Measurement of Impedance of AGM Solar Battery for RAPS Applications

The paper deals with the measurement of the cell impedance parameters during discharging and charging of the AGM 200Ah 6V Sun Power lead acid battery. Real and imaginary part of impedance of the battery were measured by PEIS method. Results of the impedance changes during discharging and charging were plot to Nyquist diagrams. Important values - ohmic resistance RS, charge transfer resistance RCT, double layer capacity CDL and Warburg coefficient σ were found during discharging and charging of the solar battery.

Analysis of adsorption of carbon steel corrosion inhibitor in model stratum waters by polylogarithmic isotherm

Using the methods of gravimetry, potentiodynamic polarization, and impedance spectroscopy, the protective effectiveness of the inhibitory composition INCORGAZ-111 with respect to hydrogen sulfide corrosion of carbon steel St3 in NACE and Samotlor oil field model stratum waters has been studied. Surface coverage is determined on the basis of the electric double layer capacity in presence of the inhibitor. Its adsorption is interpreted using the polylogarithmic isotherm with a big energy gradient of adsorption centers, that indicates linear energy heterogeneity of the surface. The constants of adsorption equilibrium, the energy gradient and the energy dispersion of adsorption centers as well as adsorption free energy were calculated.

Numerical Investigation of PEMFC Short-Circuit Behaviour Using an Agglomerate Model Approach

With increasing interest in clean energy generation in the transportation sector, increasing attention has been given to polymer-electrolyte-membrane fuel cells as viable power sources. One issue, the widespread application of this technology faces, is the insufficient knowledge regarding the transient behaviour of fuel cells, for instance, following a short-circuit event. In this paper, an agglomerate model is presented and validated, which enables the transient simulation of short-circuit events to predict the resulting peak current and discharge of the double layer capacity. The model allows for the incorporation of detailed morphological and compositional information regarding all fuel cell components. This information is used to calculate the reaction rate, diffusional and convectional species transfer, and the momentum transport. It can be shown that the charge in the double layer capacitance of the fuel cell is key to predicting the peak current and its charge is dependent on the operating conditions of the fuel cell. Further, the effects of the magnitude of the double layer capacity, current rise time and stoichiometry on the dynamic behaviour of the fuel cell are investigated. It can be shown that the discharge of the double layer capacity proceeds from the membrane through the catalyst layer to the gas diffusion layer and that the stoichiometry of the gas supply does not significantly change the absolute peak value of the short-circuit current.

Carbon materials obtained by carbonization of electrochemically gelled alginates and chitosan for supercapacitors

The aim of this work is to investigate the capacitive characteristics of carbon-based materials obtained by carbonization of electrochemically synthesized gels based on alginate (CA-i, CA-3i, CA-3n), chitosan (CH-i), as well as their composites (CHA-i) using cyclic voltammetry at different polarization rates. The capacitance characteristics of the examined materials were tested in 6M KOH and 0.5M H2SO4, The specific capacities of the tested materials, in an acidic medium, at a polarization rate of 2 mV / s, decrease according to the following sequence: C-A-i> C-HA-i> C-A-3i> C-A-3n> C-H-i, where the maximum value of the specific capacity is 362 F / g. Also, based on the obtained results, a large decrease in capacity was observed, accompanied by an increase in the speed of polarization of the working electrode. The capacitance properties were successfully separated using the Trasatti and Dunn methods, and the results of both methods are largely consistent. It has been shown that the dominant form of energy storage through Faraday reactions, ie the share of pseudocapacitance, is large in all materials. The highest share of double-layer capacity in acidic medium was recorded in C-H-i, while in the base medium the largest share of double-layer capacity was present in material C-A-3n, due to the fact that electrochemical activity of surface groups (oxygen and / or nitrogen) is pH-dependent.

Isoconductivity method to study adhesion of yeast cells to gold electrode

In this paper, we used impedance spectroscopy and gold electrodes to detect the presence of yeast cells and monitor the attachment of these cells to the electrodes. We analyzed the effect of conductivity changes of the medium and the attachment on the electrode-electrolyte interface impedance. A three-electrode cell was designed to produce a uniform electric field distribution on the working electrode and to minimize the counter electrode impedance. Moreover, we used a small AC overpotential (10 mV) to keep the system within the linear impedance limits of the electrode-electrolyte interface. This study proposes a new method to differentiate the impedance changes due to the attachment of yeast cells from those due to conductivity changes of the medium. The experiments showed that when the difference between the cell suspension and base solution conductivities is within the experimental error, the impedance changes are only due to the attachment of yeast cells to the electrodes. The experiments also showed a strong dependence (decrease) of the parallel capacity of the electrode electrolyte interface with the yeast cell concentration of suspension. We suggest that this decrease is due to an asymmetrical redistribution of surface charges on both sides of cell, which can be modeled as a biologic capacity connected in series with the double layer capacity of the interface. Our results could help to explain the rate of biofilm formation through the determination of the rate of cell adhesion.

Reference-Electrode Free pH Sensing Using Impedance Spectroscopy

We present a reference-electrode free sensor able to measure both pH and conductivitybased on impedance spectroscopy. The electrode is made of a layer of indium-tin-oxide (ITO). Theimpedance of this electrode at low frequencies depends on its double layer capacity, which varieswith pH due to modification of oxide groups at the ITO surface. At high frequencies, the impedanceis determined by the resistance in the system, which corresponds to the inverse conductivity of thesolution. Because no reference electrode is needed for this technique, miniaturization of the pHsensor is simple. We demonstrate a proof-of-principle experiment of the sensor for human plasmapH measurements.

The study of capacitive deionization behavior of a carbon nanotube electrode from the perspective of charge efficiency

In this work, the capacitive deionization (CDI) performance of a single-walled carbon nanotube (CNT) electrode has been studied from the point view of charge efficiency theory. It is revealed here that the charge efficiency of a CNT electrode is strongly dependent upon the cell voltage and solution concentration. Either the high cell voltage or the low ionic strength results in a high charge efficiency, implying that CDI is expected to be a promising technique for an aqueous solution with low ionic strength. Additionally, it is found that the high decay constant and high electrical double-layer capacity are beneficial to enhance electrosorption performance.