Electro-active Regions Research Articles

Integration of vanadium diphosphide with 2D cobalt phosphide architected as an extensible redox active positrode for alkaline supercapacitor

Metal phosphides in the form of rationally constructed two-dimensional (2D) nanosheets hold significant promise as versatile materials for energy storage applications. This study introduces a novel hybrid supercapacitor electrode, composed of a binder-free vanadium phosphide integrated cobalt phosphide (VP@CP) on a nickel foam substrate. The fabrication process involves the hydrothermal growth of Co2(OH)2BDC (BDC- 1,4-benzenedicarboxylate) nanosheets on a Ni-foam substrate (CMF-Ni), followed by the deposition of VO2 on CMF nanosheets (VO@CMF-Ni) using chronoamperometry and phosphorization of the VO@CMF-Ni to yield VP@CP-Ni nanosheets. Particularly, the density functional theory (DFT) results show that the VP2 integrated Co2P sample provides metallic behavior and low adsorption energy of OH− ions, resulting in improved electrochemical redox process. These bimetallic phosphides exhibit outstanding properties, including enhanced pathways for rapid ion transport and storage, increased electronic conductivity, and expanded electroactive regions facilitating the faradaic charge storage process. Due to the presence of vanadium and cobalt coupled sites, the fabricated VP@CP-Ni electrode was able to attain a maximum areal capacity (CAR) of 971 mA h cm−2 at 6 mA cm−2. Additionally, the fabricated hybrid device (HDC) exhibits an impressive specific energy (SE) of 30.9 Wh kg−1 at a specific power (SP) of 1344 W kg−1, and excellent cyclic durability. These remarkable results stimulate the exploration of such possible 2D VP@CP-Ni nanosheets with promising charge storage electrode capabilities to develop a future era of energy storage devices.

Rietveld refined structural, optical and temperature dependent impedance spectroscopy of NiO–ZnO heterostructure composite: Synthesized through solid state method for high-frequency devices

Multifunctional NiO–ZnO heterostructure composite powder is economically synthesized through a solid-state route having a crystallite size of 23 (±2) nm. Chemical composition is identified through FTIR, the peak associated with Zn–O is detected at 1049 cm−1. However, the peaks detected at 870 cm−1 and 590 cm−1 show Ni–O stretching vibrations. UV-DRS technique is employed to estimate the energy band gap (Eg) around 3.18 eV. The impedance studies confirmed the presence of a non-Debye-type relaxation mechanism, electrical parameters confirm the contribution of electroactive regions i.e. grains and interfaces. An equivalent circuit model (R-CPE) is employed to measure various electrical parameters. Adiabatic small polaron hopping model is applied to estimate activation energies for Ni+2 (0.30 eV), Zn+2 (0.35 eV), and bulk (0.32 eV) respectively. The hopping length at the interface is estimated at around 0.8 Å by employing Mott's variable range hopping model. Jonscher's power law (JPL) is used to fit ac conductivity data, and conclude activation energy around 0.3 eV. The conduction mechanism through the whole frequency range (1–107 Hz) is governed by correlated barrier hopping. Various physical parameters i.e. binding energy (Wm), hopping length, and barrier height compared throughout the whole temperature range (313–393 K). The rate of increase in real permittivity at low frequency is related to the disorder of the cation at sublattices. These results deduced potential for NiO–ZnO heterostructure composite for high dielectric permittivity with low tangent loss for high energy storage applications.

Understanding the transport properties of perovskite compounds as a function of temperature, frequency and DC-bias voltage using experimental measurements and appropriate theoretical models.

The present paper provides interesting measurements and methodologies to investigate the key factors controlling the electrical response of perovskite systems. The studied system was successfully prepared using a solid-state route. The chemical analysis and the X-ray diffraction results confirm the formation of the desired perovskite phase. As a result, the DC-resistivity analysis shows that the transport properties are governed by hopping mechanisms above the transition temperature. In this case, thermal agitation allows the charge-carriers to hop across the insulating barrier in the form of grain boundaries. Then, the dominance of the grain boundary contribution is proved. AC-resistivity spectra are investigated in terms of numerous power laws (UDR, SPL and NCL). Accordingly, the decrease in the resistivity values at high frequencies is explained through hopping and tunneling processes. Indeed, it is proved that the electrical transport phenomena are governed by QMT and CBH models. The coexistence of direct (C-C) and indirect (C-A-C) interactions explains the multi-behavior of the AC-resistivity. The scaling representation displays a single muster curve describing the universal dynamic response (UDR). Thus, it reveals the universality of the electrical resistivity of the system. However, the double Schottky barrier model is used to explain the grain boundary effects. A critical frequency "νc" is detected under temperature and DC-bias voltage effects. These observations disclose, in a different way, the separate contributions of the electro-active regions of the sample in the conduction phenomenon.

