Bode Phase Plots Research Articles

Computer simulation of control contour of unmanned aviation complex to provide robustness and controllability

The article describes an approach to ensuring stability and controllability of unmanned aerial vehicle (UAV) with unknown aerodynamic characteristics by computer simulation of the airplane flight along a given route in the meteorological standard atmosphere. This computer model takes into account the programmed flight of an unmanned aerial vehicle in the meteorological atmosphere along a given route with waypoints. For this purpose the model incorporates 5 feedback systems (FS) with autopilot (AP) that ensure the stability and controllability of an airplane. Besides the autopilot and the airplane glider the control system encompasses the Kalman filter and a strapdown inertial navigation system. The appropriate structure and parameters of the control system of the model were chosen on the basis of practical technical solutions of the de veloped UAVs. The closed control systems of the model are developed according to the equations considering generation of aerodynamic forces and moments, a model of the standard atmosphere, the routing scheme and the feedback system with autopilot. The stability and controllability of the model were analyzed according to the theory of feedback systems with the graphic plotting of Bode magnitude plot and Bode phase plot. With a view to the assessment of dynamic and fluctuation errors of the control systems the model is represented by stochastic differential control system with the Kalman filter and the strapdown inertial navigation system in quaternions. The results of the computer simulation showed that the Kalman filter estimates the measured parameters with the noise reduction under 10 dB. The strapdown inertial navigation system influences the general dynamics of the control system during the assessment of its stability and controllability. Changing the band of the control system at the expense of external perturbations affecting the plane can lead to instability, and in order to avoid it the robust autopilot is recommended.

Improving photoelectric performance of MoS2 photoelectrodes by annealing

Semiconductor photoelectrochemistry (PEC) technology has attracted wide interest as it not only reveals the photoelectric properties of advanced materials, but also promotes energy conversion from the sunlight based on these materials. Herein, we investigated photoelectric properties of annealed and unannealed liquid phase exfoliated few-layer molybdenum disulfide (MoS2) photoelectrodes by PEC measurement. The linear sweep voltammograms and photoelectric response I-t curves demonstrate enhanced performance of MoS2 films after annealing. Nyquist impedance and Bode phase plots demonstrate a higher charge transfer property and a longer charge lifetime after annealing. The enhancement due to annealing could come from the increase of the crystalline and compact density of MoS2 nano-sheets, which is proved by X-ray diffraction and Raman spectroscopy in line with the absorption spectroscopy. Our results pave the way for the improvement of two-dimensional material based photoanodes for high performance of PEC applications by a simple method.

Topotactic Transformation of Solvated MgCr-LDH Nanosheets to Highly Efficient Porous MgO/MgCr2O4 Nanocomposite for Photocatalytic H2 Evolution.

The hybrid structure of nanoparticles (NPs) with nanosheets has the advantage of both anisotropic properties of NPs and large specific surface areas of nanosheets, which is desirable for many technological applications. In this study, MgCr2O4 spinel NPs decorated on highly porous MgO nanosheets forming MgO/MgCr2 O4( x) nanocomposites were synthesized by a one pot coprecipitation method followed by a heat treatment process of the solvated wet gel of MgCr-LDH with polar solvent N, N-dimethylformamide (DMF) at 400 °C. This novel synthetic methodology generates materials consisting of porous metal oxides nanosheets adhered with spinel phase NPs due to the slow generation of gases such as H2O, CO2, and NH3 under moderate temperature during the heat treatment process. The synergistic effect of much wider band gap MgO nanosheets and narrow band gap MgCr2O4 NPs added increased stability due to the stronger bonding coordination of MgCr2O4 NPs with MgO nanosheets. The obtained MgO/MgCr2 O4( x) nanocomposites possess large specific surface areas, highly porous structure, and excellent interface between MgCr2O4 NPs and MgO nanosheets, which proved from N2 sorption isotherm, TEM, HR-TEM study. With metallic ratio of MgCr3:1, MgO/MgCr2O4(MgCr3:1) nanocomposites exhibit highest H2 evolution rate of 840 μmolg-12h-1, which was 2 times higher than that of pure MgCr2O4(420 μmolg-12h-1). The LSV measurement study of MgO/MgCr2O4 (MgCr3:1) nanocomposite shows an enhancement of light current density of 0.22 μA/cm2 at potential bias of -1.1 V. The Mott-Schottky analysis suggested the band edge positions of the n-type constituents and formation of n-n type heterojunctions in MgO/MgCr2O4 (MgCr3:1) nanocomposite, which facilitates the flow of charge carriers. The EIS and Bode phase plot of MgO/MgCr2O4 (MgCr3:1) nanocomposite signifies the lower interfacial charge transfer resistance and higher lifetime of electrons (2.7 ms) for enhanced H2 production. Lastly, the enhanced photocatalytic H2 production activity and long-term stability of MgO/MgCr2O4(MgCr3:1) could be attributed to maximum specific surface area, porous structure, close intimacy contact angle between two cubic phases of MgCr2O4 NPs and MgO nanosheets, abundant oxygen vacancies sites, reduced charge transfer resistance and suitable band edge potential to drive the thermodynamic energy for H2 production. This work highlighted an effective strategy for the synthesis of cost-effective 2D porous heterojunctions nanocomposite photocatalyst for promising applications in the field of clean H2 production utilizing abundant solar energy.

