Increasing Scan Rate Research Articles

Synthesis, characterization, electrochemistry, biological and molecular docking studies of the novel Co(II), Ni(II) and Cu(II) complexes derived from methanethiol bridged (2-((1H-benzo[d]imidazol-2-yl)methylthio)-1H-benzo[d]imidazol-6-yl)(phenyl)methanone

The bio-active Co(II), Ni(II) and Cu(II) complexes derived from new (2-((1H-benzo[d]imidazol-2-yl)methylthio)-1H-benzo[d]imidazol-5-yl)(phenyl)methanone were synthesized in good yield. The structure of these metal complexes have been characterized using IR, Uv–visible, mass spectra,1H NMR, TGA and powder XRD techniques. The spectral data of the Co(II) and Ni(II) complex indicated the tri-dentate bonding mode with the ligand and that of the Cu(II) complex is in bi-dentate bonding mode. The electrocatalytic activity of the Co(II) complex was studied by cyclic voltammeter using modified GCE towards various concentration of dopamine (DA, 3,4-dihydroxyphenethylamine). The obtained Ip value linearly increased with increasing scan rates, indicating the oxidation process of dopamine (DA) which occurred by modified Co(II) complex/GCE through diffusion controlled process. The antimicrobial, antioxidant and cytotoxicity studies of the ligand and its metal complexes were performed, the obtained results showed that the complexes are more potent bio-active as compared with uncoordinated ligand. The DNA binding property of the metal complexes were performed on double strand calf thymus DNA using electronic absorption and fluorescence emission methods, in addition, photo induced DNA cleavage activity also studied on pBR322 DNA. The molecular docking of the Co(II) complex on 6-bp DNA (PDB code: 1Z3F) and C-KIT Tyrosive kinases (TRKs) (PDB code: 1t46), further confirms the inhibition ability of the metal complex. The experimental results and the drug likeness property of the metal complexes suggest the possible applications of metal complex which, could be developed as a potent drug in the near future.

Electroreduction of Dy(III) assisted by Zn and its co‐deposition with Zn(II) in LiCl–KCl molten salt

To recover dysprosium (Dy) from LiCl–KCl molten salt, the electrochemical mechanism of Dy(III) on liquid Zn electrode and co‐deposition of Dy(III) and Zn(II) on W electrode were studied using electrochemical methods. Cyclic voltammetry results demonstrated that the redox process of Dy on liquid Zn electrode is reversible and controlled by diffusion. Reverse chronopotentiograms showed that the transition time ratio of reduction and oxidation is ~3:1, revealing the redox of Dy on liquid Zn electrode is a kind of soluble–soluble system: Dy(III) + 3e− = (Dy–Zn)solution. The half‐wave potential of Dy(III) was almost constant with the increase in scanning rate. The electrochemical separation of metallic Dy from the molten salt was performed using constant potential electrolysis, and the product characterized using X‐ray diffraction and scanning electron microscopy–energy‐dispersive X‐ray spectroscopy was the thermodynamic unstable compound DyZn5. Also, the co‐deposition mechanism of Dy(III) and Zn(II) was explored, indicating that Dy(III) could deposit on pre‐deposited Zn and form Dy–Zn compounds: Zn(II) + 2e− = Zn and xDy(III) + yZn + 3xe− = DyxZny. Moreover, the effect of Dy(III) concentration on the formation of Dy–Zn compounds was investigated. The redox peak currents corresponding to different Dy–Zn compounds changed with the increase in Dy(III) concentration. The co‐deposition of Dy(III) and Zn(II) was performed using constant current electrolysis at diverse Dy(III) concentrations. The different Dy–Zn compounds were produced by controlling Dy(III) concentration.