Tailoring frequency/temperature independent colossal dielectric constant in Zn-doped Fe3O4/Fe2O3@C/PANI using phase co-existence approach

Introducing doped binary oxides to polymers offers a promising way towards advancement of charge density/energy storage materials with colossal dielectric constant. However, the origin of colossal dielectric constant explored in terms of conduction mechanism with a deeper understanding of the coexistence of phases/interfaces in these materials still requires much attention. In this context, we synthesised Zn-doped Fe3O4/Fe2O3@C/PANI composite that exhibits frequency and temperature independent colossal dielectric constant over a broad range, 1 Hz to 10 MHz and 93 K to 333 K, respectively. We analyzed the impedance data using an equivalent circuit model and Cole-Cole fitting to gain insight into the colossal dielectric response and low dielectric loss. The relaxation phenomenon corresponding to a highly stable electroactive region is validated by the distribution of relaxation time (DRT). Furthermore, the composite exhibited a non-relaxor-like behavior due to diffuse phase transition near semiconductor-to-metallic transition (SMT), observed at 303 K. The charge carriers follow the variable range hopping (VRH) and Arrhenius models yielding localization length of 3 Å and activation energy of 35 meV, which supports the charge transport mechanism between like cation interfaces. This detailed analysis covering the frequency and temperature independent dielectric constant along with the understanding of relaxation and conduction phenomena could provide a viable approach towards producing charge density/energy storage devices for practical applications.

Temperature-dependent conduction mechanism of NiO@Carbon@Polypyrrole nanomaterial with EMI shielding characteristics

A simple hydrothermal technique and in-situ chemical oxidative polymerization of pyrrole monomer yield the functionalized NiO@C@PPy nanomaterial for electromagnetic shielding applications. The crystal structure, morphology, dielectric and electromagnetic shielding (EMI) performance in the X-band (8.2–12.4 GHz) is thoroughly studied. Impedance spectroscopy is utilized to study the electrical response of a NiO@C@PPy pellet. This study focuses on the modulations of relaxation time with frequency at different temperatures. In the NiO@C@PPy composite, a semiconductor-to-metal transition (SMT) is observed, at 328 K. The conduction mechanism of NiO@C@PPy is explained based on the carrier hopping transport model in Ni2+ and Ni3+ ions. It is evident from the activation energy value (Ea ≈ 0.32 eV) determined from impedance, conductivity, and dielectric data that the relaxation and conduction processes correspond to the same electro-active region. Using the variable range hopping (VRH) model localization length of the carrier is calculated to be 1.56 Å. The NiO@C@PPy sample demonstrated enhanced conductivity and low dielectric values which are vital in EMI shielding applications. Consequently, the electromagnetic interference shielding effectiveness is found to be 21.9 dB of NiO@C@PPy in the X-band frequency range. This composite material is a good candidate for high frequency shielding applications.

Machine Learning Across Metal and Carbon Support for the Screening of Efficient Atomic Catalysts Toward CO2 Reduction

AbstractDeveloping efficient atomic catalysts (ACs) for the CO2 reduction reaction (CO2RR) still requires ultrahigh experimental resources and a long research period due to the complicated reaction mechanisms and abundant active sites. Herein, this work presents the energy‐based first principles machine learning (FPML) method for the first time based on over 15 000 datasets to directly predict the reaction trends of the CO2RR. The unique scaling relationship of the hydrogenation steps is revealed in ACs for the CO2RR, which is correlated with the active sites instead ofelectron transfer numbers. Based on machine learning (ML) predictions, this work reports that the standard electrode potential is affected by the pH values, and proposes a zero‐point calibration strategy to realize more accurate predictions of electrocatalysis reactions to supply meaningful references to experiments. The formation of electroactive regions constructed by mixing active sites is revealed, which confirms the neighboring effects for the activation of active sites. In addition, the prediction of C3 intermediates indicates the potential of multicarbon coupling processes on the carbon active sites of graphdiyne. This work supplies an effective method to predict chemical reaction trends of different ACs in the CO2RR by ML, which is expected to accelerate the rational design of novel ACs for broad electrocatalysis.

