scholarly journals The effect of pyridine on the electrochemical parameters of the hydroxonium discharge at the copper cathode

2019 ◽  
Vol 60 (12) ◽  
pp. 62-69
Author(s):  
Alexander V. Kolesnikov ◽  
◽  
Egor I. Ageenko ◽  
Keyword(s):  
Sulfuric Acid ◽  
Reaction Order ◽  
Silver Chloride ◽  
Reference Electrode ◽  
Electrode System ◽  
Constant Current ◽  
Transfer Coefficients ◽  
Potential Region ◽  
Average Data ◽  
Hydroxonium Ion

In this work, we studied the electrochemical reduction of hydrogen (hydroxonium ion) from acidic aqueous solutions in the presence of a surface active substance – pyridine. H2SO4 (r.h.) was used as a reagent to study the discharge of hydroxonium cations. The effect of pyridine on the reduction of hydrogen cations was carried out in solutions of sulfuric acid (0.09; 0.18; 0.36 M) with pyridine additives from 1.4·10-3 to 8.4·10-3 M. Potentiostatic studies were performed on a Potentiostat P-30Jcom Elins using a three-electrode cell. The working electrode (cathode) was made of M1 grade copper with an area of 0.09 cm2; auxiliary (anode) – from a platinum plate with an area of 0.20 cm2, the reference electrode is silver chloride (AgCl/Ag). The results are presented according to the average data obtained during 30 s of electrolysis in the potential region (-950-1100 mV for AgCl/Ag), with potentiometric measurements. The results are presented by the average data obtained in the initial 5 s of the process, in studies in the galvanostatic mode at current densities from 0 to 110 mV/cm2. An increase in the constant current of load almost to a small extent influenced the change in overvoltage with time, as shown by galvanostatic studies. Overvoltage, on average, decreased from 3-6 to 1-2 mV in the first 5 seconds of the beginning of the process, during the study with or without pyridine. Overvoltage ceased to depend after 10-15 s on the time of galvanostation. The effect of the addition of pyridine to the electrolyte was studied and it was shown that the negative effect of pyridine on the discharge of the hydroxonium ion increases with increasing acidity of the electrolyte. An increase in the density of exchange currents with a decrease in the content of sulfuric acid in the electrolyte is noted, which is associated with the approach of the electrode system to the equilibrium state. The decrease in the transfer coefficients of the hydrogen discharge reaction with an increase in the acid of content in the electrolyte and pyridine additives was explained by the distant position of the transition state localization from the electrode surface. The calculations of the reaction order for the hydroxonium ion in the presence and absence of pyridine in the electrolyte are presented. The obtained value of the reaction order, taking into account standard errors close to unity, allows us to conclude that at the initial stage, the hydroxonium of molecule is discharged, the products of which are atomic hydrogen, the HSO4 anion and water. In the kinetics of the process of the discharge of hydrogen cations, the stages can further play an important role: surface diffusion of hydrogen ad-atoms, formation of gas bubbles and their desorption, adsorption of hydrogen by metal.

scholarly journals Discharge of hydronium ions on metal cathodes in the presence of pyridine

2020 ◽  
Vol 63 (8) ◽  
pp. 58-63
Author(s):  
Alexander V. Kolesnikov ◽  
◽  
Egor I. Ageenko ◽  
Keyword(s):  
Sulfuric Acid ◽  
Acid Content ◽  
Transfer Coefficients ◽  
Discharge Current Density ◽  
Average Data ◽  
Hydronium Ions ◽  
Hydronium Ion ◽  
Lead Electrode ◽  
Hydrogen Discharge ◽  
Sulfuric Acid Content