Interfacial charge transport studies and fabrication of high performance DSSC with ethylene cored unsymmetrical dendrimers as quasi electrolytes

In this paper, authors focus the synthesis of conjugated unsymmetrical stilbenoid dendrimers by Heck and Horner-Wadsworth-Emmons coupling. In UV–visible absorption spectrum, the intensity of the absorption increases with increase in the generation of dendrimers. Further, bathochromic shift is observed on increasing the generation of the dendrimer from zero to first due to the greater widening of the energy gap between π-π* orbitals of the dendrimer system. Interfacial charge transport kinetics such as resistance, chemical capacitance and relaxation lifetime of the fabricated dye-sensitized solar cells (DSSC) are investigated using Nyquist and Bode phase plots by electrochemical impedance spectroscopy. Reduced electron relaxation lifetime (τe) of 1.83 ms (LiI + 7) and 1.04 ms (LiI + 8) provides efficient charge injection and thus reducing recombination process in the device. The performance of DSSC fabricated using unsymmetrical conjugated dendrimers with iodide electrolyte shows higher power conversion efficiency (PCE) than standard LiI based device. Two fold increments are achieved in PCE with first generation unsymmetrical dendrimers compared to their zeroth counterpart. The first generation unsymmetrical dendrimer 8 shows better PCE of 9.037% than all other synthesized dendrimers in the newly fabricated DSSC.

Fabrication of stable dye-sensitized solar cell with hydrothermally synthesized titanium dioxide nanorods as a photoanode material

TiO2 nanorods have been prepared by hydrothermal method at 170 °C for 24 h and successfully implemented in a stable solar cell as a photoanode material to replace the conventional nanoparticles which cause the recombination reactions at the interfaces due to a large number of grain boundaries. The synthesized products are characterized by powder X-ray diffraction, Raman and transmission electron microscopy analysis. The performance of the nanorods employed solar cell has been studied under the irradiance of 100 mW/cm2. The fabricated device showed a power conversion efficiency of 5.42%. The open-circuit voltage, short-circuit current density and fill factor of the device are 0.647 V, 13.64 mA/cm2, and 61.5%, respectively. The electrochemical behavior of the fabricated device has been analyzed with electrochemical impedance spectroscopy. The lifetime of the injected electrons in the photoanode network has been found to be 10 ms, which was evaluated from Bode phase plot. From the Nyquist plot of the impedance spectrum, lower charge transfer resistance (Rct) has been observed at the TiO2/dye/electrolyte interface. The sealed device was monitored frequently with 500 h of the interval. Up to 2500 h, no significant drop has been observed in the J–V characteristics.

