Effect of thorium on the reactions of iron(II) and iron(III) at a platinum electrode

1970 ◽  
Vol 48 (12) ◽  
pp. 1934-1936 ◽  
Author(s):  
J. H. Breckenridge ◽  
W. E. Harris
Keyword(s):  
Double Layer ◽  
Electrode Surface ◽  
Active Sites ◽  
Platinum Electrode ◽  
Exchange Current ◽  
Primary Effect ◽  
Current Voltage

The effect of thorium perchlorate on the iron(III)–iron(II) couple was studied by the use of current–voltage data and chronopotentiometry. It is suggested that the primary effect of thorium on the ferric–ferrous couple is exclusion of iron from the double layer and the blocking of active sites on the electrode surface with a resultant decrease in the exchange current for the iron couple.

Comparison of Gold and Platinum Electrode Responses in Activated Sludge

1993 ◽  
Vol 28 (11-12) ◽  
pp. 473-480
Author(s):  
A. Heduit ◽  
B. Martin ◽  
I. Duchamp ◽  
D. R. Thevenot
Keyword(s):  
Electron Transfer ◽  
Activated Sludge ◽  
Gold Electrode ◽  
Platinum Electrode ◽  
Electrochemical Determination ◽  
Exchange Current ◽  
Experimental Conditions ◽  
Equilibrium Exchange ◽  
Prolonged Contact ◽  
Current Densities

Gold and platinum were compared to ascertain how they expressed a stabilized potential in activated sludge. The comparison was based on electrochemical determination of the electron transfer rate (i.e. equilibrium exchange current density) and recording of potentials against time. When both metals are treated in the same way, platinum gives equilibrium exchange current densities approx. 10 times higher than gold, both in aerated activated sludge and in treated water. For platinum, the equilibrium exchange current densities range from 0.1 to 0.25 µA/cm2 immediately after polishing and decrease during prolonged contact with activated sludge subjected to alternating aeration/anoxia sequences. The lower kinetics of electron transfer on gold go together with significant differences in response:- In an aerobic medium a gold electrode potential is lower than that of a platinum electrode. In a strongly anaerobic medium, the reverse is true. Consequently, the amplitude of the potential variation between aerobic and anaerobic media is smaller for gold than for platinum. Under our experimental conditions this amplitude was approx 350 mV for gold and 850 mV for platinum.- The slopes of the linear relationships between potential and pH or potential and the logarithm of the dissolved oxygen concentration are two or three times greater for platinum than for gold. Although the values obtained with platinum electrodes cannot represent a veritable equilibrium state, the platinum electrode zero-current potential would seem to be far more sensitive to variations in the medium than that of the gold electrode; it is, therefore, more suitable for use in activated sludge.

Preparation of Fe/N co-doped hierarchical porous carbon nanosheets derived from chitosan nanofibers for high-performance supercapacitors

2021 ◽  
pp. 1-16
Author(s):  
Yaqi Yang ◽  
Ziqiang Shao ◽  
Feijun Wang
Keyword(s):  
Specific Surface ◽  
Specific Capacitance ◽  
Surface Area ◽  
Double Layer ◽  
Specific Surface Area ◽  
Porous Carbon ◽  
Active Sites ◽  
Transport Pathway ◽  
Carbon Nanosheets ◽  
Hierarchical Porous

Abstract Due to the low specific capacitance and small specific surface area of conventional carbon materials used as electrode materials for double-layer capacitors, the search for more ideal materials and ingenious preparation methods remains a major challenge. In this study, fractional porous carbon nanosheets were prepared by co-doping Fe and N with chitosan as nitrogen source. The advantage of this method is that the carbon nanosheets can have a large number of pore structures and produce a large specific surface area. The presence of Fe catalyzes the graphitization of carbon in the carbon layer during carbonization process, and further increases the specific surface area of the electrode material. This structure provides an efficient ion and electron transport pathway, which enables more active sites to participate in the REDOX reaction, thus significantly enhancing the electrochemical performance of SCs. The specific surface area of CS-800 is up to 1587 m2 g−1. When the current density is 0.5 A g−1, the specific capacitance of CS-800 reaches 308.84 F g−1, and remains 84.61 % of the initial value after 10,000 cycles. The Coulomb efficiency of CS-800 is almost 100 % after a long cycle, which indicates that CS-800 has more ideal double-layer capacitance and pseudo capacitance.

scholarly journals Effect of Anodic Pretreatment on the Performance of Glassy Carbon Electrode in Acetonitrile and Electrooxidation of Para-substituted Phenols in Acetonitrile on Platinum and Glassy Carbon Electrode

2019 ◽  
Vol 65 (1) ◽  
pp. 133-138 ◽  
Author(s):  
László Kiss ◽  
Sándor Kunsági-Máté
Keyword(s):  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Electrode Surface ◽  
Platinum Electrode ◽  
Anodic Peak ◽  
Carbon Electrode ◽  
Substituted Phenols ◽  
Cyclic Voltammetric ◽  
Pretreatment Time

