Supercapacitors Fabrication and Performance Evaluation Techniques

Supercapacitors have surfaced as a promising technology to store electrical energy and bridge the gap between a conventional capacitor and a battery. This chapter reviews various fabrication practices deployed in the development of supercapacitor electrodes and devices. A broader insight is given on the numerous electrode fabrication techniques that include a detailed introduction, principles, pros and cons, and their specific applications to provide a holistic view. Key performance parameters of an energy storage device are explained in detail. A further discussion comprises several electrochemical measurement procedures that are used for the supercapacitor performance evaluation. The performance characterization section helps to determine the correct approach that should be utilized for supercapacitor device performance measurement and assessment.

Electrochemical Measurement System for Chlorides in Drinking and Wastewater

This paper presents a system for the measurement of chlorides in drinking and wastewater, based on an electrochemical process using a selective electrode as a transducer, which was developed by this group. The measurement for the concentration is carried out by introducing the implemented electrode (considered as reference) in the sample that will be analyzed; then a current is passed producing a potential difference in the system. Different aqueous solutions of sodium chloride (NaCl) were used, ranging between 35 and 3546 µg of chloride ions (Cl−). As a data acquisition and monitoring system for the analysis, an ATmega 328P microcontroller was used as the main capture element for subsequent interpretation through graphics. The experimental results show that it was possible to detect a potential difference in the electrochemical measurement system that corresponded to 35 µg of chloride ions (Cl−), making clear the detection process and the selectivity of chloride ions. It is important to mention that with this measurement system and the applied methodology, results are obtained in real time using a small sample volume and without generate ng extra liquid waste, compared to the application of the traditional analytical titrimetric method. Finally, this chloride measurement system is inexpensive and can be used in drinking and wastewater measurements.

Review—Concentration Measurements In Molten Chloride Salts Using Electrochemical Methods

The electrochemical measurement of concentration in molten chloride salts is a valuable tool for the control of existing and potential industrial processes, recycling of precious materials and energy production. The electrochemical techniques commonly used to measure concentration and each techniques’ associated theory are discussed. Practices which improve measurement accuracy and precision are set forth. Exceptionally accurate and precise measurements published in the literature are evaluated based on their performance in specified concentration ranges. The strengths and weaknesses of the most accurate measurements are briefly explored. Chronopotentiometry (CP) and square wave voltammetry (SWV) are accurate and precise with low concentration measurements. SWV was accurate at low concentrations, even in multi-analyte mixtures. CP was accurate for only single analyte mixtures. Open-circuit potentiometry (OCP) is accurate and precise in single-analyte mixtures but yields large errors in multianalyte mixtures. Cyclic voltammetry (CV), chronoamperometry (CA) and normal pulse voltammetry (NPV) are accurate and precise across all concentration ranges. NPV is exceptionally well suited for measurements in melts with multiple electroactive species.

A Pencil-Lead Immunosensor for the Rapid Electrochemical Measurement of Anti-Diphtheria Toxin Antibodies

Diphtheria is a vaccine-preventable disease, yet immunization can wane over time to non-protective levels. We have developed a low-cost, miniaturized electroanalytical biosensor to quantify anti-diphtheria toxin (DTx) immunoglobulin G (anti-DTx IgG) antibody to minimize the risk for localized outbreaks. Two epitopes specific to DTx and recognized by antibodies generated post-vaccination were selected to create a bi-epitope peptide, biEP, by synthesizing the epitopes in tandem. The biEP peptide was conjugated to the surface of a pencil-lead electrode (PLE) integrated into a portable electrode holder. Captured anti-DTx IgG was measured by square wave voltammetry from the generation of hydroquinone (HQ) from the resulting immunocomplex. The performance of the biEP reagent presented high selectivity and specificity for DTx. Under the optimized working conditions, a logarithmic calibration curve showed good linearity over the concentration range of 10−5–10−1 IU mL−1 and achieved a limit of detection of 5 × 10−6 IU mL−1. The final device proved suitable for interrogating the immunity level against DTx in actual serum samples. Results showed good agreement with those obtained from a commercial enzyme-linked immunosorbent assay. In addition, the flexibility for conjugating other capture molecules to PLEs suggests that this technology could be easily adapted to the diagnoses of other pathogens.

