Electrochemical Impedance Characteristics Research Articles

Impedance Characteristics of Berea Sandstone Cores in the Process of CO<sub>2</sub> Injection Displacement with Saturated Brine

As an important means of CO<sub>2</sub> geological storage leakage monitoring, resistivity monitoring technology is of great significance to the safety and stability of CCUS project. In order to study the electrical signal response rule of the evolution of CO<sub>2</sub> saturation in the reservoir, a joint core displacement experiment system of electrochemical impedance analysis and microfocus X-ray CT was designed and constructed to simulate the process of CO<sub>2</sub> displacement of brine in Berea sandstone cores under stratigraphic temperature and pressure conditions. The electrochemical impedance characteristics of the core-fluid system are analyzed by electrochemical impedance spectroscopy. The experimental results show that at lower temperature and pressure, it is more difficult for CO<sub>2</sub> to invade the pore space occupied by the brine in situ, resulting in drastic changes in CO<sub>2</sub> plane saturation along the displacement direction. With the increase of temperature and pressure, the CO<sub>2</sub> saturation curve becomes smoother and the migration and displacement front becomes even. The Cole equivalent circuit model is used to describe the conduction mode of AC electrical signals inside the core, and the electrochemical impedance characteristic analysis focusing on the high frequency region shows that the system impedance increases with the increase of CO<sub>2</sub> saturation, and decreases with the increase of scanning frequency. In addition, the changes of impedance characteristics in the electrochemical impedance spectroscopy not only reflect the pore structure characteristics of the core, but also reveal the evolution law of CO<sub>2</sub> saturation in the porous medium. With the increase of CO<sub>2</sub> saturation, the low pore space is gradually occupied by CO<sub>2</sub>, and the residual brine connectivity of the pore space as a conductive component decreases. The decrease of the internal conductive circuit leads to the rapid increase of the impedance, which is consistent with the change of resistance and capacitance when fitting the Cole equivalent circuit model.

Synergistic effect of morphology and Co+2/Co+3 ratio on supercapacitor performance of Co3O4/vertical graphene nanosheets binder-free hybrid electrodes

Cobalt oxide (Co3O4) nanostructures decorated vertical graphene nanosheets (VGN) based hybrid electrodes are synthesized to fabricate binder-free high-performance supercapacitors. Tuning of microstructure, morphology, and stoichiometry of Co3O4 nanostructures is endeavoured by growing them in an oxygen medium using the pulsed laser deposition (PLD) technique. The variation in background oxygen pressure transformed the growth morphology of Co3O4 nanostructures from smooth film to nano-particulate caterpillar, flower, and cloud-like. Additionally, the variation in background oxygen pressure significantly influences the Co+2/Co+3 ratio. Moreover, the morphology variation led to a significant change in electrochemical active surface area (ECSA), and the electrochemical impedance characteristics varied from highly capacitive to nearly diffusive nature. These Co3O4/VGN hybrid electrodes exhibited an areal capacitance value of 32 mF/cm2 (1900 F/g) @ 20 mV/s with cyclic stability of 87 % after 3000 charge-discharge (CD) cycles in 1 M KOH electrolyte. Herein, a correlation between morphology, ECSA, and Co+2/Co+3 ratio with areal capacitance values is established. Finally, an asymmetric coin-cell device is fabricated using the Co3O4/VGN as a positive electrode and oxygenated VGN as a negative electrode, respectively. The coin-cell device exhibited a 4 mF/cm2 capacitance with energy and power densities of about 1.8 μWh/cm2 and 218.8 μW/cm2, respectively. Additionally, the coin-cell device displayed excellent cyclic stability of 92% after 5000 CD cycles. The potential utilization of this device is demonstrated by lighting an LED.

