Observation of ionic conductivity on PUA-TBAI-I2 gel polymer electrolyte

Jatropha oil-based polyurethane acylate gel polymer electrolyte was mixed with different concentrations of tetrabutylammonium iodide salt (TBAI). The temperature dependences of ionic conductivity, dielectric modulus and relaxation time were studied in the range of 298 to 393 K. The highest ionic conductivity of (1.88 ± 0.020) × 10–4 Scm−1 at 298 K was achieved when the gel contained 30 wt% of TBAI and 2.06 wt% of I2. Furthermore, the study found that conductivity-temperature dependence followed the Vogel-Tammann Fulcher equation. From that, it could be clearly observed that 30 wt% TBAI indicated the lowest activation energy of 6.947 kJ mol−1. By using the fitting method on the Nyquist plot, the number density, mobility and diffusion coefficient of the charge carrier were determined. The charge properties were analysed using the dielectric permittivity, modulus and dissipation factor. Apart from this, the stoke drag and capacitance were determined.

Superlative Photoelectrochemical Properties of 3D MgCr- LDH Nanoflowers influencing towards Photoinduced Water Splitting Reactions

Layered double hydroxides (LDHs) are competent photocatalysts for water splitting reactions, vital to produce solar fuels, but their restricted available reactive sites, slow mass and charge transfer, are yet remain a challenge. To surmount these lacunas, Nanoflowers-like three-dimensional (3D) open structure of MgCr-LDH have been designed in a substrate-free path by one-step formamide assisted hydrothermal treatment followed by visible light irradiation and utilized as efficient photocatalysts for the H2 and O2 production. The structural, morphological, optical and photoelectrochemical (PEC) properties of the MgCr-LDH nanoflowers were extensively examined, by various physico-chemical characterization techniques. Moreover, the well-designed 3D MgCr-LDH nanoflowers with open structure were formed by a stacking of numerous 2D nanosheets, which inherently triggered with magnificent PEC properties, including high current density of 6.9 mA/cm2, smallest arc of the Nyquist plot (59.1 Ω cm−2) with photostability of 6000 s thereby enhancing the photocatalytic water splitting activity along. Moreover such a perfectly self-stacked 2D nanosheet in 3D MgCr-LDH possess defect sites as enriched 50% oxygen vacancy resulting a good contact surface within the structure for effective light absorption and easy electron and hole separation, facilitates the adsorption of protons and intermediate of water oxidation. Further, the doped Cr3+ pull up electrons from water oxidation intermediates, thereby displaying superior photocatalytic H2 and O2 production activity of 1315 µmol/h and 579 µmol/h, respectively. Favorable oxygen vacancy type defect surface with Cr3+ dopant in MgCr-LDH triggers significant PEC properties, which influences the easy charge transfer and separation mechanism and robustly enhance the photocatalytic performance of the nanoflower.

Electrochemical properties of La9.33Si6O26(LSO)-La0.8Sr0.2Ga0.8Mg0.2O2.55(LSGM) electrolyte over NiO and La0.1Ca0.9MnO3(LCM) electrodes

The electrochemical properties of La9.33Si6O26(LSO)-La0.8Sr0.2Ga0.8Mg0.2O2.55(LSGM) electrolyte composites have been evaluated over NiO and La0.1Ca0.9MnO3 (LCM) electrodes using symmetric and asymmetrical cells of NiO/LSO-LSGM/NiO and NiO/LSO-LSGM/LCM, respectively. The Nyquist plot obtained from this study suggested that the new electrolyte system exhibits excellent performance over the NiO and LCM electrodes and shows an ideal Randel cell electrical circuit characteristic in both NiO/LSO-LSGM/NiO and NiO/LSO-LSGM/LCM cells. The area-specific resistance (ASR) and, the activation energy (Ea) of NiO/LSO-LSGM/NiO from the Arrhenius plot are lower than the NiO/LSO-LSGM/LCM, which is 0.30 Ω cm-2 and of 0.74 eV versus 0.40 Ω cm-2 with Ea of 0.76 eV, respectively.

Analytical Impedance of Oxygen Transport in the Channel and Gas Diffusion Layer of a PEM Fuel Cell

An analytical model for impedance of oxygen transport in the gas--diffusion layer (GDL) and cathode channel of a PEM fuel cell was developed. The model is based on transient oxygen mass conservation equations coupled to the proton current conservation equation in the catalyst layer. An analytical formula for the ``GDL+channel'' impedance was derived assuming that the oxygen and proton transport in the cathode catalyst layer (CCL) are fast. In the Nyquist plot, the resulting impedance consisted of two arcs describing oxygen transport in the air channel (low--frequency arc) and in the GDL. The characteristic frequency of GDL arc depends on the CCL thickness: large CCL thickness strongly lowers this frequency. At small CCL thickness, the high--frequency feature on the arc shape forms. This effect is important for identification of peaks in distribution of relaxation times spectra of low--Pt PEMFCs.

