostructures as supercapacitor electrodes, we employed cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS) measurements. A high specific capacitance of 761.1?F?g^?1 at 10?mV?s^?1, admirable cyclic durability of 92.2% and a low resistance value obtained from impedence measurements was observed for CFC-12. The favorable performance demonstrates the synergistic effect of CoFe₂O₄ and Co₃O₄ nanoparticles and thus promise an excellent material for energy storage devices.     

Hydroxyapatite Mineralization on the Calcium Chloride Blended Polyurethane Nanofiber via Biomimetic Method

Polyurethane nanofibers containing calcium chloride (CaCl2) were prepared via an electrospinning technique for the biomedical applications. Polyurethane nanofibers with different concentration of CaCl2 were electrospun, and their bioactivity evaluation was conducted by incubating in biomimetic simulated body fluid (SBF) solution. The morphology, structure and thermal properties of the polyurethane/CaCl2 composite nanofibers were characterized by means of scanning electron microscopy (SEM), field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetry. SEM images revealed that the CaCl2 salt incorporated homogeneously to form well-oriented nanofibers with smooth surface and uniform diameters along their lengths. The SBF incubation test confirmed the formation of apatite-like materials, exhibiting enhanced bioactive behavior of the polyurethane/CaCl2 composite nanofibers. This study demonstrated that the electrospun polyurethane containing CaCl2 composite nanofibers enhanced the in vitro bioactivity and supports the growth of apatite-like materials.