Swift heavy ions irradiated PVDF/BaTiO3 film as a separator for supercapacitors

Swift heavy ion (SHI) irradiated PVDF and (0.8)PVDF/(0.2)BaTiO3 films (thickness ~ 0.06 μm) have been studied as a separator for supercapacitors. Samples were irradiated by O6+ and Li3+ ions at fluence 2 × 1011 and 2 × 1012 ions/cm2, respectively. The irradiation-induced α → β phase transition in the PVDF polymer matrix, whereas complete amorphization in BaTiO3 filler is observed in nanocomposite films. The estimated value of percentage porosity (P%) for the irradiated composite films is comparable to the P% values for commercially available Cellulose separators. The flexibility is retained even after irradiation owing to irradiation-induced cross-linking in the PVDF matrix. The Cyclic Voltammetry (CV) curves retain their shape without distortion with increasing scan rate (20–180 mA s−1) showing the high rate performance of the separators. The electrochemical impedance spectra of Ni/separator/Ni blocking cells after the 1st and 200th cycles are analyzed to evaluate the bulk electrolyte resistance (Rbe) and conductivity under the cyclable performance of the separator films. The Rbe for the 1st cycle for irradiated PVDF and (0.8)PVDF/(0.2)BaTiO3 separator films are ranged from 0.4–1.4 Ω, which is much lower than Rbe for commercially available non-porous Celgard™ 2500 (88.2 Ω) and micro-porous Celgard Ez 2090 (47.1 Ω) separators. However, the conductivity values are higher than that of commercially available Cellulose and Celgard™ 2500 separators.

NO Detection By Cyclic Voltammetry with Platinum Electrodes on YSZ

Introduction Solid electrolyte sensors (SES) based on yttria stabilized zirconia (YSZ) can be used to detect traces of other components in inert gases such as Ar or N2. The O2--conducting solid electrolyte YSZ is thermodynamically highly stable and can be operated at high temperatures with stationary (potentiometry, amperometry) or dynamic methods (pulse polarization [1], cyclovoltammetry (CV) [2]). In the stationary mode, the selectivity of such sensors is limited to an extend that it is usually not possible to distinguish between individual gas components. In contrast to that, dynamic methods allow a significantly increased selectivity by using different rates of electrode reactions of the individual components in order to detect them independently in a gas mixture [2]. Dynamic electrochemical methods have been successfully used in liquids for many decades, and preliminary investigations on solid electrolyte gas sensors also show that such methods can be used to measure the concentrations of several redox-active gases, for example, oxygen and carbon monoxide [3]. The commercial solid electrolyte sensor used in this work was previously successfully tested to measure selectively different gases such as hydrogen, oxygen and water vapor [4] in nitrogen by using CV. In this work, these studies will be continued to investigate the ability of CV for selective detection of nitrogen oxides (NOx) and to elucidate the mechanisms of signal formation. Experimental setup The experimental setup shown in Fig. 1 and described in detail in [2] was used to adjust the O2 concentration (SES 1) and the measurement of the concentrations of O2 and NO in nitrogen (SES 2). Both SES of the type "Test gas, Pt|YSZ|Pt, air" contain a YSZ-tube equipped with two cylindrical platinum mesh electrodes at the inner and outer surface. The area of the inner measuring electrode was estimated by SEM to be about 3.5 cm2. A porous YSZ sintered layer was applied to join electrolyte and electrodes. Covering large parts of the reference and measuring electrode this porous layer offers an extended three-phase boundary for the oxygen transfer.SES 1 was continuously polarized during each experiment providing a constant O2 concentration in the purified carrier gas N2. At SES 2, the CVs were obtained at polarization voltages between -0.1 and -0.9 V against the Pt air reference electrode and scan rates in the range 100 ... 5000 mV/s. In each experiment, the second cycle was evaluated to obtain reproducible results. Between two consecutive cyclovoltammograms (CVM), the open circuit potential (OCP) was measured to monitor depolarization of the measuring electrode. Results and discussion The CVMs shown in Fig. 2 exhibit NO-related peaks developing in the cathodic scan direction between -0.2 and -0.7 V at scan rates between 100 and 2000 mV/s. The peak maximum shifts in the cathodic direction with increasing scan rate. The highest sensitivity was achieved at 2000 mV/s for 650 °C. At higher scan rates it decreases again. This is apparently caused by the shift of the oxygen reduction peaks from range -0.1 ... -0.3 V at lower scan rates to the cathodic direction at higher scan rates and leads to their superposition with the NO peaks. The curve shifts to higher electrolysis currents with increasing NO-concentration in the cathodic region, visible for every scan rate at U < -0.7 V correspond to the Faraday currents calculable for the NO reduction. The different peak potentials for O2 and NO enable a highly selective determination NO in O2 containing gases at scan rates between 200 – 2000 mV/s at concentrations c(NO) ≥ 10 vol.-ppm.The height of the NO peak as a suitable NO-related signal was calculated and plotted in Fig. 3 for different scan rates. This peak height rises almost linearly with the NO concentration and the curve slopes increase with the scan rate up to 2000 mV/s. Further investigations revealed that this scan rate-induced slope increase depends also on flow rate.OCP measurements at different NO concentrations and sensor temperatures (Fig. 4) indicate the known tendency of NO to decompose at hot and catalytically active platinum electrodes into N2 and O2. Therefore, in the investigated temperature range, the absolute value of the OCP decreases with increasing NO concentration, coming with rising oxygen partial pressure according to NO decomposition. Another process guiding the OCP in the NO-free carrier gas is the electronic conductivity of the solid electrolyte that increases exponentially with temperature [5].