Enhanced photocatalytic activity with a heterojunction between BiVO4 and BiOI

One of the current key issues in the photocatalysis is to obtain the band alignment of coupled semiconductor experimentally, which is the most significant aspect for understanding the efficient photocatalytic activity precisely. In this article, a BiVO4/BiOI{001} heterojunction was detected by the transmission electron microscopy (TEM). The results of electrochemical impedance spectroscopy (EIS) reveal that a higher efficiency of charge immigration across the electrode/electrolyte interface for the BiVO4/BiOI{001}. In addition, the electron lifetime was investigated by the Bode phase plots, which are responsible for the observed photocatalytic behaviors. As a result, the photocatalytic activities for rhodamine B (RhB) degradation and iodine ion oxidation are remarkably increased compared to the individual BiVO4 and BiOI{001}. In fact, a direct band alignment in the BiVO4/BiOI{001} does not give well a logical interpreting on its photocatalytic behavior. However, through the valence-band offset formula, we demonstrated the exact band alignment of corresponding components in the BiVO4/BiOI{001}. This band alignment was further confirmed by the PL spectra, which CM2 with photo-oxidation (Mn2+) is red shift and CM2 with photo-reduction (Ag+) is blue shift compared with CM2.

New Calibration Technique of Contact-less Resonant Biosensor

This paper addresses the problem of calibrating magnetically-coupled passive sensors for medical applications. We developed an analytical model of such sensor including the impact of some disturbances (distance and angle between antennas). This model is valid for sensors with different dimensions of antennas. Thanks to this model, the ideal indicator of the disturbances for calibration can be identified. It has been applied to the case study of Intra-Ocular Pressure (IOP) sensor. A new indicator (the slope of the baseline of the Bode phase plot) has been chosen.This new indicator is reliable to significant distance and angle variations between primary and secondary.

Structural stability of poly(3-methylthiophene) and poly(3,4-ethylenedioxythiophene) in the ITO/PEDOT:PSS/P3MT system

With the aim of understanding the factors that enhance the efficiency of Organic photovoltaic cells (OPVs), poly(3-methylthiophene) (P3MT) was anodically deposited (+1.65 V vs Ag/AgCl) on ITO coated with poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (ITO/PEDOT:PSS) in LiClO4-ACN. This active layer was studied by ex situ Raman spectroscopy as a function of time, and led us to the conclusion that the radical cation species in the P3MT thiophene ring was very stable compared the ITO/P3MT system. Bearing in mind that P3MT synthesis on ITO/PEDOT:PSS occurs at high anodic potential, the behavior of the PEDOT at the applied potential was verified by electrochemical impedance spectroscopy and in situ Raman spectroscopy of the PEDOT:PSS on Pt. The Bode phase plots at potentials of −0.60, 0.00, 0.40, 0.60 and 0.80 V for the Pt/PEDOT:PSS/LiClO4-ACN system showed the contributions of the polaron and bipolaron conduction of the PEDOT thiophene ring. To back up this study, in situ Raman spectroscopy was used at the same potentials to verify the characteristic frequencies of the radical cation and dication species of the PEDOT thiophene ring. These results provided a basis for determining that the radical cation form of the PEDOT thiophene ring was the same stable form at the PEDOT:PSS/P3MT interface, which could enhance charge injection processes in OPVs.

Simultaneous Compensation of the Gain, Phase, and Phase-Slope

This paper deals with the problem of simultaneous compensation of the gain, phase, and phase-slope at an arbitrary frequency by using a fractional-order lead/lag compensator. The necessary and sufficient conditions for feasibility of the problem are derived. Also, the number of existing solutions (i.e., the number of distinct fractional-order lead/lag compensators satisfying the considered compensation requirements) is analytically found. Moreover, as a sample application, it is shown that the obtained results for the considered compensation problem are helpful in tuning fractional-order lead/lag compensators for simultaneously achieving desired phase margin, desired gain cross frequency, and flatness of the Bode phase plot of the loop transfer function at this frequency.

Corrosion inhibition studies of cigarette waste on the iron surface in acid medium: electrochemical and surface morphology analysis