Electrochemical impedance characteristics and degradation behaviors of carbon fiber reinforced composite attacked by HF solution

PurposeThe purpose of this study is to ensure the safe use of carbon fiber composite pressure vessels in the nuclear industry environment.Design/methodology/approachThis study investigated the degradation behaviors of carbon fiber reinforced composite (CFRP) using the specific corrosive media HF solution, with a focus on the damage to the surface epoxy layer. The degradation behaviors of CFRP in HF solution were examined by electrochemical methods and surface characterization, using HCl, NaCl and NaF solution for comparison.FindingsThe results showed that the specimen in HF solution will have a value of |Z|0.01 Hz one order of magnitude lower, a substantially lower contact angle, more breakage of the surface epoxy and the stronger O─H peak and weaker C─O─C peak in the Fourier transform infrared spectrum, indicating severe hydrolytic damage to the surface epoxy.Originality/valueThe work focuses on the degradation damage to CFRP surface epoxy by specific corrosive media HF.

Impedance Investigation of Silicon/Graphite Anode during Cycling

Silicon/graphite material is one of the most promising anodes for high-performance lithium-ion batteries. However, the considerable deformation occurring during the charge/discharge process leading to its degradation hinders its application. Research on the electrochemical performance of silicon/graphite anode have mainly focused on its cyclic performance and microscopic mechanism, whilst the correlation between electrochemical performance and the mechanical deformation of batteries at the cell level is in few numbers. In this study, the electrochemical performance and cycling performance of the cells in Ah-level silicon/graphite anode pouch cells with different SiO weight ratios (5 wt.%, 10 wt.%, and 20 wt.%) in the anode, and LiNi0.8Co0.1Mn0.1 as the cathode are investigated by quantitative analysis. It is found that cells with different SiO weight ratios in anodes under a different state of charge (SOC) and state of health (SOH) demonstrate remarkable differences in electrochemical impedance characteristics. The results show that SOC, SOH and the weight ratios of SiO are the main factors affecting the impedance characteristics for batteries with silicon/graphite anode, which is deeply related to the change in the thickness of the electrode during lithiation/delithiation. This research facilitates the application of EIS in battery management and the design of silicon/graphite anode lithium-ion batteries.

Revealing the electrochemical impedance characteristics of lithium-ion battery (nickel-cobalt-aluminum vs. graphite) under various alternating current amplitudes

To reveal the impact of alternating current (AC) amplitude on impedance, this study investigates the electrochemical impedance with different AC amplitudes for a lithium-ion battery (NCA vs. graphite) and half cells under different states of charge (SOCs), at room and low temperatures. To determine the relationship of different polarization processes between the full cell and half cells, the symmetric cells and the distribution of relaxation times (DRT) are utilized for electrochemical impedance spectroscopy (EIS) analysis. The experimental results indicate that the medium- and low-frequency impedance arcs gradually shrink with the increase of the AC amplitude at low temperatures. DRT focuses on the anode solid electrolyte interphase (SEI), cathode electrolyte interphase (CEI), and charge transfer processes. It is proved that the impedance arc shrinkage is determined by the nonlinear relationship that can be described by the Butler-Volmer equation between current and resistances of the SEI and the charge transfer processes. When the AC amplitude increases to a certain extent, lithium plating also causes impedance arc shrinkage. Moreover, the impedance arc shrinkage of the full cell is mainly affected by the NCA cathode under low SOC. At medium and high SOCs, it is determined jointly by the NCA cathode and graphite anode.

Experimental Study of the Electrochemical Impedance Characteristics and Mechanical Properties of High Belite Sulfoaluminate Cement

Experimental Study of the Electrochemical Impedance Characteristics and Mechanical Properties of High Belite Sulfoaluminate Cement

Electrochemical response and effect evaluation of high belite sulphoaluminate cement combined with red mud-fly ash on solidification of Cu2+-contaminated kaolin