In this work, studies have been carried out on the electrochemical reduction of hydrogen (hydronium ion) from acidic aqueous solutions in the presence of an organic substance – pyridine. Electrolysis was carried out in an electrolyte with a sulfuric acid content (0.18; 0.36 M) with a pyridine additions of 8.4·10-3 M. Potentiostatic studies were carried out on a Potentiostat P-30Jcom Elins potentiostat using a three-electrode cell. Working electrodes (cathodes) were made of M1 copper with an area (S) of 0.09 cm2; aluminum (AD1) S – 0.125 cm2, zinc (Ts0A) S – 0.35 cm2, lead (Cl) S – 0.20 cm2, auxiliary (anode) – from a platinum plate with an area of 0.20 cm2, reference electrode – silver chloride (AgCl/Ag). In potentiometric measurements, the results are presented according to the average data obtained for 30 s of electrolysis in the potential range (-950 ÷ -1100 mV for AgCl/Ag), and in studies in the galvanostatic mode at current densities from 0 to 110 mV/cm2, the results are presented as average data, obtained in the initial 5 s of the process. The paper presents comparative data on the electrokinetic parameters studied under the same conditions of hydrogen discharge reactions at different cathodes in electrolytes with a sulfuric acid content of 0.36 M. It is shown that the highest discharge current density of the hydronium ion (Н3О+) is achieved at the copper electrode, and the lowest at the lead electrode. With the addition of 8.4∙10-3 M pyridine to the electrolyte, the reduction of hydrogen cations is somewhat reduced on the electrodes used, except for lead. The transfer coefficients of the hydrogen discharge at all electrodes are low, and with the addition of pyridine they decrease even more. The low transfer coefficients indicate that the process of the hydronium ion discharge proceeds in a non-activation mode. The lowest exchange current is recorded at the copper and lead electrode. At the zinc electrode, the exchange of current is one to two orders of magnitude higher than at the other electrodes, so it can be noted that at this electrode the system under consideration is closer to the equilibrium of state. The order of the reaction of the course of electrolysis by the hydronium cation on the copper, aluminum and zinc electrodes is close to unity. The addition of pyridine leads to a slight decrease in the order of the reaction. This is due to the fact that pyridine molecules in acidic solutions exist in the form of pyridinium ion, which is reduced at the cathode. In this case, a significant amount of hydrogen is absorbed, which should explain the decrease in the order of the reaction with respect to the hydronium ion in the presence of pyridine additives. The obtained low values of the transfer coefficients indicate that, during the discharge of hydronium ions, the process is limited to a greater extent by the concentration polarization. The diffusion nature of the reduction of hydronium ions in electrolytes with a sulfuric acid concentration of 0.18 and 0.36 M is also evidenced by data taken in a dynamic mode.

scholarly journals Investigation the effect of pyridine on the electrolysis of zinc from acidic and neutral solutions

2019 ◽  
Vol 57 (2) ◽  
pp. 60-67
Author(s):  
Alexander V. Kolesnikov ◽  
◽  
Irina V. Tsyganova ◽  
Keyword(s):  
Sulfuric Acid ◽  
Silver Chloride ◽  
High Current Density ◽  
Discharge Rate ◽  
Reference Electrode ◽  
Published Data ◽  
Transport Numbers ◽  
Priority Effect ◽  
Negative Effects ◽  
Current Sharing