Hydrothermal synthesis of quantum dots dispersed on conjugated polymer as an efficient electrodes for highly stable hybrid supercapacitors

Hydrothermal synthesis of graphene quantum dots (GQDs) composited with conjugated polymer were investigated the high specific capacitance and cyclic stability of supercapacitor. The situ chemical polymerization method was employed to synthesize the polypyrrole - graphene quantum dots (PPY-GQDs) composite at different concentrations of GQDs. The size, morphology and structural phase of the PPY- GQDs composites was studied by using Transmission Electron Microscope (TEM), Field Emission Scanning Electron Microscope (FESEM), Atomic Force Microscope (AFM) and X-ray diffractometry (XRD) techniques respectively. The optical and electrochemical measurements were carried out by using Ultraviolet-Visible (UV--Vis) Absorption spectroscopy, Photoluminescence Spectroscopy (PL) and electrochemical work station. The cyclic voltammetry (CV) results show enhanced current density and area of CV loop with increasing scan rate and the concentration of GQDs. The Supercapacitor was fabricated by two electrodes owns a high energy density 67.8 Wh/kg and 93 Wh/kg at a power density of 1210 W/kg and 1430 W/kg for PGC1 and PGC3 composites. The highest specific capacitance values 467.32 and 647.54F/g are achieved by PGC1 and PGC3 composite compare to pure PPY. The PPY-GQDs composites achieved excellent cycle stability until the 2000 cycle. Thus, it demonstrates that GQDs is playing a unique and important role in improving the performance of a hybrid supercapacitor device.

Enhanced Electrocatalytic Performance of Pt Nanoparticles Incorporated CeO2 Nanorods on Polyaniline-Chitosan Support for Methanol Electrooxidation (Experimental and Statistical Analysis)

Here, CeO2 nanorods (CeO2NRs) were successfully synthesized and characterized. Pt nanoparticles were synthesized in the presence of CeO2NRs and the matrix of polyaniline (PA) and chitosan (CH) as support to prepare the novel Pt-CeO2NRs/PA-CH nanocomposite. The electrocatalytic performance of Pt-CeO2NRs/PA-CH was investigated for methanol oxidation (MO) through chronoamperometry, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Durability of the prepared catalyst was also evaluated. The effects of several factors such as temperature, methanol concentration and scan rate were also studied for MO experimentally and statistically. Pt-CeO2NRs/PA-CH had enhanced electrocatalytic activity, compared to Pt/PA-CH, revealing that it would be a promising catalyst for MO in fuel cells. The variations of anodic peak potential and current density of MO with three main factors (temperature, concentration and scan rate), their binary and triple interactions were investigated statistically. The results showed that both anodic peak potential and current density can be significantly affected by main factors and their interactions at 0.05 level of probability. Meanwhile, the proposed statistical models can accurately estimate the variation of peak potential and current density with studied factors. The results showed that increase in temperature and scan rate leads to the enhancement of both responses.