Corrosion Inhibition of Sodium Silicate with Nanosilica as Coating in Pre-Corroded Steel

This study was conducted to investigate the potential of using sodium silicate with nanosilica as a treatment to inhibit the progress of corrosion in steel specimens that are already corroded. Steel specimens measuring 16 mm in diameter and 4 mm in thickness were prepared and subjected to pre-corrosion by immersion to 3.5% NaCl solution. Two sets of specimens were then dip-coated with sodium silicate containing nanosilica. One set was coated with 1% nanosilica, and the other was coated with 2.5% nanosilica. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20 Hz to 20 MHz frequency range. Compared with the sodium silicate coating with 1% nanosilica, the sodium silicate coating with 2.5% nanosilica had a larger semi-circle curve in the Nyquist plot. Similarly, the sodium silicate coating with 2.5% nanosilica also showed larger magnitudes of impedance at the low-frequency region and larger phase angles at the high-frequency regions in the Bode plot. These results imply that the sodium silicate coating with 2.5% nanosilica coating demonstrated better capacitive behavior. In addition, equivalent circuit modelling results also showed that the sodium silicate coating with 2.5% nanosilica had higher coating resistance and lower coating capacitance as compared to the sodium silicate coating with 1% nanosilica. Doi: 10.28991/cej-2021-03091761 Full Text: PDF

Synthesis and Characterization of Non-Stoichiometric Li1.1Co0.3Fe2.1O4 Ferrite Nanoparticles For Humidity Applications

Humidity sensor plays a crucial role in determining the efficiency of materials and the precision of apparatuses. To measure and control humidity, a non-stoichiometric Li1.1Co0.3Fe2.1O4 mesopores sensor is synthesized by a modified citrate auto combustion technique. The XRD study confirms that prepared nanoparticles are cubic spinel structures having Fd3m space group. The crystallite size is approximate 36 nm. Thermal analyses measurements confirm that the samples become thermally stable starting from 600 °C. Additionally, the kinetic studies of the prepared samples are calculated via a pseudo-first-order kinetic model. The temperature dependence of AC conductivity is found to increase with increasing the temperature. These observations are explained in various models. The resistivity mechanism of humidity sensors is studied via Complex impedance spectroscopy (CIS). Its impedance data is fitting to a corresponding circuit, to achieve a simulation of the sample under study. This fitting is detected by the Nyquist plot (Cole-Cole). The obtained data confirms that the studied samples are very sensitive to humidity and can be commercially used as a humidity sensing element.

Technology agnostic frequency characterization methodology for memristors

Over the past decade, memristors have been extensively studied for a number of applications, almost exclusively with DC characterization techniques. Studies of memristors in AC circuits are sparse, with only a few examples found in the literature, and characterization methods with an AC input are also sparingly used. However, publications concerning the usage of memristors in this working regime are currently on the rise. Here we propose a "technology agnostic" methodology for memristor testing in certain frequency bands. A measurement process is initially proposed, with specific instructions on sample preparation, followed by an equipment calibration and measurement protocol. This article is structured in a way which aims to facilitate the usage of any available measurement equipment and it can be applied on any type of memristive technology. The second half of this work is centered around the representation of data received from following this process. Bode plot and Nyquist plot representations are considered and the information received from them is evaluated. Finally, examples of expected behaviors are given, characterizing simulated scenarios which represent different internal device models and different switching behaviors, such as capacitive or inductive switching. This study aims at providing a cohesive way for memristor characterization, to be used as a good starting point for frequency applications, and for understanding physical processes inside the devices, by streamlining the measuring process and providing a frame in which data representation and comparison will be facilitated.

Coating activated carbon from coconut shells with Co3O4/CeO2 for high-performance supercapacitor applications: An experimental study

Activated carbon from coconut shells is a low-cost, environmentally friendly material that is available for fabricating the electrodes for electric double-layer capacitance supercapacitors. As such, activated carbon derived from coconut shells was coated with Co3O4/CeO2, and its electrical and ionic conductivity were evaluated. The ternary technique for selecting materials was systematically investigated with an economical process. The Co3O4/CeO2 coating that was formed on the activated carbon coconut shells was deemed AC-Co3O4-CeO2. The 90-05-05 composite was the best electrode for electric double-layer capacitance supercapacitors, resulting in high conductivity (0.62 x 103 S·cm2), low series resistance and internal resistance (based on the Nyquist plot), and the charge-discharge was able to reach 0.56 V for 90 seconds (1A/g). Therefore, activated carbon coconut shells coated in Co3O4/CeO2 can promote the necessary characteristics of electrodes needed for electric double-layer capacitance supercapacitors.

Effects of lead exposure on blood electrical impedance spectroscopy of mice

Background Lead is a nonessential heavy metal, which can inhibit heme synthesis and has significant cytotoxic effects. Nevertheless, its effect on the electrical properties of red blood cells (RBCs) remains unclear. Consequently, this study aimed to investigate the electrical properties and the electrophysiological mechanism of lead exposure in mouse blood using Electrical Impedance Spectroscopy (EIS) in 0.01–100 MHz frequency range. Data characteristic of the impedance spectrum, Bodes plot, Nyquist plot and Nichols plot, and Constant Phase Element (CPE) equivalent circuit model were used to explicitly analyze the differences in amplitude–frequency, phase–frequency, and the frequency characteristics of blood in electrical impedance properties. Results Compared with the healthy blood in control mice, the changes in blood exposed to lead were as follows: (i) the hematocrit decreased; (ii) the amplitude–frequency and phase–frequency characteristics of electrical impedance decreased; (iii) the characteristic frequencies (f0) were significantly increased; (iv) the electrical impedance of plasma, erythrocyte membrane, and hemoglobin decreased, while the conductivity increased. (v) The pseudo-capacitance of cell membrane (CPE_Tm) and the intracellular pseudo-capacitance (CPE-Ti) were decreased. Conclusions Therefore, EIS can be used as an effective method to monitor blood and RBC abnormalities caused by lead exposure. The electrical properties of the cells can be applied as an important observation in the evaluation of the toxic effects of heavy metals.