The particular importance for the practice of zinc electrolysis is the knowledge of the reasons that affect the performance of this process. Previously published data indicate about the negative effects on the zinc current efficiency, energy consumption, quality of the cathode deposit non-optimal composition of the mixture of surfactant: licorice bone glue, lignosulfonate, flocculants, ekstragentami-2-ethyl-hexyl phosphoric acid (D2EHPA) various car oils, kerosene, white spirit, polyacrylamide. Electrochemical studies were performed using three electrolytes of the following composition: 0.25 M ZnSO4, 0.25 M ZnSO4 + 48 g/l H2SO4; 0.25 M ZnSO4 + 18 g/l H2SO4. Potentiostatic and galvanostatic studies were carried out on the potentiostat "Potentiostat P-30J com" by "Elins" using a three-electrode cell. The working electrode (cathode) is made of copper with an area of 0.1 cm2; the auxiliary electrode (anode) is made of a platinum plate with an area of 0.20 cm2, the reference electrode is silver chloride (AgCl/Ag). Measurements were carried out at room temperature under intensive stirring with a magnetic stirrer. Initially, before the removal of the experimental curves, zinc buildup at the cathode was carried out at a constant potential of -1200 mV (AgCl/Ag) for 5 min, using an electrolyte of 0.25 M ZnSO4. For potentiometric measurements, the results are presented by averaged data obtained for 30 seconds of electrolysis, and for galvanostatic measurements by 0.05 seconds from the beginning of electrolysis. In this article, we consider the effect of pyridine additives on the discharge of cations from zinc sulfate electrolytes, including sulfuric acid. The ratio in one of the three electrolytes of zinc mass to the mass of sulfuric acid corresponded to the composition of industrial solutions directed to the electrolysis of zinc. It is shown that the increase in the content of acid in the electrolyte, the increase in the cathode potential and the discharge rate of cations increases with the addition of pyridine decreases. The increase in the discharge rate of cations at low pyridine additives of 0.1 mg/l for electrolytes of the composition: 0.25 M ZnSO4 and 0.25 M ZnSO4 + 18 g/l H2SO4, and the decrease in discharge currents with the addition of 0.6 mg/l pyridine in the electrolysis of a solution containing 18 g/l H2SO4, compared with electrolysis without additives, testified to the priority effect of pyridine on the discharge of hydrogen cations. In the work it is noted, when removing dependencies with pyridine additives at the final stage, an accelerated increase in overvoltage occurs, and without the addition, the increase slows down. This is explained by the fact that the addition of pyridine, due to its ability to protonation and absorption of a significant amount of hydrogen, slows down the discharge of hydrogen to a greater extent than zinc in areas of high current density. It is shown that the final parts of the curves of the voltammograms, the current sharing at high cathodic potentials increased almost nine-fold when the concentration of the pyridine up to 0.3 mg/l However, when the concentration of the pyridine up to 0.6 mg/l current sharing (i_o), as well as the rate of discharge of ions decreases, which is consistent with the equation of Butler-Folmer for the cathodic process at high voltages. The calculation of transport numbers has allowed concluding that at low transport numbers associated with the addition of pyridine, the function of the transition state Gibbs will increase, and the cation will be slower to approach the electrode because of the increased overvoltage. In this case, it is believed that the recovery reaction proceeds in the non-activation mode.

Facile and Fast Detection of Genistein in Derris scandens by Square Wave Voltammetry using a Cobalt(II) Phthalocyanine-Modified Screen-Printed Electrochemical Sensor

2020 ◽  
Vol 16 (3) ◽  
pp. 341-348
Author(s):  
Surinya Traipop ◽  
Suchada Chuanuwatanakul ◽  
Orawon Chailapakul ◽  
Eakkasit Punrat
Keyword(s):  
Electrochemical Sensor ◽  
Square Wave Voltammetry ◽  
Silver Chloride ◽  
Reference Electrode ◽  
High Sensitivity ◽  
Plastic Substrate ◽  
Fast Analysis ◽  
Square Wave ◽  
Wave Voltammetry ◽  
Screen Printed

Background: Recently, Derris scandens, a Thai herbal medicine with anti-inflammatory activity, is widely used as beverage and supplementary food. When the traditional medicine is a choice for health therapy, the simple and reliable equipment is required to control the suitable consuming amount of the active component. Objective: To develop the electrochemical sensor for genistein determination in Derris scandens with high sensitivity and rapid operation. Methods: An in-house screen-printed electrochemical sensor consisting of a three-electrode system was developed for genistein determination. A silver/silver chloride (Ag/AgCl) reference electrode, a carbon counter electrode and a carbon working electrode were prepared on a 0.3-mm-thick plastic substrate by the screen-printing technique using conductive ink. The dimensions of each sensor were 2.5×1.0 cm. Only 50 µL of sample solution was required on this device for the determination of genistein concentration by rapid response square wave voltammetry. Results: The oxidation peak of genistein appeared with good response in acidic media at a peak potential of 0.6 V. Moreover, the signal was enhanced by modifying the conductive carbon ink with cobalt( II) phthalocyanine. Under the optimized conditions, the linear range was found to be 2.5-150 µM and the detection limit was 1.5 µM. Moreover, the small volume extraction was successfully developed without any further pre-concentration. This proposed method was applied to determine genistein in Derris scandens with satisfying results. Conclusion: The proposed method is promising as an alternative method for genistein determination with facile and fast analysis.