Analysis of Charge Storage Behavior in Redox‐electrolyte Based Battery‐like‐systems: A Case Study on Zr‐doped Ceria

AbstractRedox‐additives are used as a cost‐effective means to improve low‐temperature charge‐storage capacity for aqueous‐supercapacitors. From a technology‐development standpoint, there are challenges associated with a lack of standard techniques to measure the redox‐additive based device‐parameters. This, in turn, yields a relatively poor understanding of the charge‐storage processes, especially in battery‐like supercapacitors. With this as a backdrop, this work undertakes an analysis of Ce0.9Zr0.1O2@Ni‐foam/KOH‐K3Fe(CN)6 electrode/electrolyte system. Here, a method is presented that enables the delineation of the contribution of the effective‐mass of the redox‐additive on the electrode‐surface. This method demonstrates that the effective electrolyte‐mass has a ∼38.5 to ∼15% contribution toward charge‐storage with increasing scan rates (1 to 80 mV s−1). The diffusion‐controlled trends are duly analyzed using the well‐established Trasatti analysis; these also serve as a reasonable benchmark for the method reported here. Hence the method is expected to be of use for other hybrid‐supercapacitor systems as well.

Parallel Detection of Fundamental and Sixth Harmonic Signals Using an ICR Cell with Dipole and Sixth Harmonic Detectors.

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is a powerful instrument for high-resolution analysis of biomolecules. However, relatively long signal acquisition periods are needed to achieve mass spectra with high resolution. The use of multiple detector electrodes for detection of harmonic frequencies has been introduced as one approach to increase scan rate for a given resolving power or to obtain increased resolving power for a given detection period. The achieved resolving power and scan rate increase linearly with the order of detected harmonic signals. In recent years, ICR cell geometries have been investigated to increase the order of the harmonic frequencies and enhance harmonic signal intensities. In this study, we demonstrated PCB-based ICR cell designs with dipole and sixth harmonic detectors for parallel detection of fundamental and harmonic (6f) signals. The sixth harmonic signals from the sixth harmonic detector showed an expected 6 times higher resolving power with (M + 3H)3+ charge state insulin ions as compared with that from fundamental signals from the dipole detector. Moreover, the insulin isotopic peaks with sixth harmonic frequency signals acquired with the sixth harmonic detector were resolved for a 40 ms data acquisition period but unresolved with the same duration dipole detector signals, corresponding to a 6-fold improvement in achievable spectral acquisition rates for a given resolving power.

Fabrication of porous titanium parts by powder bed fusion of Ti–TiH2 blended powder

When a high-energy laser is used to irradiate Ti–χTiH2 blended powder, hydrogen gas (H2) is generated by the decomposition of the titanium hydride (TiH2) powder and serves as a pore-former and active agent. In this study, the powder bed fusion (PBF) of Ti–χTiH2 (χ = 2, 5, 10 wt.%) blended powder was used to innovatively fabricate porous titanium parts. The trapped H2 in the rapidly solidified molten pool produces porosity in the deposited layer. The PBF test results showed that the beam interaction time to generate H2 through the decomposition of TiH2 is important in controlling the porosity formation. As the content of TiH2 increases, the porosity increases owing to the increased amount of H2 generated from TiH2. Additionally, the porosity increases with increasing scan rate. The faster the scan rate, the more H2 is trapped, because the rapidly solidified molten pool does not provide sufficient time for H2 to diffuse out. The variation in porosity with subsequent layering in the PBF process was also investigated. The results of this study show that the porosity can be actively controlled by adjusting the TiH2 mixing ratio (χ) and the laser-processing parameters.