Flexible Film-Type Sensor for Electrochemical Measurement of Dopamine Using a Molecular Imprinting Method

Neurotransmitters, which are responsible for the signal transduction of nerve cells in the brain, are linked not only to various emotions and behaviors in our daily life, but also to brain diseases. Measuring neurotransmitters in the brain therefore makes a significant contribution to the progress of brain science. The purpose of this study is to develop a flexible thin film-type sensor that can electrochemically measure dopamine (DA) selectively and with high sensitivity. The thin-film sensor was prepared by printing gold colloidal ink on a polyimide film with a thickness of 25 µm—which the most flexible of the films examined that could maintain the buckling load (1 mN) required for insertion into the brain. The electrode (DA-PPy electrode) was then prepared by electropolymerization of polypyrrole (PPy) using DA as a template. The flexural rigidity of the sensor was 4.3 × 103 nNm, which is the lowest of any neurotransmitter sensors reported to date. When a DA solution (0–50 nM) was measured with the DA-PPy electrode using square-wave voltammetry (SWV), the slope of the calibration curve was 3.3 times higher than that of the PPy only negative control electrode, indicating an improvement in sensitivity by molecular imprinting with DA. The sensor was used to measure 0−50 nM norepinephrine (NE) and serotonin (5-HT), and the slope of the DA calibration curve at 0.24 V (19 ± 4.4 nA/nM) was much greater than those of NE (0.99 ± 3.3 nA/nM) and 5-HT (2.5 ± 2.4 nA/nM) because the selectivity for DA was also improved by molecular imprinting.

Effect of Glutaraldehyde on Corrosion of X80 Pipeline Steel

Glutaraldehyde (GA) is widely employed as a biocide to control microbiologically influenced corrosion in oil fields and industrial water treatment. It might be corrosive to metal. In this study, the effect of glutaraldehyde on the corrosion behavior of X80 pipeline steel was investigated using electrochemical measurement, weight-loss tests and scanning electron microscope (SEM). The weight-loss and electrochemical data show that GA accelerates the corrosion of samples under aerobic conditions, but just slightly influences the corrosion of steel under anaerobic conditions. The results showed that the glutaraldehyde has a minor effect on the corrosion of steel under anaerobic conditions.

Effect of Service Environmental Parameters on Electrochemical Corrosion Behavior of L80 Casing Steel

The corrosion behavior of L80 casing steel was studied in a simulating annulus environment using the electrochemical measurement method, immersion test, and tensile test under a high-temperature and high-pressure H2S/CO2 environment. The partial pressure of CO2 (PCO2), the partial pressure of H2S (PH2S), water content, and preloading stress remarkably affected the corrosion behavior of L80 steel. The influence of PCO2 on stress corrosion cracking (SCC) susceptibility has an inflection point of approximately 1.1 MPa. The SCC susceptibility reaches the maximum when the PCO2 is about 1.1 MPa. The SCC susceptibility has a positive correlation to PH2S and water content. The higher water content of the corrosion medium can increase the electrical conductivity of the corrosion medium and promote the corrosion of L80 steel, which can improve the diffusion of hydrogen into steel and promote the SCC of L80 steel. Preloading stress can promote local corrosion, thereby promoting SCC of steel under stress. The dislocation emergence point caused by preloading stress can accelerate the diffusion of hydrogen into steel and increase SCC susceptibility.

Effect of Acidizing Process on the Stress Corrosion Cracking of HP-13Cr Stainless Steel in the Ultra-depth Well Environment

The effect of acidizing process on the stress corrosion cracking of HP-13Cr stainless steel in the ultra-depth well environment was studied by the slow strain rate test, the electrochemical measurement, the microstructure observation, and the finite element modeling. The results indicated that the acidizing process significantly increased the stress corrosion cracking susceptibility of HP-13Cr stainless steel and induced the fracture mode to the brittle characteristic in the high temperature and CO2 pressure environment. The stress corrosion cracking susceptibility also increased with the increase of temperature and CO2 pressure. There were dense defects including pits and cracks in the fracture section from the transverse view. After the acidizing process, under tensile stress condition, the increasing roughness will cause the stress concentration and promote the local anodic dissolution, which induces the initiation of stress corrosion cracking.

EFFECT OF FLOW RATE AND TEMPERATURE ON CORROSION RATE OF CARBON STEEL PIPE IN CONDENSATE SOLUTION FROM GEOTHERMAL POWER PLANT

The research aims to study the effect of flow rate and temperature on corrosion rate of carbon steel pipe in condensate solution from geothermal power plant. The corrosion rate in this study highlighted by electrochemical measurement. Electrochemical measurement performed in two conditions i.e stagnant and dynamic conditions. There are three kinds of temperature used in this research : 30oC, 40oC, and 50oC. Modification of corrosion cell installed for dynamic condition with flow rate variations : 0.27 m/s; 0.6 m/s; 1 m/s; 1.5 m/s; and 1.9 m/s. It was found that corrosion rate boosts with temperature and fluid flow rate in condensate solution of geothermal power plant. The highest corrosion rate (38 mpy) obtained at 50oC and 1.9 m/s of flow rate.