Purpose The purpose of this paper is to study the corrosion inhibition tendency of cigarette waste (water extracts of cigarette butts, WECB) on an iron surface in an acid medium. Design/methodology/approach The electrochemical impedance spectroscopy and polarization techniques were used to analyze the performance of WECB on the iron working electrode. Electrochemical polarization curves were used to determine the intensity of the metal corrosion, specifically to see the effectiveness of the anodic and cathodic reactions in the corrosive medium having WECB. Moreover, the electrochemical impedance of WECB with electrode was analyzed qualitatively. The electrochemical data that relate isotherm adsorption of WECB with iron were analyzed; furthermore, the scanning electron microscope was used to analyze morphology change during the corrosion inhibition. Findings After analyzing the impedance data, it is seen that there exists a single capacitive semicircle at the higher frequency range corresponding to a one-time constant in the Bode-phase plot. In the polarization curves studies (Tafel slopes), the current densities of both cathodic and anodic branches are greatly affected in the presence of WECB in the corrosive medium, suggesting that WECB performs as a mixed inhibitor. The free energy data and Temkin adsorption isotherm process show that the adsorption process of WECB on the metal surface follows a physisorption. Furthermore, the WECB-coated metal surface analyzed by scanning electron microscopy confirms the corrosion inhibition of WECB in the acid medium. Research limitations/implications An in-depth characterization of the corroded scales is recommended to endorse the results of this study. Social implications There may be some people who may challenge that the research may encourage smoking; however, if taken positively, the research offers a very cost-effective and eco-friendly solution to tackle the cigarette waste. Originality/value Idea of the present work is to reuse the WECB as corrosion inhibitors for the metal surface, as this waste contains large amount of nicotine, which exhibits corrosion inhibition properties. The present work deals with the study of corrosion inhibition properties of WECB on the iron surface in acid medium. The findings of this study can be very useful from scientific, as well as industrial application point of view. Moreover, the research is important as there is no proper recycling process for this waste so as to maintain a clean environment.

Silicotungustic acid incorporated gel polymer electrolyte as efficient redox mediator for dye sensitized solar cells

Silicotungustic acid (STA) modified gel polymer electrolytes (GPEs) with various wt% (0–5%) were prepared using Poly(ethylene oxide) as polymer and LiI/I2 as redox couple. The conformational changes, by the addition of STA were studied using Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy. Electrochemical properties like ionic conductivity (σ) and tri-iodide diffusion co-efficient (DI3−) were studied using electrochemical impendence spectroscopy and linear sweep voltammetry experiments respectively. Photovoltaic properties of fabricated dye sensitized solar cells (DSSC) using such electrolytes were studied under 85mWcm−2 illumination and the results were supported by Nyquist and bode phase plots from electrochemical impendence spectroscopy. A photovoltaic conversion efficiency of 6.26% was achieved for the GPE containing 3wt% STA. Finally, the effect of LiI blocking layer for the DSSCs containing STA free and STA modified gel electrolytes was studied.

Electrochemical copolymerization of acrylic acid and acrylamide on the carbon fiber surface

Electrochemical polymerization of acrylic acid and acrylamide on carbon fiber was carried out by using cyclic voltammogram in the presence of sulfuric acid (H2SO4) as electrolyte. Cycles, monomer mass ratio, scan rate, and H2SO4concentration had an effect on the electropolymerization, and electrochemical impedance spectroscopic behavior of modified carbon fiber was studied. Systematic experiments were conducted to determine the tensile strength of carbon fiber/epoxy resin composites before and after modification. As a result, the tensile strength of modified carbon fiber/epoxy resin composites was improved greatly. Surface morphology of the polymer films on carbon fiber was investigated by using scanning electron microscopy. It was found that voltammograms of electrodes prepared showed irreversible oxidation–reduction of the polymer films and capacitive behaviors of coated carbon fiber were defined using Nyquist plots, Bode magnitude plot and Bode phase plot at low-frequency region.

In-Operando Observation of Geometrical-Site-Dependent Activity of Spinel Co3O4 for Water Oxidation