In the first part of the work electropolymerisation of phenol was studied at glassy carbon electrode. Rapid fouling of its surface indicated the formation of coherent poly(phenyleneoxide) layer which was demonstrated by the repeated cyclic voltammetric scans. Effect of anodic pretreatment potential in acetonitrile solvent was also investigated and the results showed that at potentials higher than 2 V glassy carbon electrode becomes deactivated. Preanodisation of glassy carbon electrode at 3 V in acetonitrile resulted in diminished anodic peak currents by phenols. It was due to the partial deactivation of electrode surface and its extent increased with the pretreatment time. The electrooxidation of para-substituted phenols (p-Cl-phenol, p-NO2-phenol, p-tertbutylphenol, p-methoxyphenol) in acetonitrile resulted in no fouling layer on platinum electrode and the peak currents were significantly higher than in the first scan of unsubstituted phenol in the same concentration. Glassy carbon deactivated continuously by repeating the scans due to the solvent and bonding of products on the surface.

scholarly journals Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Anis Allagui ◽  
Todd J. Freeborn ◽  
Ahmed S. Elwakil ◽  
Brent J. Maundy
Keyword(s):  
Cyclic Voltammetry ◽  
Double Layer ◽  
Time Domain ◽  
Electric Double Layer ◽  
Constant Current ◽  
Step Response ◽  
Current Voltage ◽  
The Time Domain ◽  
Double Layer Capacitors ◽  
Electric Double Layer Capacitors

Abstract The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal S s C behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance R s in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (R s , Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical R s C model. We validate our formulae with the experimental measurements of different EDLCs.

The Electroreduction of Substituted Benzofurazans

1972 ◽  
Vol 50 (2) ◽  
pp. 263-269 ◽  
Author(s):  
W. R. Fawcett ◽  
P. A. Forte ◽  
R. O. Loutfy ◽  
J. M. Prokipcak
Keyword(s):  
Electron Transfer ◽  
Molecular Orbital ◽  
Double Layer ◽  
Rate Constants ◽  
Hyperfine Splitting ◽  
Platinum Electrode ◽  
Hückel Theory ◽  
Layer Effect ◽  
Standard Rate ◽  
Anion Radicals

The electroreduction of 4- and 5-substituted benzofurazans was investigated at a platinum electrode in acetonitrile. Standard potentials for the reactions were linearly related to the energy of the lowest vacant molecular orbital as estimated by Hückel theory. Standard rate constants for electron transfer decreased as standard potentials in the series became more cathodic. This decrease is attributed to a double layer effect. No correlation was obtained between standard rate constants and observed hyperfine splitting constants for the anion radicals.

scholarly journals Protection of Brass in HCl Solution by L-Cysteine and Cationic Surfactant

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Milan B. Radovanovic ◽  
Zaklina Z. Tasic ◽  
Marija B. Petrovic Mihajlovic ◽  
Milan M. Antonijevic
Keyword(s):  
Sodium Dodecyl Sulfate ◽  
Electrode Surface ◽  
Active Sites ◽  
Inhibition Efficiency ◽  
Sodium Dodecyl ◽  
Inhibition Mechanism ◽  
Eds Analysis ◽  
Dodecyl Sulfate ◽  
Brass Surface ◽  
Hcl Solution

Electrochemical behavior of brass and inhibitory effect of L-cysteine in HCl solution are investigated using electrochemical techniques in addition to SEM-EDS analysis. Results show that inhibition efficiency depends on inhibitor concentration and immersion time of brass electrode in inhibitor solution. Electrochemical test results point to formation of Cu(I)-cysteine complex on the brass surface in chloride solutions with addition of different amounts of cysteine. The formed complex has an important role in inhibition of the corrosion process in the examined media because Cu(I)-cysteine significantly reduces dissolution of brass. Curves obtained in acidic solution in the presence of cysteine after pretreatment in sodium dodecyl sulfate (SDS) by cyclic measurements and potentiodynamic polarization measurements indicate intense inhibition of corrosion processes. Efficient inhibition of brass dissolution is result of formation of a stable protective layer on the brass surface after pretreatment of the electrode in SDS solution. The brass surface is modified in sodium dodecyl sulfate solution in order to increase cysteine adsorption on the electrode surface and to improve inhibition efficiency. Inhibition mechanism of cysteine includes adsorption on active sites on the electrode surface, which is confirmed by SEM-EDS analysis of brass. Adsorption of cysteine in hydrochloric acid solution obeys the Langmuir adsorption isotherm. Also, Gibbs free energy of adsorption has a value of −31.5 kJ/mol and indicates strong adsorption of cysteine on the electrode surface.

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