Optimized Electrolytic Carbon and Electrolyte Systems for Electrochemical Capacitors

AbstractElectrochemical reduction of a molten Li2CO3−Na2CO3−K2CO3 eutectic is used to produce highly amorphous carbon with considerable oxygen functionalization in a process focusing on the conversion of CO2 to value‐added carbon. Electrochemical characterization of materials using multiple techniques in different electrolytes allowed for the optimization of these materials as electrochemical capacitor electrodes. Variation in capacitive performance of the investigated materials has been provided based on their physical characteristics. The synthesized carbons are hybrid materials, showing both pseudocapacitive and electric double layer contributions to the total performance. Annealing under nitrogen at 800 °C is shown to widen pores in the carbon material, resulting in an increase in medium scan rate (5–10 mV.s−1) capacitance. A stable specific capacitance of 425 F.g−1 is obtained at 5 mV s−1 in 0.5 M Na2SO4 after 1000 cycles.

Size Dependency of a ZnO Nanorod-Based Piezoelectric Nanogenerator Evaluated by Conductive Atomic Force Microscopy

ZnO nanorods are one of the most studied materials because it can be facilely grown on a wide range of substrates at low temperature. ZnO exhibits piezoelectricity as well as semiconducting properties, and hence is applicable to piezoelectric nanogenerators and sensors. In the present work, the effect of ZnO nanorods’ size on piezoelectric performance was systematically studied using conductive atomic force microscopy (C-AFM). We measured the total C-AFM signal for an observing area and evaluated the piezoelectric performance of the ZnO nanorods based on this total C-AFM signal. First, five samples of ZnO nanorod with distinct aspect ratios were hydrothermally grown on silicon substrates. Afterwards, two types of AFM tips with different spring constants were used to conduct C-AFM as a function of aspect ratio. When the AFM tip with a 42 N⁄m spring constant was used for the C-AFM measurement, the total C-AFM signal continuously increased with increasing aspect ratio. The total C-AFM signal increased with increasing normal force, but fluctuated with increasing scan rate. The results of the C-AFM experimental measurements were compared with the open-circuit voltage and short-circuit current of ZnO-nanorod based piezoelectric nanogenerator. We show that using C-AFM is a facile and effective method for investigating the optimized aspect ratio of ZnO nanorods for piezoelectric power generation. Key words: nanorod, zinc oxide, size effect, piezoelectric, conductive AFM, nanogenerator

Electrochemical and optical study of BiPO4 nanostructures for energy storage applications

In the present work, BiPO4 nanostructures were synthesized at via facile microwave technique. The structure and morphology of the synthesized sample were studied using an X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM) respectively. XRD analysis revealed monoclinic phase formation of BiPO4 nanostructures without any impurity peak and the average crystallite size calculated through Debye Scherrer’s formula is found to be 41 nm. FTIR and Raman spectroscopy also confirms the pure phase formation of BiPO4 nanostructures. SEM study shows the morphology of the synthesized sample and also confirms that synthesized material is in the nano-size range. The electrochemical properties of the as-prepared sample were studied by galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurement in a three-electrode system with 2 M KOH solution as an electrolyte. Specific capacitance is calculated from cyclic voltammetry and is found to be 309 Fg−1 at 2 mVs−1 which decreases by increasing scan rate from 2 mVs−1 to 35 mVs−1. Also, Specific capacitance is calculated from GCD and is found decrease from 268 Fg−1 to 171 Fg−1 as current density increases from 1 Ag−1 to 10 Ag−1. The investigation reveals that as-synthesized BiPO4 nanostructures can be utilized as an efficient electrode material for supercapacitor applications, providing sustainable and economic benefits.