Spinel Co3O4, comprising one Co2+ ion in the tetrahedral site (Co2+ Td) and the other two Co3+ ions in the octahedral site (Co3+ Oh), has been widely explored as promising oxygen evoltuion reaction (OER) catalyst, and several research works have proposed that the electrochemical OER performance of spinel Co3O4 is geometry site dependent. However, without any conclusive evidence, the roles of two geometrical cobalt ions, expecially under applied bias, have remained elusive. Here, we investigate the geometrical-site-dependent OER activity of Co3O4 by substituting Co2+ Td and Co3+ Oh with inactive Zn2+ and Al3+, respectively. Following a thorough in-operando analysis by electrochemical impedance spectroscopy (EIS) and X-ray absorption spectroscopy (XAS), our results indicate Co2+ Td and Co3+ Oh differ from each other in surface-kinetics and electrochemical reactivity towards OER, and more importantly, Co2+ Td is the vital species in Co3O4 for electrochemical water oxidation. We use a simple ion-substitution strategy to individually study the role of Co2+ Td and Co3+ Oh for OER, and our results indicate Co3+ Oh predominated catalyst performs a poor activity, yet Co2+ Td predominated catalyst still performs well. The OER activities of pristine and substituted cobalt oxides were first evaluated by cyclic voltammetry (CV) and linear scanning voltammetry (LSV) with corresponding calculated Tofel slope. Surface kinetic properties of OER can be revealed by the Tofel plots obtained from the normalized polarization curves. The general OER mechanism in alkaline solution on the metal site starts with a proton-coupled electron transfer from a surface-bound aquo species followed by an O-O bond formation. Among different samples tested, ZnCo2O4 shows a Tafel slope of 113 mV/dec, indicating that the OER process in ZnCo2O4 is rate-limited at the first stage where the surface of catalyst is strongly bonded with –OH groups (reaction order = 1 with respect to OH– species with featured Tafel slope of 120 mV/dec). The Tafel slope for CoAl2O4 (~56 mV/dec) and Co3O4 (~69 mV/dec) are much smaller than that for ZnCo2O4 and close to a featured Tafel slope of 60 mV/dec, suggesting a different rate-determining step. The OER reactions of CoAl2O4 and Co3O4 are controlled by the equilibrium state between the –OH adsorption and O-O formation in an intermediate coverage regime of –OH groups on the active sites. Due to the fact that the chemical environment of Co3O4 is dynamically changeable during electrocatalysis with applied bias, to gain in-depth information of underlying controlling factors for water oxidation, in-operando EIS analysis is applied here to gain in-depth information of underlying controlling factors. The Bode phase plots generalized from in-operando EIS reveal Co3+ Oh in Co3O4 is responsible for surface DLC, while Co2+ Td is responsible for main water oxidation reaction as an non-homogeneous charge distribution caused by surface oxidized species (e.g., Co3+→ Co4+) is observed on the low frequency range. This finding is identical to the two featured Tafel slopes, 120 mV/dec and 60 mV/dec, in terms of two different surface kinetics as revealed on Co3+ Oh predominated catalyst and Co2+ Td predominated catalyst, respectively. To further probe the real-time variation of chemical environment on the catalyst during OER, In-operando XAS is carried out in a home-made in-operando cell. It is revealed Co2+ Td with initially low oxidation state is able to release electrons under applied bias, which facilitates the interaction with oxygen intermediates on the catalyst surface. Meanwhile, the interatomic distance between center Cobalt and oxygen is greadaully reduced as indicatd in our K-edge EXAFS spectra for Co2+ Td predominated Sample (CoAl2O4), while, we can not observe such kind of variation for Co3+ Oh predominated Sample (ZnCo2O4). This electron-releasing and oxygen-adopting process on Co2+ Td predominated CoAl2O4 suggests the formation of cobalt oxyhydroxide (CoOOH) can takes please with the assistant from the oxidation process of Co2+Td, which acts as the main active species for water oxidation on Co3O4. With using the exquisite ion-substitution approach and in-operando analysis, the role of Co2+ Td and Co3+ Oh in spinel Co3O4 during electrochemical oxygen evolution reaction can be individually indentified. Our work highlights the vital role of Co2+ Td for Co3O4 toward water oxidation especially under applied bias, and emphasizes the importance of in-operando investigations on electrocatalysis for instantaneously probing the real-time electrochemical kinetics and surface reactions. Figure 1

Probing Order Phenomena and Interactions in Molten Salt Binary Mixtures with Impedance Spectroscopy and Cyclic Voltammetry

Temperature-dependent electrochemical impedance spectroscopy and cyclic voltammetry are employed to study changes in the order and interactions in molten alkali-halide salt binary-mixtures. Nyquist plots of KCl-LiCl, KCl-NaCl and KBr-NaBr equimolar mixtures at 700°C are characterized by a small semicircle at high-frequencies and a larger low-frequencies semicircle. Two peaks with well-separated time constants are present in the Bode phase plots. Those are referred to the interfacial and double-layer properties at high frequencies and to the bulk electrical properties away from the electrode at low frequencies. Along the measured temperatures (700–800°C), the KCl-NaCl mixture is featured with a low-frequencies peak only below ∼750°C, which diminishes at higher temperatures, as may point on a dispersion of the ionic structure. The entropies of the mixtures are calculated from the change of the electrochemical windows with temperature. The entropy of KCl-NaCl increases drastically along heating, implying on a drastic change in the order and interactions in the melt. In contrast, the KX-LiX (X = Cl, Br, I) entropies do not change. It is suggested that the stability of the ionic structure of the molten salt mixtures with temperature is a result of collaborative asymmetric polarization interactions among the different ions in the melt.

