Voltammetric Study of N-Benzoylthiourea and Its N',N'-Disubstituted Derivatives as Possible Electrode Modifiers

1999 ◽  
Vol 64 (12) ◽  
pp. 1937-1952 ◽  
Author(s):  
Karl-Heinz Lubert ◽  
Lothar Beyer ◽  
Markus Guttmann
Keyword(s):  
Surface States ◽  
Carbon Surface ◽  
Carbon Electrodes ◽  
Potential Range ◽  
Carbon Paste ◽  
Oxidation Current ◽  
Irreversible Reduction ◽  
Voltammetric Behavior ◽  
Positive Scan ◽  
Morpholine Derivatives

The voltammetric behavior of N-benzoylthiourea (BTU) and some of its N',N'-disubstituted derivatives is studied using glassy carbon and carbon paste electrodes in ethanolic solution. Irreversible reduction of the compounds takes place in a potential range between -0.5 and -1.1 V, where carbon surface groups are reduced as well. The products formed by reductive cleavage of the C-N bond of the amide group are oxidized in the subsequent positive scan at +0.5 V. Irreversible oxidation of the thiocarbonyl group of BTU (or its derivatives) takes place at about +1.0 V followed further by an oxidation of its N',N'-dialkyl and morpholine derivatives at more positive potentials. Oxidation current at +0.8 V is only observed in the case of the N',N'-diphenyl derivative. The oxidation current at +1.0 V depends linearly on the concentration of BTU (or its derivatives) and is suitable for their electroanalytical determination with carbon electrodes. The experimental results are compared with electrochemical behavior of related compounds. Furthermore, the influence of carbon surface states is discussed. It was concluded that N',N'-disubstituted derivatives of the BTU can be employed as modifying agents for carbon electrodes applicable in the potential range from +0.7 to -0.5 V.

Comparative Electrochemical Study of Some Phenothiazines with Carbon Paste, Solid Carbon Paste and Glass-Like Carbon Electrodes

2000 ◽  
Vol 65 (6) ◽  
pp. 1014-1028 ◽  
Author(s):  
Robert V. Sandulescu ◽  
Simona M. Mirel ◽  
Radu N. Oprean ◽  
Simion Lotrean
Keyword(s):  
Modified Electrodes ◽  
Linear Sweep Voltammetry ◽  
Pharmaceutical Formulations ◽  
Oxidation Potential ◽  
Electrochemical Study ◽  
Carbon Electrodes ◽  
Potential Range ◽  
Solid Carbon ◽  
Carbon Paste ◽  
Linear Sweep

In order to obtain modified electrodes with phenothiazines and to develop electrochemical methods for their determination in pharmaceutical formulations, promazine maleate, promethazine maleate and levomepromazine, were studied by linear sweep voltammetry using different types of working electrodes: carbon paste, solid carbon paste and glass-like carbon electrodes. A comparative electrochemical study of the above mentioned pheno- thiazines was performed in aqueous-alcoholic solutions, investigating the influence of pH, ionic strength and concentration on the current-potential curves. Linear sweep voltammetry in potential range from -0.1 to +1.3 V revealed that the oxidation potential and the current, strongly depend on the type of electrode and pH, the best results being obtained in acid buffer (pH 1.0). The current intensity depending linearly on the concentration in the range of 2.5·10-5-5·10-4 M promazine maleate, 2.5·10-5-2.5·10-4 M promethazine maleate and 6.2·10-5-1.2·10-3 M levomepromazine permits the development of electroanalytical methods to determine these phenothiazines in pharmaceuticals. The electrochemical determination yielded results comparable with spectrophotometric methods. Linear sweep voltammetry of carbon paste electrodes modified by incorporation of phenothiazines opens the possibility to use them as mediators in the design of some enzyme selective electrodes.

scholarly journals Investigation of Corrosion Methods for Bipolar Plates for High Temperature Polymer Electrolyte Membrane Fuel Cell Application

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 235
Author(s):  
Nadine Pilinski ◽  
Claudia Käding ◽  
Anastasia Dushina ◽  
Thorsten Hickmann ◽  
Alexander Dyck ◽  
...  
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Corrosion Behaviour ◽  
Polymer Electrolyte Membrane ◽  
Carbon Surface ◽  
Potential Range ◽  
Bipolar Plates ◽  
Electrolyte Membrane ◽  
Fuel Cell Application

In this work, different methods and electrochemical set-ups were investigated in order to study the corrosion behaviour of bipolar plates (BPP) for high temperature (HT) polymer electrolyte membrane fuel cell application. Using confocal and scanning electron microscopy, it was shown that chemical and electrochemical aging significantly increases surface roughness as well as morphology changes, confirming material degradation. Identical electrochemical corrosion behaviour was observed for both set-ups with typical quinone/hydroquinone peaks in the potential range ~0.6–0.7 V versus reversible hydrogen electrode (RHE). The appearance of the peaks and an increase of double layer capacitance can be related to the oxidation of carbon surface and, consequently, material corrosion. Simultaneously, an optimised corrosion set-up was introduced and verified regarding suitability. Both investigated set-ups and methods are useful to analyse the oxidation behaviour and corrosion resistance.

Quinone/hydroquinone redox couple as a source of enormous capacitance of activated carbon electrodes

2013 ◽  
Vol 1505 ◽  
Author(s):  
Krzysztof Fic ◽  
Mikolaj Meller ◽  
Grzegorz Lota ◽  
Elzbieta Frackowiak
Keyword(s):  
Activated Carbon ◽  
Redox Reactions ◽  
Electrode Materials ◽  
Activated Carbons ◽  
Hydroxyl Group ◽  
Carbon Surface ◽  
Carbon Electrodes ◽  
Main Subject ◽  
Solution Ph ◽  
Reversible Redox

ABSTRACTThe main subject of this paper is to examine and to evaluate the capacitive behaviour of activated carbon electrodes electrochemically decorated by quinone-type functional groups. For this purpose, different electrolytes, i.e. hydroquinone, catechol and resorcinol at the concentration of 0.38 mol L-1, dissolved in 1 mol L-1 H2SO4, 1 mol L-1 Li2SO4 and 6 mol L-1 KOH were used. These electrolytes could generate electroactive groups (able to undergo reversible redox reactions) on the surface of electrode material. Apart from typical adsorption of the mentioned dihydroxybenzenes, so called grafting could occur and might cause generation of quinone|hydroquinone functionals on carbon surface. As an effect of functional reversible redox reaction, additional capacitance value, called pseudocapacitance, could be achieved. Hence, besides typical charge originating from charging/discharging of the electrical double layer on the electrode/electrolyte interface, additional capacitance comes also from faradaic reactions. Activated carbons are the most promising electrode materials for this purpose; apart from great physicochemical properties, they are characterized by well-developed specific surface area over 2000 m2 g-1 which results in high capacitance values.In the manuscript the influence of the hydroxyl group location as well as electrolyte solution pH on the electrochemical performance of the electrode is discussed.

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