Co-electrodeposited poly (3, 4-ethylenedioxythiophene) (PEDOT)-multiwall carbon nanotubes (MWCNT) hybrid electrodes based solid-state supercapacitors using ionic liquid gel electrolyte for energy storage with pulsed power capabilities

Electrochemical and energy storage properties of poly(styrene sulfonate) doped poly (3, 4-ethylenedioxythiophene) (PEDOT:PSS) conducting polymer hybridized with the multiwall carbon nanotubes (MWCNT) are studied as solid-state supercapacitor with anion-doped ionic liquid (IL) gel electrolyte. The PEDOT: PSS-MWCNT composite electrodes were formed by co-electrodeposition using sequential 4 mA cm−2 current density with 10 ms current pulses in an aqueous medium with highly dispersed MWCNTs using Na-dodecyl sulfate (SDS) surfactant, PSS dopant (10–20 %) and EDOT monomer. Raman spectral study confirms with ≤10%PSS, the MWCNTs are moored into PEDOT chains via covalent bonding with carbons at α and β-position as PEDOT grows over flexible graphite substrate. Specific capacitance of 138 F g−1 discerned from cyclic voltammetry in IL-gel electrolyte is higher than reported in liquid electrolytes and chemically polymerized electrodes. Electrical double layer (EDL) capacitance analysis shows high 71.2 mF cm−2 contribution originated from MWCNTs with 10 % PSS, and slightly lower 48.8 mF cm−2 with 20 % PSS. The performance optimized PEDOT: PSS (10 %)- MWCNT (1 mg) based supercapacitors show large (43 %) access to the electroactive nanoporous surface regions contributing to capacitive charge and 57 % electrode has access to charge storage via diffusion limited Faradaic process. Nyquist plots analyzed for Warburg coefficient show minimal charge transfer resistance unimpacted by ionic diffusion. From the frequency response of the real and imaginary impedances pulsed power is assessed as 6.33 kW kg−1 at energy density 3.43 Wh kg−1. Charge-discharge behavior of optimized supercapacitor over 0.05–2.0 A g−1 current densities is triangular, highly symmetrical. Ragone plot shows high energy density of 7.7 Wh kg−1 at specific power 5.3 kW kg−1 plateauing out to 4.4 Wh kg−1 at higher specific power of 11.5 kW kg−1. Charge-discharge cycle analysis shows merely 20 % loss of specific capacitance by ∼500 cycles largely stabilizing for over 2000 cycles while the Coulomb efficiency remaining invariant at 95 %.

Construction of Z-scheme MnCo2O4/Sn3O4 heterostructured photoanodes with enhanced photoelectrocatalytic degradation of reactive brilliant blue KN-R

Rapid and efficient handling of the printing and dyeing wastewater benefits environmental conservation. Photoelectrocatalysis (PEC) technology is a novel method used to mineralize large molecules of non-degradable organic dye molecules in water completely into small molecules in recent years. By generating intermediate reactive species (e.g., superoxide radicals and hydroxyl radicals) during the processing, the products of PEC technology are cleaner and pollution-free, making it a desirable environment-friendly approach. In this work, a composite semiconductor material with Z-Scheme heterostructure was constructed as a photoanode to promote the generation of intermediate reactive radicals for the efficient degradation of organic dyestuff wastewater. A series of composite materials with Sn3O4 nanosheets decorated spinel-type MnCo2O4 nanorods were synthesized through a simple two-step hydrothermal process on the titanium metal substrate. The degradation reaction cell was assembled with these Ti/MnCo2O4-Sn3O4 photoanodes, and the PEC approach was used to decolorize the reactive brilliant blue KN-R. The synthesized photoelectrode exhibited a large electroactive region, low charge transfer resistance, high hydroxyl radical generation efficiency, and excellent PEC activity. The optimal composite photoanode presented 86.4 % reactive brilliant blue KN-R removal in 2 h and practical stability in 5 circulation tests. The mechanism during the PEC process was also analyzed and discussed on the basis of radical trapping experiments. In this work, MnCo2O4-Sn3O4 materials possessing Z-scheme heterojunction were constructed, providing insight into the techniques for catalytic purification of organic wastewater.