In this paper, the solidification of Cu2+-contaminated kaolin by high belite sulphoaluminate cement (HBSC) combined with red mud (RM) and fly ash (FA) was investigated. The effects of solidification/stabilization (S/S) and its electrochemical responses were experimentally explored by mixing RM and FA as the main raw materials with small amounts of low-energy HBSC and quicklime serving as solidifiers of heavy metal contaminated soil. The solidification mechanism of the solidifier on Cu2+ and its solidification effect were then systematically investigated by analyzing the unconfined compressive strength (UCS) of the solidified body, toxic leaching, permeation characteristics, and surfaces morphologies. The study of the electrochemical response of the solidified body during the solidifying and remediation process allowed the development of an evaluation method for repairing the effect of Cu2+-contaminated kaolin based on electrochemical impedance spectroscopy (EIS). The results showed that the strength, impermeability, and leaching toxicity of solid waste co-HBSC solidifying of contaminated soil met industrial requirements. The incorporation of low energy consumption HBSC generated a mass ratio of RM to FA of 8:2 with the best solidification effect. Heavy metals can be absorbed by chemical precipitation, displacement reactions, and encapsulation by hydration gels. In addition, the electrochemical impedance characteristics of the solidified bodies were found consistent with the conventional evaluation of the solidification effect. In sum, HBSC synergistic solid waste solidifier looks very promising for use in the S/S remediation of Cu2+-contaminated soil.

Electrochemical Impedance Characteristics of a Low-Temperature Single Cell for CO2/H2O Co-Reduction to Produce Syngas (CO+H2)

In this study, the electrochemical impedance characteristics of CO2/H2O co-reduction to produce CO/H2 syngas were investigated in a low-temperature single cell. The effect of the operating conditions on the single-cell performance was evaluated at different feed concentrations and cell voltages, and the corresponding electrochemical impedance spectroscopy (EIS) data were collected and analyzed. The Nyquist plots exhibited two semicircles with separated characteristic frequencies of approximately 1 kHz and tens of Hz. The high-frequency semicircles, which depend only on the catholyte concentration, could be correlated to the charge transfer processes in competitive CO2 reduction and hydrogen evolution reactions at the cathodes. The EIS characteristics of the CO2/H2O co-reduction single cell could be explained by the equivalent circuit suggested in this study. In this circuit, the cathodic mass transfer and anodic charge transfer processes are collectively represented by a parallel combination of resistance and a constant phase element to show low-frequency semicircles. Through nonlinear fitting using the equivalent circuit, the parameters for each electrochemical element, such as polarization resistances for high- and low-frequency processes, could be quantified as functions of feed concentration and cell voltage.

THE PREPARATION AND CHARACTERIZATION OF A CERIUM-BASED RARE EARTH CONVERSION COATING ON MAGNESIUM ALLOY AZ91D AND ITS DEGRADATION IN 3.5% NaCl SOLUTION

For rare earth conversion coatings (RECCs) on the surface of magnesium alloy (MA), their electrochemical impedance spectroscopy (EIS) evolution and characteristics during the process of coating degradation in environmental media were involved relatively few. In this work, a cerium-based RECC (Ce-RECC) was prepared on the surface of MA AZ91D with chemical conversion technique; for Ce-RECC, its morphology was characterized with optical microscope (OM) and scanning electron microscope (SEM) observations, its composition was characterized with energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) detections, and its protection was characterized with potentiodynamic polarization and EIS tests. Ce-RECC exhibited a mud-crack morphology and was composed of Ce and O mainly, and the corrosion current density ([Formula: see text]) and the coating resistance ([Formula: see text]) for Ce-RECC-coated MA AZ91D were smaller and larger than those for bare MA AZ91D, respectively. During the process of Ce-RECC degradation in 3.5% NaCl solution, the EIS of Ce-RECC-coated MA AZ91D always comprised a capacitive loop at high frequency region and an inductive loop at low frequency region, which was independent of time extension; however, the value of [Formula: see text] for Ce-RECC decreased gradually with the extension of time, and the total degradation of Ce-RECC consumed 77[Formula: see text]h.