New electrical stimulation technologies for sheep carcasses New electrical stimulation technologies for sheep carcasses

2005 ◽  
Vol 45 (5) ◽  
pp. 575 ◽  
Author(s):  
F. D. Shaw ◽  
S. R. Baud ◽  
I. Richards ◽  
D. W. Pethick ◽  
P. J. Walker ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
High Voltage ◽  
Consumer Satisfaction ◽  
Electrode System ◽  
Constant Current ◽  
Eating Quality ◽  
Meat Eating ◽  
Medium Voltage ◽  
Sheep Meat ◽  
Maximum Voltage

High voltage electrical stimulation applied to the lamb carcass at the end of the dressing procedure often leads to an improvement in overall product quality by reducing the incidence of toughness. It would be advantageous if the same results could be consistently achieved with the use of lower, safer, voltages — medium voltage electrical stimulation. Experiments were conducted to determine the effect of medium voltage electrical stimulation applied to wool-on carcasses on meat quality as assessed using the Sheep Meat Eating Quality protocols. A further experiment examined the interaction of electrical stimulation and meat aging time on the consumer acceptance of lamb meat. In the first experiment, 3 treatments: control (non-stimulated), medium voltage electrical stimulation (applied to the wool-on carcass) and high voltage electrical stimulation (applied at the completion of dressing) were examined. Samples of the loin (LTL) and rump (GM) muscles were evaluated by consumers using Sheep Meat Eating Quality protocols. For both muscles, the consumers gave higher scores for tenderness, juiciness, flavour and overall acceptability to the stimulated product (P<0.001). There were no statistically significant differences between the 2 stimulation treatments. The second experiment was conducted at a commercial lamb-processing abattoir that had installed a prototype automated electrode system designed to work at chain speed. Lambs received either no stimulation (control), low current medium voltage electrical stimulation (constant current 300 mA peak, 15 Hz, maximum voltage 550 V peak) or high current medium voltage electrical stimulation (constant current 600 mA peak, 15 Hz, maximum voltage 550 V peak) immediately after sticking. Electrical stimulation improved both the objective and sensory (Sheep Meat Eating Quality) eating quality attributes of lamb loin muscle when assessed following 2 days of ageing. When expressed according to consumer satisfaction rating, 30, 37 and 70% of the loins receiving low, high or no electrical stimulation, respectively, were rated as unsatisfactory at 2 days of ageing. At 4 days of ageing no loins from carcasses in the low stimulation treatment were rated by consumers to be unsatisfactory (P<0.05) compared with either non-stimulated (40%) or high-stimulated loins (35%). With respect to the effects of aging meat, electrical stimulation improved the consumer score at 2 days post-stunning by 8.9 and 4.7 points for tenderness and overall liking, respectively. Further linear improvements due to aging were similar for both electrical stimulation and unstimulated products. Under conditions of no electrical stimulation used in this experiment, 10 days aging results in tenderness and overall liking scores greater than 60 and with ES similar scores are achieved in 5 days. Consumer scores over 60 greatly reduce the chance of meat being classified as unsatisfactory.

scholarly journals Screen-printed Paper-based Three-electrode System with Long-term Stable and Instantaneously Usable Reference Electrode

2018 ◽  
Vol 47 (12) ◽  
pp. 1502-1504 ◽  
Author(s):  
Isao Shitanda ◽  
Masato Komoda ◽  
Yoshinao Hoshi ◽  
Masayuki Itagaki
Keyword(s):  
Reference Electrode ◽  
Electrode System ◽  
Screen Printed

An Automatic Polarization Apparatus for Electrochemical Corrosion Studies

CORROSION ◽  
1969 ◽  
Vol 25 (12) ◽  
pp. 515-519 ◽  
Author(s):  
W. D. HENRY ◽  
B. E. WILDE
Keyword(s):  
Cathodic Polarization ◽  
Reference Electrode ◽  
Electrochemical Corrosion ◽  
304 Stainless Steel ◽  
Constant Current ◽  
Voltage Source ◽  
Potential Range ◽  
Alloy Development ◽  
Corrosion Studies ◽  
Potentiodynamic Anodic Polarization

Abstract Statistical alloy development programs in which electrochemical screening techniques are used require facilities to produce precision polarization data. Conventional equipment and techniques presently available for such programs are not entirely satisfactory. Therefore, modifications were made to readily available commercial equipment to significantly improve the attainable sensitivity and reproducibility. This paper describes in detail the procedures necessary to produce an apparatus that automatically measures and records anodic and cathodic polarization curves over an applied potential range of ±2.0 volts. Traverse rates between 2 × 10−3 and 3 × 104 volts per hour are attainable and can be used to polarize electrodes through zero volts (with respect to reference electrode) without the necessity of manual switching. A special mode switch is described in detail with which the basic electronic potentiostat can be used as a constant current or constant voltage source by manual selection. The results obtained from three typical polarization experiments: (1) potentiodynamic anodic polarization, (2) galvanodynamic cathodic polarization, and (3) galvanodynamic linear polarization of AISI Type 304 stainless steel in hydrogen saturated 1N H2SO4 at 25 C (77 F), showed the performance of the apparatus to be equal to or superior to that of conventional manual procedures.