Investigation of conduction mechanism and UV light response of vertically grown ZnO nanorods on an interdigitated electrode substrate.

Vertically aligned zinc oxide nanorod (ZnO-NR) growth was achieved through a wet chemical route over a comb-shaped working area of an interdigitated Ag-Pd alloy signal electrode. Field-emission scanning electron microscopy images confirmed the formation of homogeneous ZnO-NRs grown uniformly over the working area. X-ray diffraction revealed single-phase formation of ZnO-NRs, further confirmed by energy-dispersive X-ray spectroscopy analysis. Temperature-dependent impedance and modulus formalisms showed semiconductor-type behavior of ZnO-NRs. Two electro-active regions i.e., grain and grain boundary, were investigated which have activation energy ∼0.11 eV and ∼0.17 eV, respectively. The conduction mechanism was investigated in both regions using temperature-dependent AC conductivity analysis. In the low-frequency dispersion region, the dominant conduction is due to small polarons, which is attributed to the grain boundary response. At the same time, the correlated barrier hopping mechanism is a possible conduction mechanism in the high dispersion region attributed to the bulk/grain response. Moreover, substantial photoconductivity under UV light illumination was achieved which can be attributed to the high surface-to-volume ratio of zinc oxide nanorods as they provide high density of trap states which causes an increase in the carrier injection and movement leading to persistent photoconductivity. This photoconductivity was also facilitated by the frequency sweep applied to the sample which suggests the investigated ZnO nanorods based IDE devices can be useful for the application of efficient UV detectors. Experimental values of field lowering coefficient (βexp) matched well with the theoretical value of βS which suggests that the possible operating conduction mechanism in ZnO nanorods is Schottky type. I-V characteristics showed that the significantly high photoconductivity of ZnO-NRs as a result of UV light illumination is owing to the increase in number of free charge carriers as a result of generation of electron-hole pairs by absorption of UV light photons.

A comparative study on the structural, magnetic and dielectric properties of magnesium substituted cobalt ferrites

The structural, morphological, vibrational, dielectric and magnetic properties of polycrystalline samples of Co 1- x Mg x Fe 2 O 4 ( x = 0.00, 0.02, 0.07, 0.12 and 0.30) acquired from sol-gel process has been reported. Structural studies from Rietveld refinement of XRD patterns verified the development of single-phase samples. Raman spectroscopy shows the presence of additional peaks at 620 cm −1 and 660 cm −1 confirming the mixed–spinel structure. With the increase in Mg 2+ substitution, the saturation magnetization decreases from 77.6 emu/g to 56.9 emu/g while the coercive field initially increases ( x < 0.07) and then decreases from 846 Oe to 742 Oe. Except for the x = 0.30 sample, the impedance spectroscopy shows two relaxation peaks in the rest of the samples. The contribution of electroactive regions such as grains, grain boundaries and electrode effect are identified by the comparative study of impedance and modulus spectroscopy. The Nyquist plots are modeled to equivalent circuits accordingly. The activation energy estimated from modulus spectroscopy and Nyquist plots is found to be comparable. The dielectric constants at 323 K are initially found to increase and then decrease. The ac conductivity is interpreted by considering Jonschers’ Power Law as well as Double Power Law and concluded that the small polaron hopping is responsible for electrical conductivity.

Novel Ni3S4/NiS/NC composite with multiple heterojunctions synthesized through space-confined effect for high-performance supercapacitors