Electrochemical impedance characteristics at various conditions for commercial solid–liquid electrolyte lithium-ion batteries: Part. 2. Modeling and prediction

Solid–liquid electrolyte lithium-ion batteries (SLELBs) have good commercial viability in electric vehicle applications because they combine the safety of solid electrolyte lithium-ion batteries with the high ionic conductivity of liquid electrolyte lithium-ion batteries (LELBs). The safe and efficient operation of electric vehicles is inseparable from the key battery management algorithms such as battery state of charge (SOC), state of health and state of power estimation. In the process of designing battery management algorithms for SLELBs, it is essential to have an accurate understanding of battery behavior under different influencing factors and to build a high-fidelity battery simulation model. Electrochemical impedance spectroscopy (EIS) can be used to study the electrode process dynamics and ion transport mechanism in lithium-ion batteries. It is an urgent challenge to use EIS to experiment and analyze the characteristic impedances of SLELBs under the full-scale factors and to construct the battery model and simulate the battery impedance under the premise of a reasonable number of tests.In this series of two papers, we first propose a regression model of temperature and SOC One-Way factor SLELB characteristic impedances through a full-scale experimental design under the theoretical framework of experimental optimization design and statistical analysis. Then, in order to construct the model under the premise of a reasonable number of tests, an orthogonal experiment is designed and an orthogonal piecewise polynomial Arrhenius-simplified equivalent circuit model (SECM) for SLELB impedance prediction of the Two-Way factor of temperature and SOC is established. These models can accurately describe SLELB behavior under different factors, improve the understanding of SLELB electrode processes, and predict the impedance spectrum of SLELB, all of which support the key battery management algorithms. In the first paper, the characteristic impedances in the EIS were identified to facilitate a systematic analysis at different temperatures and SOCs in a full-scale experimental design. The Arrhenius and polynomial regression models of the One-Way factor SLELB characteristic impedances of temperature and SOC were established.In this second paper, an equivalent circuit model (ECM) based on the first principles of the electrode process of SLELB is established and simplified according to the EIS impedance frequency range to obtain the SECM. In order to construct the battery model under the premise of a reasonable number of experiments, we design an orthogonal experiments scheme to reduce the number of experiments to half that of the full-scale experiments. An orthogonal piecewise polynomial Arrhenius (OPPA) temperature and SOC Two-Way factor parameter model is established using ANOVA considering the interaction of the ECM model parameters. The experimental results show that OPPA has an accurate prediction performance for ECM parameters with a reasonable number of segments and orders. The predictive performance of OPPA-SECM is similar to that of full-scale piecewise polynomial Arrhenius (FPPA)-SECM, and the number of OPPA-SECM experiments is reduced by half that of FPPA-SECM experiments.

Revealing the Electrochemical Impedance Characteristics of Lithium-Ion Battery (Nickel-Cobalt-Aluminum vs. Graphite) Under Various Alternating Current Amplitudes

Revealing the Electrochemical Impedance Characteristics of Lithium-Ion Battery (Nickel-Cobalt-Aluminum vs. Graphite) Under Various Alternating Current Amplitudes

Electrochemical impedance characteristics at various conditions for commercial solid–liquid electrolyte lithium-ion batteries: Part 1. experiment investigation and regression analysis