Understanding the Basics of Electron Transfer and Cyclic Voltammetry of Potassium Ferricyanide - An Outer Sphere Heterogeneous Electrode Reaction

Understanding and controlling the processes occurring at electrode/electrolyte interface are very important in optimizing energy conversion devices. Cyclic voltammetry is a very sophisticated and accurate electroanalytical method enables us to explore the mechanism of such electrode reactions. In this work, electrochemical experiments using cyclic voltammetry were performed in aqueous KCl solution containing potassium ferricyanide, K3[Fe(CN)6] at a glassy carbon disc working electrode and the mechanism of the reactions is highlighted. The CV measurements shows that the ferricyanide [Fe(CN)6]3− reduction to ferrocyanide [Fe(CN)6]4− and the reverse oxidation process follows an outer sphere electrode reaction mechanism. Voltammetry analysis further indicates that the reaction is reversible and diffusion controlled one electron transfer electrochemical process. The peak currents due to [Fe(CN)6]4− oxidation and the peak current due to [Fe(CN)6]3− reduction increase with increase of concentration and scan rate increase. The diffusion co-efficient was determined by applying Randles-Sevcik equation. The report could be helpful for university students to understand the basics of electron transfer in redox processes and cyclic voltammetry.

Understanding the Basics of Electron Transfer and Cyclic Voltammetry of Potassium Ferricyanide - An Outer Sphere Heterogeneous Electrode Reaction

Understanding and controlling the processes occurring at electrode/electrolyte interface are very important in optimizing energy conversion devices. Cyclic voltammetry is a very sophisticated and accurate electroanalytical method enables us to explore the mechanism of such electrode reactions. In this work, electrochemical experiments using cyclic voltammetry were performed in aqueous KCl solution containing potassium ferricyanide, K3[Fe(CN)6] at a glassy carbon disc working electrode and the mechanism of the reactions is highlighted. The CV measurements shows that the ferricyanide [Fe(CN)6]3− reduction to ferrocyanide [Fe(CN)6]4− and the reverse oxidation process follows an outer sphere electrode reaction mechanism. Voltammetry analysis further indicates that the reaction is reversible and diffusion controlled one electron transfer electrochemical process. The peak currents due to [Fe(CN)6]4− oxidation and the peak current due to [Fe(CN)6]3− reduction increase with increase of concentration and scan rate increase. The diffusion co-efficient was determined by applying Randles-Sevcik equation. The report could be helpful for university students to understand the basics of electron transfer in redox processes and cyclic voltammetry.

Synthesis, crystal structures, photophysical, electrochemical studies, DFT and TD-DFT calculations and Hirshfeld analysis of new 2,2′:6′,2′′-terpyridine ligands with pendant 4′-(trimethoxyphenyl) groups and their homoleptic ruthenium complexes

[Ru(L1)2](PF6)2 (1) and [Ru(L2)2](PF6)2 (2): X-ray structures, CH⋯F/O, OH⋯F/N, CH⋯O/π, π⋯π interactions, absorption and emission spectra, DFT/TD-DFT, Hirshfeld analysis.

Electrochemical Sensors Modified with Combinations of Sulfur Containing Phthalocyanines and Capped Gold Nanoparticles: A Study of the Influence of the Nature of the Interaction between Sensing Materials.

Voltametric sensors formed by the combination of a sulfur-substituted zinc phthalocyanine (ZnPcRS) and gold nanoparticles capped with tetraoctylammonium bromide (AuNPtOcBr) have been developed. The influence of the nature of the interaction between both components in the response towards catechol has been evaluated. Electrodes modified with a mixture of nanoparticles and phthalocyanine (AuNPtOcBr/ZnPcRS) show an increase in the intensity of the peak associated with the reduction of catechol. Electrodes modified with a covalent adduct-both component are linked through a thioether bond-(AuNPtOcBr-S-ZnPcR), show an increase in the intensity of the oxidation peak. Voltammograms registered at increasing scan rates show that charge transfer coefficients are different in both types of electrodes confirming that the kinetics of the electrochemical reaction is influenced by the nature of the interaction between both electrocatalytic materials. The limits of detection attained are 0.9 × 10−6 mol∙L−1 for the electrode modified with the mixture AuNPtOcBr/ZnPcRS and 1.3 × 10−7 mol∙L−1 for the electrode modified with the covalent adduct AuNPtOcBr-S-ZnPcR. These results indicate that the establishment of covalent bonds between nanoparticles and phthalocyanines can be a good strategy to obtain sensors with enhanced performance, improving the charge transfer rate and the detection limits of voltammetric sensors.