The construction of heterojunctions in composite materials to optimize the electronic structures and active sites of energy materials is considered to be the promising strategy for the fabrication of high-performance electrochemical energy devices. In this paper, a one-step, easy processing and cost-effective technique for generating composite materials with heterojunctions was successfully developed. The composite containing Ni3S4, NiS, and N-doped amorphous carbon (abbreviated as Ni3S4/NiS/NC) with multiple heterojunction nanosheets are synthesized via the space-confined effect of molten salt interface of recrystallized NaCl. Several lattice matching forms of Ni3S4 with cubic structure and NiS with hexagonal structure are confirmed by the detailed characterization of heterogeneous interfaces. The C–S bonds are the key factor in realizing the chemical coupling between nickel sulfide and NC and constructing the stable heterojunction. Density functional theory calculations further revealed that the electronic interaction on the heterogeneous interface of Ni3S4/NiS can contribute to high electronic conductivity. The heterogeneous interfaces are identified to be the good electroactive region with excellent electrochemical performance. The synergistic effect of abundant active sites, the enhanced kinetic process and valid interface charge transfer channels of Ni3S4/NiS/NC multiple heterojunction can guarantee high reversible redox activity and high structural stability, resulting in both high specific capacitance and energy/power densities when it is used as the electrode for supercapacitors. This work offers a new avenue for the rational design of the heterojunction materials with improved electrochemical performance through space-confined effect of NaCl.

Flexible freestanding conductive nanopaper based on PPy:PSS nanocellulose composite for supercapacitors with high performance

A freestanding, binder-free flexible polypyrrole: polystyrene sulfonate/cellulose nanopaper (PPy:PSS/CNP) electrode is successfully fabricated by a low-cost, simple, and fast vacuum filtration method for the first time. The hierarchical structure of CNP with high surface area and good mechanical strength not only provides a high electroactive region and shortens the diffusion distance of electrolyte ions, but also mitigates the volumetric expansion/shrinkage of the PPy during the charging/discharging process. The optimized PPy:PSS/CNP exhibits a high areal specific capacitance of 3.8 F cm−2 (corresponding to 475 F cm−3 and 240 F g−1) at 10 mV s−1 and good cycling stability (80.9% capacitance retention after 5000 cycles). The cyclic voltammetry curves of PPy:PSS/CNP at different bending angles indicate prominent flexibility and electrochemical stability of the electrode. Moreover, a symmetric supercapacitor device is assembled and delivers a high areal energy density of 122 µ cm−2 (15 W h cm−3) at a power density of 4.4 mW cm−2 (550 mW cm−3), which is superior to other cellulose-based materials. The combination of high supercapacitive performance, flexibility, easy fabrication, and cheapness of the PPy: PSS/CNP electrodes offers great potential for developing the next generation of green and economical portable and wearable consumer electronics.

In-situ Raman investigation and application of phenazine-based organic electrode in aqueous proton batteries

Aqueous proton batteries (APBs) have aroused attention because of the proton as charge carrier with smaller ionic size and faster kinetics when compared to the metallic ions in aqueous solutions. Although phenazine-based organic compounds with available redox-active sites are considered as promising organic electrode materials, the comprehensive study of their proton-storage behaviors and APB applications is still lacking so far. Herein, a rod-like diquinoxalino-phenazine (DPZ) organic compound is designed and synthetized via a facile dehydration approach. In-situ Raman investigation and theoretical calculation are conducted to probe into the proton redox process of DPZ organic electrode for the first time. It is demonstrated that three CN electroactive regions in each DPZ molecular unit could be simultaneously coordinated with two protons and the redox reaction between CN and CN bonds is highly reversible upon proton insertion/extraction. As expected, the DPZ organic electrode delivers a large proton-storage capacity of ∼ 218 mAh/g and long-term cycle performance without obvious dissolubility in acidic aqueous electrolyte. For real applications, soft-package and wire-shaped APBs based on such DPZ organic electrode are constructed, and they both achieve outstanding electrochemical characteristics, revealing their great potential applications in low-cost, high-safety, and high-performance energy technologies and portable/wearable electronics.

Dielectric relaxation and variable range hopping conduction in sol-gel auto combustion derived La0.7Bi0.3Fe0.5Mn0.5O3 manganite

In the present work, the polycrystalline La0.7Bi0.3Fe0.5Mn0.5O3 maganite was synthesized by sol-gel auto-combustion method. The room temperature X-ray powder diffraction pattern confirmed the orthorhombic phase of the sample with pbnm space group. Frequency and temperature dependent electric modulus and impedance spectroscopic analyses revealed two electro-active components of the material characterized by highly resistive grain boundaries and comparatively conducting grains, respectively. The normalized scaling behavior of modulus plots divulged the temperature independence of the dynamic process in electro-active regions. The fitting of impedance data by the equivalent circuit (RG||QG) + (RGB||QGB) was applied to explore the physical parameters associated with grains and grain boundaries. The dispersion in dielectric permittivity and loss factor at lower frequencies attributed to the space charge polarization were observed. The electrical conductivity obeyed Mott’s T1/4 law and the slope of frequency dependent AC conductivity spectra changed due to multiple activation barriers and active traps, consistent with the variable-range hopping conduction in the material.