Solid–liquid electrolyte lithium-ion batteries (SLELBs) have good commercial viability in electric vehicle applications because they combine the safety of solid electrolyte lithium-ion batteries with the high ionic conductivity of liquid electrolyte lithium-ion batteries (LELBs). The safe and efficient operation of electric vehicles is inseparable from the key battery management algorithms such as battery state of charge (SOC), state of health and state of power estimation. In the process of designing the battery management algorithms for SLELBs, it is essential to have an accurate understanding of battery behavior under different influencing factors and build a high-fidelity battery model. Electrochemical impedance spectroscopy (EIS) can be used to study the electrode process dynamics and ion transport mechanism in lithium-ion batteries. However, it can be a huge challenge to use EIS to experiment and analyze the characteristic impedances of SLELBs under the full-scale factors, and to construct the battery model and simulate the battery impedance under the premise of a reasonable number of tests.Over a series of two papers, we first propose a regression model of temperature and SOC One-Way factor SLELB characteristic impedances through full-scale experimental design under the theoretical framework of experimental optimization design and statistical analysis. Then, in order to construct the model under the premise of a reasonable number of tests, the orthogonal experiment is designed, and the orthogonal piecewise polynomial Arrhenius - simplified equivalent circuit model for SLELB impedance prediction of the Two-Way factor of temperature and SOC is established. These models can accurately describe SLELB behavior under different factors, improve the understanding of the SLELB electrode process, and predict the impedance spectrum of SLELB, support the key battery management algorithms.In this first paper, EIS is used to analyze the electrode process kinetics of Li7La3Zr2O12 SLELBs at different temperatures and SOCs in a full-scale experimental design. Furthermore, the characteristic impedances in the EIS are identified to facilitate a systematic analysis of the battery performance. The Arrhenius model and polynomial model are used to perform the regression analysis of temperature and SOC One-Way factor SLELB characteristic impedances. Experimental results show that these models can achieve a high precision regression for One-Way factor characteristic impedances.

Asymmetric behavior of solid oxide cells between fuel cell and electrolyzer operations

The electrochemical performance of solid oxide cells (SOCs) is investigated under both fuel cell and electrolyzer operations to understand their asymmetric behavior between the two operation modes. The current–voltage and electrochemical impedance characteristics of a hydrogen-electrode-supported cell are experimentally analyzed. Also, a numerical model is developed to reproduce the cell performance and to understand the internal resistances of the cell. Partial pressures of supplied gas and load current are varied to evaluate their effects on the cell performance. The gas partial pressures of hydrogen and steam supplied to the hydrogen electrode are kept equivalent so that the cell performance can be fairly compared between the two operation modes when the same current is applied. It is found that the origin of the asymmetry is mostly from the hydrogen electrode; both activation and concentration overpotentials show asymmetric behavior particularly at high current densities. A numerical experiment is also conducted by deliberately changing parameters in the model. Asymmetry in the activation overpotential is found to be originated from the non-identical charge-transfer coefficients in the Butler–Volmer equation and also from the non-uniform gas concentration formed in the hydrogen electrode under current-biased conditions. On the other hand, asymmetry in the concentration overpotential is associated with the non-equimolar counter diffusion of hydrogen and steam caused by the effect of Knudsen diffusion. Therefore, enhancing gas transport in the hydrogen electrode and reducing the contribution of Knudsen diffusion are effective approaches to reduce asymmetry not only in the concentration overpotential but also in the activation overpotential.

Effect of Electrolyte Composition on the Performance of Coal Char-Derived Carbon Supercapacitors