Characterization of the photoelectron behavior of working electrodes modified with a titanium-dioxide window layer in dye-sensitized solar cells

Titanium dioxide (TiO2) is currently used as a working electrode in dye-sensitized solar cells (DSSCs). The conventional working electrode is comprised of an absorption layer (with a TiO2 particle size of ~20 nm) and a scattering layer (with a TiO2 particle size of ~300 nm) on a fluorinedoped tin-oxide (FTO) substrate. In this study, we inserted a window layer with a 10-nm TiO2 particle size between the FTO substrate and the absorption layer in order to increase both the transmittance and the specific surface area of the TiO2. Electrochemical impedance spectroscopic analysis was conducted to characterize the electronic behavior of the working electrode. The Bode phase plot and the Nyquist plot were interpreted to determine the impact of the insertion of the window layer on the internal resistance of the DSSC and on the carrier lifetime. The photocurrent from the cell increased due to an increase in the specific surface area, which was a result of the addition of the window layer with a smaller particle size (10 nm). Further, the insertion of the window layer in the working electrode was found to lead to an effective increase in the transmission of the incident light. Therefore, The insertion of the window layer it was concluded to contribute to an increased conversion efficiency in the DSSCs.

Characterization of the interaction between P3ATs with PCBM on ITO using in situ Raman spectroscopy and electrochemical impedance spectroscopy

In this study, phenyl-C61-butyric acid methyl ester (PCBM) was deposited onto indium tin oxide (ITO) using the Langmuir–Schaefer technique, and poly(3-methylthiophene) (P3MT) and poly(3-hexylthiophene) (P3HT) were then electrochemically synthesized onto the ITO/PCBM, producing PCBM/P3MT and PCBM/P3HT films respectively. These films are widely used to create heterojunctions in organic photovoltaic cells, and they were produced in this study in order to monitor the charge transfer process between the P3ATs and PCBM. Cyclic voltammetry (CV) of the ITO/PCBM/P3AT systems demonstrates dislocation of oxidation and reduction peaks and a variation in the current of these peaks in relation to those observed in ITO/P3ATs. Charge transfer resistance (RCT) were determined using electrochemical impedance spectroscopy (EIS) to produce Nyquist plots at open circuit potential and at different applied potentials. ITO/PCBM/P3HT had a lower RCT value than ITO/P3HT and ITO/PCBM/P3MT. Bode phase plots produced using EIS indicated that the charge transfer process in ITO/PCBM/P3HT is associated with polaron conduction (radical cation) and in ITO/PCBM/P3MT with bipolar conduction (dication). This study of the behaviour observed in these systems using CV and EIS techniques was supplemented with ex situ and in situ Raman spectroscopy. Structural variations were observed in segments of the P3HT polymer chain when interacting with PCBM in the ITO/PCBM/P3HT system, but not for ITO/P3MT in the ITO/PCBM/P3MT system. The charge transfer observed between PCBM and P3HT was associated with the stabilization of the radical cation species found in P3HT in this material.

A New Method for Getting Rational Approximation for Fractional Order Differintegrals

AbstractIn this paper a new algorithm is presented to calculate the poles and zeros to approximate a fractional order (FO) differintegral (s±α,α∈(0,1)) by a rational function on a finite frequency band ω∈(ωl,ωh). The constant phase property of the FO differintegral is the basis for development of the algorithm. Interlacing of real poles and zeros is used to achieve the constant phase. The calculations are done using the asymptotic Bode phase plot. A brief investigation is made to get a good approximation for the Bode phase plot. Two design parameters are introduced to keep the average phase close to the desired phase angle and to keep the error within the allowed bounds. A study is done to empirically understand the relationship between the error and the design parameters. The results thus obtained help in the further calculations. The algorithm is computationally simple and inexpensive, and gives a fairly good approximation of fractance frequency response on the specified frequency band.