High-temperature dielectric behavior of hexagonal HoMnO3

The ac electrical response of hexagonal HoMnO3 was investigated in the temperature range 340≤T≤700K. The combination of impedance and electrical modulus spectra reveal a single dielectric relaxation. However, the ac conductivity in the range 340≤T≤600K revealed two electro-active regions with dissimilar activation energies associated with grain and grain boundary regimes. We suggest that grains have the largest capacitance, whereas grain boundary dominates the overall resistance of the sample. The most interesting was the first-hand observation of a positive temperature coefficient of resistance (PTCR) effect in HoMnO3, and the sample behaves as an extrinsic semiconductor material. Both bulk effects and grain boundary were observed to contribute together to the PTCR phenomena. A correlation between the ac conductivity and dielectric data was built up. Results show that oxygen non-stoichiometry and associated electron holes are liable for the complex dielectric behavior. The scaling behavior of ac conductivity was studied using different formalisms.

Fabrication and characterization of $${\text{Pb}}({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}){\text{O}}_{3}$$ nanofibers for nanogenerator applications

Single-phase lead-zirconate-titanate (PZT) perovskite nanofibers, with $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ composition were synthesized using the electrospinning technique. Poly-vinyl-pyrrolidone (PVP) was used as viscosity controller, size and uniformity of the $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ nanofibers were optimized against different PVP concentrations. The results showed that PVP concentrations play a significant role in the fabrication, homogeneity, uniformity, porosity, and particularly in the diameter of PZT nanofibers. SEM and XRD results revealed the formation of sing-phase $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ nanofibers at 600 °C with an average diameter of ~ 96 nm. The prepared PZT nanofibers exhibited a significantly wide bandgap (~ 3.5 eV) and a high dielectric-constant (~ 1827). The device of single-phase PZT nanofibers was fabricated on interdigitated electrodes to study the current–voltage, impedance spectroscopy, and dielectric characteristics of the PZT nanofibers. The current–voltage characteristics of the fabricated device with PZT nanofibers showed non-ohmic properties. The non-linear I–V characteristics at temperatures between 308 and 408 K indicate two distinct regions. Impedance spectroscopy indicated the presence of non-ideal Debye type behavior in $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ nanofibers and was ascribed to the existence of heterogeneity in the sample. The measured capacitances were assigned to two electro-active regions in the prepared $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ nanofibers. A proto-type piezoelectric nanogenerator based on PZT nanofibers was fabricated to study the piezoelectric properties of $${\text{Pb}}\left({\text{Zr}}_{0.5}{\text{Ti}}_{0.5}\right){\text{O}}_{3}$$ nanofibers. PZT nanofibers were aligned on interdigitated electrodes of silver wire, which demonstrated piezoelectric performance and delivered an output voltage of ~ 40 V under periodic stress applications.

Polymer based nickel ferrite as dielectric composite for energy storage applications

Graphene oxide (GO) and polymer based nanocomposites are emerging as a new class of materials having potential for flexible electronic devices and modern day energy storage devices. The traits like high mechanical strength, non-corrosive nature, low weight, being cost-effective, flexible, thermal and electrically insulated have made polymer based nano architectures highly effective for utilizing in energy storage applications. In the present research, the variation in structure, morphology and dielectric response of polypyrrole (PPy) is investigated by adding the nickel ferrite (NiFe2O4) and GO in it. The nano-materials, PPy, NiFe2O4 and GO were prepared by pyrrole’s polymerization, sol‒gel auto-combustion method and modified Hummer’s method, respectively. The solution mixing method was carried out to form GO/NiFe2O4/PPy nanocomposites with different concentrations by slowly mixing the already equipped nanomaterials. X-ray diffraction technique was employed for phase identification of as-prepared nanocomposites. The surface study and elemental composition was examined via field emission scanning electron microscope and energy dispersive X-ray spectroscope, respectively. The dielectric response of these samples was probed using impedance analyzer that was found to be in good agreement with Maxwell-Wagner model and Koop’s Phenomenological theory. Effective contribution of different electro-active regions was investigated from Nyquist plots.