Research regarding supercapacitors has vastly grown over the past decade. The advantages of supercapacitors include high power density, rapid charge/discharge capability, and a long cycle life. Current applications of supercapacitors are limited by the need to develop new, low-cost electrode materials for electric double layer capacitors and pseudocapacitors [1]. Coal char is the solid product of a low-temperature coal carbonization process, and is currently used primarily as an ultra-low-cost fuel for electric power generation. As such, coal char consists mainly of hard carbons and ash [2]. Upon ash removal, the hard carbons in coal char may serve as a promising, low-cost, supercapacitor electrode material. This research will present the use of inexpensive coal char as an electrode material for supercapacitors, with particular focus on the effects of various electrolyte compositions on the performance of coal-derived carbon supercapacitors.Electrolyte composition plays a large role in the electrochemical properties of a supercapacitor, affecting: ion interactions with electrode surface functional groups; electric double layer capacitance; thermal stability; and allowable voltage range. In this work, bituminous grade coal char from a Utah mine is pulverized, pyrolyzed, and washed in a base solution followed by an acid solution to remove residual ash. SEM imaging and BET surface area measurements are used to characterize the coal. The purified coal char is mixed into a slurry of coal char, Super P binder, and dimethylformamide, then applied on a stainless-steel plate to create supercapacitor electrodes. Three-electrode open-cell electrochemical measurements are used to characterize the supercapacitor performance of the coal char in varying electrolyte solutions using a Gamry Interface 1000E potentiostat. The different electrolytes explored include: aqueous acid 0.5 M H2SO4, aqueous base 6 M KOH, and aqueous neutral solutions 0.5 M Na2SO4, 4 M LiNO3, water-in-salt electrolyte using 12.5 M NaClO4, . Voltage range, specific capacitance, electrochemical impedance, and charge-discharge characteristics of the coal char in the different electrolytes are characterized by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy measurements. The results provide important insight into the optimal electrolyte composition for use with coal char supercapacitor electrodes, and contribute to current understanding of electrode-electrolyte interactions in carbon supercapacitors.This work is supported in-part by NSF Award #1742696.Reference1.Rakesh Kumar Gupta, Mukul Dubey, Parashu Kharel, Zhengrong Gu, Qi Hua Fan, Biochar activated by oxygen plasma for supercapacitors, Journal of Power Sources, Volume 274, 2015, Pages 1300-1305.2. H. H. Schobert, Coal; The Energy Source of the Past and Future, pg. 9, American Chemical Society, Washington (1987). Figure 1

Fabrication of TiO2/CdS heterostructure photoanodes and optimization of light scattering to improve the photovoltaic performance of dye-sensitized solar cells (DSSCs)

Currently, the TiO2/CdS photoanodes based dye-sensitized solar cells (DSSCs) have shown extraordinary developments in the photo-conversion efficiency. In this report, pristine TiO2, CdS and various molar ratios of TiO2/CdS photoanodes were prepared by one step microwave irradiation route and followed by doctor blade method. The sheet-like morphology of the TiO2 and CdS nanoparticles were clearly evident from the SEM and TEM images. A significant reduction bandgap with enhanced light absorption and rapid prevention of electron hole pair was explored by UV-DRS and PL studies. The photocurrent density–voltage (J–V) and electrochemical impedance (EIS) characteristics were analyzed for assembled solar cell. The photo-conversion efficiency of 12.8% was obtained with the configuration TiO2/CdS (200 mg) that represent a 2.5-fold increment compared to bare TiO2 (5.33%) as well as commercial Pt (6.11%). The experimental results are discussed.

Geometrical effects on ionic diffusion in carbon‐carbon symmetric supercapacitors

There is a great need to understand the structural dependence of supercapacitors for the development of advanced electrode materials that can be used to improve the electrochemical performance and structural integrity. In this work, we investigate the effects of the size and pore width/size of activated carbon microspheres (ACMSs) with diameter in a range of 2.7 ± 0.54 to 9.45 ± 1.81 μm and average pore width in a range of 1.60 to 2.0 nm on the electrochemical impedance characteristics of carbon-carbon symmetrical supercapacitors. Both the size and pore width/size of the ACMSs have negligible effects on contact resistance. The activation energy for the migration/diffusion of electrolyte ions in the supercapacitors made from the ACMSs of nearly same porous structure increases nonlinearly with the increase of the average size of the ACMSs, which is likely associated with overscreening effect. The activation energy for the migration/diffusion of electrolyte ions in the supercapacitors made from the ACMSs of nearly same size increases first and then decreases as the pore width/size increases.