Synthesis of methyl 4-(9H-carbazole-9-carbanothioylthio) benzoate: electropolymerization and impedimetric study

Methyl 4-((9H-(carbazole-9-carbanothioylthio) benzoate (MCzCTB) was chemically synthesized and charac- terized by FTIR, 1 H NMR, and 13 C NMR. A novel synthesized monomer was electropolymerized on a glassy carbon electrode (GCE) in various initial molar concentrations of (MCzCTB)0= 1, 3, 5, and 10 mM in 0.1 M NaClO4/CH3CN and 1 M H2SO4. P(MCzCTB)/GCE was characterized by cyclic voltammetry, Fourier transform infrared-attenuated transmittance reectance, scanning electron microscopy-energy dispersive X-ray, and electrochemical impedance spec- troscopy. The capacitive behavior of the modied electrode was obtained by Nyquist, Bode-magnitude, and Bode-phase plots. The highest capacitance at low frequency was obtained as � 53.1 mF cm 2 from Nyquist plot and 19.454 Fg 1 at a scan rate of 10 mV s 1 for (MCzCTB)0 = 1.0 mM. CS2 and OCH3 groups are electron-withdrawing and electron- donating groups in the monomer structure. These groups aect the polymerization and capacitive behavior of the polymer. The polymer may be used for supercapacitor and biosensor applications in the future.

Supercapacitor Behavior of Poly(Carbazole-EDOT) Derivatives/Multi-Walled Carbon Nanotubes, Characterizations and Equivalent Circuit Model Evaluations

Three new different comonomers of carbazole-EDOT derivatives had been previously synthesized and characterized in detail. In this study, electroactive materials were electropolymerized onto multi-walled carbon nanotube (MWCNT) modified glassy carbon (GC) electrode in 0.1 M sodium dodecyl sulphate (SDS) solution. The electrochemical impedance spectroscopic results of Nyquist, and Bode-magnitude and Bode-phase plots show that polymers/MWCNT composites possess good capacitive characteristics. P(Com2)/MWCNT/GCE system's specific capacitance was up to Sc = 132.6 F g−1 at the scan rate of 70 mV s−1 from the area formula, Eq. (1). Furthermore, P(Com2)/MWCNT composite had very rapid charge/discharge ability with specific capacitance of Sc = 75.23 F g−1 at DC potential of 0.3 V from Nyquist plot, and Sc = 90.53 F g−1 at the scan rate of 60 mVs−1 from charge formula, Eq. (2), which is important practical advantage. In addition, such composite had a good cycling performance and a wide potential window. Long-term stability of the capacitor was also tested by CV, and the results indicated that, after 500 cycles, the specific capacitance was still at ∼100.0%, ∼89%, and ∼97.0% of the initial capacitance for P(Com1)/MWCNT, P(Com2)/MWCNT, and P(Com3)/MWCNT, respectively. An equivalent circuit model of Rs(C1(R1(Q(R2W))))(CGCRGC) was obtained to fit the experimental and theoretical data. Solution resistance (Rs) and resistance from GCE decrease gradually. However, capacitance of film (C1), constant phase element (Q), and n values increase for P(Com1), P(Com2), and P(Com3)/MWCNT, respectively. Therefore, more homogeneous and less rough surface composite film was obtained by addition of MWCNT in the composite material.

Evaluation of Back Contact in Spray Deposited SnS Thin Film Solar Cells by Impedance Analysis

The role of back metal (M) contact in sprayed SnS thin film solar cells with a configuration Glass/F:SnO2/In2S3/SnS/M (M = Graphite, Cu, Mo, and Ni) was analyzed and discussed in the present study. Impedance spectroscopy was employed by incorporating constant phase elements (CPE) in the equivalent circuit to investigate the degree of inhomogeneity associated with the heterojunction and M/SnS interfaces. A best fit to Nyquist plot revealed a CPE exponent close to unity for thermally evaporated Cu, making it an ideal back contact. The Bode phase plot also exhibited a higher degree of disorders associated with other M/SnS interfaces. The evaluation scheme is useful for other emerging solar cells developed from low cost processing schemes like spray deposition, spin coating, slurry casting, electrodeposition, etc.