Dislocation based stresses during electrochemical cycling and phase transformation in lithium-ion batteries

Lithium iron phosphate (LiFePO4) contains defects that play an important role in structural degradation of batteries. Linear defects called dislocations are introduced inside the lithium ion battery material during fabrication process accompanied by distortion produced stress fields around them. The present study deals with these mechanical stresses around dislocations in lithium iron phosphate and the change in stress field during phase transformation of lithium iron phosphate electrode material. A model consisting of multiple dislocations inside a lithium iron phosphate material incorporating anisotropic material properties is used to calculate stress fields using linear elastic theory and the superposition method. The stress fields around dislocations during phase transformation of lithium-iron phosphate are numerically calculated by incorporating the anisotropic properties of the material. The change in electrochemical behaviour of material due to change in stress field during phase transformation is also studied, where a modified electrochemical kinetics equation (i.e., Butler Volmer equation) is derived and used to account for dislocation induced stresses during the reversible cyclic voltammatery of the lithium iron phosphate. The results shows the stress inside material does not remain constant during phase transformation and its variations are dislocation orientation dependent. In addition, the result shows that the presence of stress fields around dislocations changes the electrochemical behaviour of the material as suggested by the shift in the cyclic voltammograms. The effect of increasing scan rate on cyclic voltammogram is also studied for lithium iron phosphate. The results show that the increase in current at peaks is independent of the orientation of dislocations studied. Moreover, the decrease in current corresponding to a particular overvoltage value before anodic peak and increase in current after the anodic peak is found to be somehow proportional to the scan rate. Increased scan rates show increased deviation of current from a cyclic voltammogram for material in which there is no phase transformation. The results provide an insight into how presence of defects and phase transformation changes the electrochemical behaviour of the material. It is concluded that the combined effect of the stresses induced around dislocations during phase transformation and high scan rate can be used for modifying battery materials for various applications by changing electrochemistry of electrodes. The present study incorporates electrochemistry, defects and phase transformation into one battery chemistry and thus is important in our understanding of the Li-ion batteries.

Synthesis of Polyaniline/Co(OH)2/Ni(OH)2 Nanocomposite Electrode Material for Supercapacitor Applications

We attempt to demonstrate the experimentally supercapacitive performance of polyaniline (PANI) - cobalt hydroxide (Co(OH)2)-nickel hydroxide (Ni(OH)2) nanocomposites (NCs), prepared potentiostically via electrochemical deposition, compared to phase pure individual nanostructures. Amorphous PANI, Co(OH)2 – Ni(OH)2 and NCs are entirely different from one another from the surface appearance point of view, PANI exhibits nanofiber morphology, NCs exhibits nanofiber partially covered with Co(OH)2 - Ni(OH)2 materials and Co(OH)2 - Ni(OH)2 shows platelet morphology. The electrochemical properties of the PANI, Co(OH)2 - Ni(OH)2 and HNs electrodes have been investigated by cyclic voltammograms and galvanostatic charge-discharge. The specific capacitances of PANI, NCs and Co(OH)2 – Ni(OH)2 are found to be 0.59, 50, 46.4, 85.7, 74.1 and 312.5 F/g, respectively, at a sweep rate of 10 mV/s in 1.0 M NaOH electrolyte. The same nature of retention values in area of CV curves and power densities of PANI, NCs and Co(OH)2 – Ni(OH)2 with increased in scan rates are 25.8, 70.5, 75.5, 76.6, 57 and 42.4%, respectively and the same nature of retention in charge density, specific capacitance, and energy density values are 38.7, 33.8, 40.7, 42.6, 23.1 and 17.3% respectively for PANI, NCs and Co(OH)2 - Ni(OH)2 electrodes with increase in scan rate.