Electrochemical characteristics of heterogeneous bipolar membranes and electromembrane process of recovery of nitric acid and sodium hydroxide from sodium nitrate solution

Frequency spectra of electrochemical impedance and current-overvoltage characteristics of an MB-2m bipolar membrane containing ion-polymer with catalytically active phosphoric acid groups in water dissociation reaction, and industrial MB-1, MB-2, and MB-3 bipolar membranes were studied in a system containing nitric acid and sodium hydroxide solutions. It is shown that the electrical resistance and overvoltage of bipolar region in the modified MB-2m and industrial MB-3 membranes are close and significantly lower than in industrial MB-1 and MB-2membranes. The effective rate constants of catalytic reaction of water dissociation are determined in the studied membranes. The process of producing nitric acid and sodium hydroxide from sodium nitrate with the modified MB-2m bipolar membrane and industrial MB-1 and MB-3 bipolar membranes was studied. It is shown that the use of the MB-2m bipolar membrane allows producing nitric acid and sodium hydroxide with higher concentrations, current efficiencies, specific productivity, lower specific energy consumption, and degree of sodium nitrate contamination than in the case when using industrial MB-1 and MB-3 membranes.

Synthesis and Characterization of TiO2 thin film Electrode based Dye Sensitized Solar Cell

Dye-Sensitized Solar Cells (DSSCs) are prominent alternative devices to conventional p-n junction silicon based solar cells because of their low fabrication cost and high power conversion efficiency, good cost/efficiency ratio. In the present work, DSSC devices were made-up with fluorine doped tin oxide (FTO) glass substrate, a TiO2 compact layer was deposited on FTO, Ruthenium(II) dye (N719), an iodide - triiodide electrolyte and a platinum (Pt) counter electrode. Photo anode with thin film layers of TiO2 and Pt counter electrode (photo-cathode) were prepared. Field emission electron microscope (FESEM) was employed to investigate the surface morphology of TiO2 layers. The DSSC device efficiency was evaluated by J-V characteristics. Fabricated devices were exhibited high power conversion efficiencies. The electrochemical impedance characteristics were analyzed by fitting the experimental results to the corresponding electrical equivalent circuit simulated data.

Alteration of surface pressure of macromolecular monolayer at the air-water interface and electrochemical impedance characteristics

Proteins are very important biological macromolecules, specific in their functions essential for many biological activities. Proteins are among the most vital components of all living matters with thousands of different types, and they are very specific in their nature which makes them important for usage in many biotechnological, biomedical, and food processing applications. Langmuir monolayer studies provide the characteristics of monolayer at the air-liquid interface. Langmuir monolayer of protein is affected by the molecular weight, macromolecular structure, denaturation and its purity. The interaction of the protein with other molecules greatly affects the behaviour of monolayer. Coconut oil layer at the air-water interface was prepared with different sub-phases including casein protein and whey protein. Wilhelmy plate measurement technique has been used to measure the surface pressure of the monolayer at the air-liquid interface. Experiments were carried out to study the stability using electrochemical impedance measurements. The electrostatic forces dominated the coconut oil - protein interaction, and the interface of macromolecules were controlled by expansion and compression. The macromolecules were adsorbed with a preferential orientation at the interface, and the stability of colloidal dispersions was governed by the intermolecular interactions. The stability using electrochemical impedance spectroscopy on the selected protein macromolecules along with other analysis were performed by varying various parameters.

Fabrication of anode-supported thin BCZY electrolyte protonic fuel cells using NiO sintering aid

A thin and fully dense BaCe0.6Zr0.2Y0.2O3-δ (BCZY) electrolyte for the use of anode-supported protonic fuel cells has been successfully prepared by spin coating using NiO sintering aid. The effects of NiO addition on the electrolyte microstructures and fuel cell performances are also investigated. An appropriate NiO addition has a significant positive contribution to the densification and grain growth of thin BCZY electrolytes. However, too much NiO addition gives rise to NiO aggregation in BCZY electrolyte and deteriorates the cell performance. The enhanced sintering mechanism can be mainly attributed to the oxygen vacancies generated from the NiO decomposition and bulk diffusion of Ni into BCZY perovskites. The fuel cell with a BCZY-3%NiO electrolyte exhibits the highest maximum power density of ~106.6 mW/cm2 at 800 °C among all fuel cells in this study. The electrochemical impedance characteristics of thin BCZY electrolyte fuel cells are further discussed under open circuit conditions.