Ferroelectric polymer/ceramic nanocomposites with low energy losses

AbstractIn order to meet the continuously increasing demand of modern electronic industries, there is an urgent need to develop the advanced energy storage materials. In this regard, polymer‐based dielectric composites are promising materials for futuristic technological applications. Herein, we synthesized a (1 − x) PVDF + xBFO composite by means of sol‐gel auto‐combustion route to explore its energy storage capabilities using impedance spectroscopy. After synthesis, field emission scanning electron microscope was utilized to examine exterior texture and obtained images showed the uniform distribution of BiFeO3 particles in polyvinylidene fluoride matrix with considerable amount of porosity. The particle size was measured using the ImageJ software. In conjunction with scanning electron microscopy, the stoichiometric amounts of all constituents were confirmed using energy dispersive X‐rays spectroscopy, working on the measurement of relative abundance of X‐rays vs their energy. Dielectric traits of these polymer composite ceramics were explored using precision impedance analyzer with varying frequency from 20 Hz to 20 MHz which explored their energy storage potential. The analysis of Nyquist plot helped to define the range of impedance spectrum where the different electroactive regions participated significantly in impedance response of the material. The effect of reinforcement contents on the nature of hopping length and relaxation phenomenon was probed through the complex modulus analysis. The energy storage capacity in terms of energy density was analyzed by checking the polarization response of the composite material in varying electric field which is a key feature for grading a material for energy storage devices.

Electrochemical impedance spectroscopic analysis of aluminum and gallium mixed matrix membranes

Mixed matrix membrane revolutionized the field of electrochemistry with its multiple applications as a solid electrolyte, actuator, sensor, and storage device, because of its better processability, flexibility, and light-weight. The present study is designed to investigate the role of hybrid filler in the electrochemical properties of the mixed matrix membrane. For this purpose, aluminum and gallium hybrids with indole and its derivatives were synthesized using the post-modification method. Then, synthesized hybrids were dispersed evenly into the polysulfone matrix and developed its membrane using the immersion precipitation phase inversion method. The FTIR result of aluminum and gallium hybrids identified the absorption bands of −C=C (1485–1400 cm−1), −CN (1340–1122 cm−1), and –NH (1625–1535 cm−1) with repeating units of Al–O (1178 cm−1) and Ga-O (1132–1117 cm−1). SEM images showed the spherical-shaped aluminum oxide and rod-shaped gallium oxide. XRD pattern corresponded to the cubic and trigonal crystal system of aluminum and gallium oxides. Electrochemical impedance study showed significant improvement in the electrical behavior of aluminum and gallium mixed matrix membranes where aluminum and gallium hybrids as a filler create the continuous network for the easy transportation of the charge carriers. The existence of the peaks at a similar position in both impedance and modulus formalisms suggests relaxations of the same type of charge species at the same type of electroactive region and disclose the real picture of the material.

Structure, Dielectric Properties and Impedance Spectroscopy of BaTi0.97(Zn,V,Ta)0.03O3 Ceramics

BaTi0.97Zn0.01V0.01Ta0.01O3and#172; sample was prepared using the conventional mixed oxide sintering route. The samples were characterized using X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy and Impedance spectroscopy. Structure of the sample was analyzed using Rietveld analysis which showed the formation of tetragonal symmetry. Raman spectroscopy was also in agreement with the XRD results, further indicating the ferroelectric signature in the sample. Electrical microstructure analyzed by impedance spectroscopy analysis revealed two electroactive regions in the sample, belonging to the grain boundary and bulk. An extrinsic conduction mechanism was observed across the sample. Dielectric properties as a function of temperature demonstrated phase transition (TC) at ~ 94 and#176;C, with relative permittivity ~ 3280 at TC. Antiferroelectric-like double hysteresis loops were observed in P-E analysis. The energy storage density was calculated to be 0.26 J/cm3 at an electric field of 50 kV/cm, indicating that BaTi0.97Zn0.01V0.01Ta0.01O3and#172; ceramics can be potentially useful base materials for high density energy storage capacitors.