Electro-Optically Active Polyaniline-Polypyrrole Double Layer Polymer Semiconducting Composite

Optically active polyanilines have been synthesized in the presence of chiral camphorsulfonic acid (CSA) by electrochemical polymerization in water medium. Polyaniline forms various electronic states such as emeraldine base, emeraldine salt, and pernigraniline. As prepared polyaniline in the presence of (+)-CSA is called as emeraldine salt. In this case, (+)-CSA shows two functions as 1) electro-dopant and 2) chiral inducer for the polyaniline, producing radical cation (polarons) and diction (bipolarons) as charge carriers and one-handed helically twist for the main chain. In the present research, we succeeded to obtain double layer conductive polymer film consisting of polyaniline and polypyrrole with electrochemical method. Fig. 1 shows the structure of the double layer polymer film. The optical activity of the polymer film was examined with optical rotatory dispersion (ORD). The double layer supports strength of the polymer film form. Electrical conductivity of the polymer film is ca. 0.25 S/cm evaluated with four-probe method. We carried out synthesis of a single layer polyaniline with (+)-CSA with potentiostat with three electrode system, Pt counter electrode saturated calomel electrode (SCE) as reference, and the polymer as working electrode. Fig.2 shows the results. Five scans afford to produce green polymer film deposited on the indium-tin oxide (ITO) coated grass electrode. The polymer shows redox activity conformed with cyclic voltammetry (CV). Increase of scan rate provides increase of current density in the electrochemical measurement because of increase of diffusion of ionic species in the electrolyte solution. The single layer polyaniline film displays electrochemical driven change in optical rotation evaluated with in-situ ORD/CV. The double layer polymer film was synthesized as followed. First, electrochemical polymerization of aniline as a monomer was carried out in concentrated optically active (+)-CSA with two electrode system. An application of electric filed (3.0 V) between electrodes in the electrolyte solution was carried out. The electrochemical polymerization reaction is rapidly progressed for formation of polymer thin film onto the anode side. Continuously, pyrrole as another kind of monomer was added to the electrolyte solution. The sequential electrochemical polymerization process affords to yield polypyrrole layer deposited onto the polyaniline layer. ORD measurement revealed that the double layer polymer film thus obtained is optically active. The bottom layer of polyaniline can be formed helical structure due to combination with optically active (+)-CSA. The top layer of polypyrrole may also form helical structure with aid of (+)-CSA as chiral doping agent. Chemical structure of the double layer polymer (composite) is examined with Fourie transform infrared optical absorption spectroscopy measurements. This result indicates that the polymer composite consists of polyaniline, polypyrrole, and CSA. The composite shows intense and wide range optical absorptions from invisible to infrared range due to delocalized charge carriers along the main-chain. The advantages of double conductive polymer film are redox activity, tunable optical activity, and color coordination. Top layer of polypyrrole is black in color with no polish and good redox character, and polyaniline as the bottom layer displays electro-optical activity. This paper reports convenient method for preparation of double layer system with electrochemical method. Further variation can be expected using different type of monomers for construction of multi-layer conductive polymer composite. This concept can be a first example as an electro-optically active conducting polymer composite. Figure 1

Glycine-assisted hydrothermal synthesis of NiCo2S4 as an active electrode material for supercapacitors

Nickel cobalt sulfide (NCS) was synthesized from nickel and cobalt nitrate (NCS-1) by a hydrothermal method. In another method, nickel cobalt sulfide (NCS-2) was also synthesized from hydrothermally synthesized nickel cobalt oxide (NCO). The syntheses of NCS-1 and NCO were conducted in the presence of glycine as a templating agent. The NCS and NCO samples were thoroughly characterized by different techniques. XRD studies showed that both NCO and NCS consisted of the cubic crystal phases. Cyclic voltammetry of NCO and NCS revealed that, with an increasing scan rate within the range of 10–100 mV s−1, the specific capacitance of the samples reduced. The specific capacitance of NCS-2, measured by galvanostatic charge–discharge, was found to be 675 F g−1, which is higher than those of NCO (313 F g−1) and NCS-1 (500 F g−1). The specific capacitance retention of NCS-2 was 88% over 1000 cycles, indicating the good cyclic stability of the material.