scholarly journals Two Electrode ECG And EOG System For Monitoring Applications

2019 ◽  
Vol 8 (11) ◽  
pp. 262-265
Keyword(s):  
Reference Electrode ◽  
Cost Effective ◽  
Electrode System ◽  
Ecg Signal ◽  
Biomedical Signal ◽  
Ecg Signals ◽  
Arm Position ◽  
The Stability ◽  
Electrocardiogram Ecg ◽  
Total Gain

Heart and Eye are two vital organs in the human system. By knowing the Electrocardiogram (ECG) and Electro-oculogram (EOG), one will be able to tell the stability of the heart and eye respectively. In this project, we have developed a circuit to pick the ECG and EOG signal using two wet electrodes. Here no reference electrode is used. EOG and ECG signals have been acquired from ten healthy subjects. The ECG signal is obtained from two positions, namely wrist and arm position respectively. The picked-up biomedical signal is recorded and heart rate information is extracted from ECG signal using the biomedical workbench. The result found to be promising and acquired stable EOG and ECG signal from the subjects. The total gain required for the arm position is higher than the wrist position for the ECG signal. The total gain necessary for the EOG signal is higher than the ECG signal since the ECG signal is in the range of millivolts whereas EOG signal in the range of microvolts. This two-electrode system is stable, cost-effective and portable while still maintaining high common-mode rejection ratio (CMRR).

scholarly journals Comparisons of formic acid oxidation at supported Pt catalyst and at low-index Pt single crystal electrodes in sulfuric acid solution

2003 ◽  
Vol 68 (11) ◽  
pp. 849-857 ◽  
Author(s):  
Amalija Tripkovic ◽  
Ksenija Popovic ◽  
Jelena Lovic
Keyword(s):  
Sulfuric Acid ◽  
Formic Acid ◽  
Single Crystal ◽  
Particle Diameter ◽  
Supported Catalyst ◽  
Pt Catalyst ◽  
Acid Oxidation ◽  
Potential Region ◽  
The Mean ◽  
Supported Pt Catalyst

The oxidation of formic acid was studied at supported Pt catalyst (47.5 wt%. Pt) and a low-index single crystal electrodes in sulfuric acid. The supported Pt catalyst was characterized by the TEM and HRTEM techniques. The mean Pt particle diameter, calculated from electrochemical measurements fits well with Pt particle size distribution determined by HRTEM. For the mean particle diameter the surface averaged distribution of low-index single crystal facets was established. Comparison of the activities obtained at Pt supported catalyst and low-index Pt single crystal electrodes revealed that Pt(111) plane is the most active in the potential region relevant for fuel cell applications.

Preparation and Electrochemical Characterization of Mn/Pb Composite Oxides for Supercapacitors

2007 ◽  
Vol 336-338 ◽  
pp. 470-473
Author(s):  
Zhian Zhang ◽  
Yan Qing Lai ◽  
Jie Li ◽  
Ye Xiang Liu
Keyword(s):  
Specific Capacitance ◽  
Electrochemical Characterizations ◽  
Amorphous Structure ◽  
Electrode System ◽  
Constant Current ◽  
Manganese Acetate ◽  
Composite Oxides ◽  
Constant Current Charge ◽  
Nano Size

Mn/Pb composite oxides were prepared by solid-state reaction by KMnO4 with manganese acetate and lead acetate at low temperature. The products were characterized by XRD and TEM. The results show that the composite oxides are nano-size and amorphous structure. Electrochemical characterizations were performed by cyclic voltammetry (CV) and constant current charge-discharge in a three-electrode system. The potential windows of Mn/Pb composite oxides electrode are increased. With increasing the ratio of Pb, the specific capacitance goes through a maximum at 20% mol Pb. The specific capacitance of pure MnO2 is 158 F/g and is improved to 180 F/g for the Mn0.8Pb0.2Ox composite oxide by constant current discharge.

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