No abstract

In this work we present the comparison among three glassy carbon electrodes modified by Co-porphyrin (CoTAPP), orthophenylendiamine (OPD), or both, simultaneously. This comparison shows the differences among their electrochemical behavior and their electrocatalytic behavior toward the oxidation of sulfite. In the case of the glassy carbon modified electrodes, the presence of the copolymer enhances the electrocatalytic performance of the modified electrodes in spite of the non-catalytic response (compared to the bare glassy carbon) of both homopolymersmodified electrodes toward the oxidation of sulfite. Also, the oxidation of sulfite extracted from red wine is showed. The copolymer-modified electrode is capable of oxidizing the extracted free sulfite in a 0.02 M NaOH solution. Through the addition of standards method, a concentration of 44 ppm for free sulfite is found in a Chilean red wine.Electrodes modified by polymers derived from aniline are widely studied because of their broad application range. Among them, ortho-phenylenediamine, OPD, has got a considerable amount of attention as an electropolymer. This polyOPD polymer happens to be conductive, can be electrochemically synthesized in acid dissolutions and presents a voltammetric response that shows that there is only one reversible redox couple[1]. On the other hand, the electropolymer is stable in acid, neutral, and basic dissolutions, and exposed to air [2]. To study the mechanism of electropolymerization, characterize the polymer film and discover different applications of polyOPD [6], several electrochemical techniques were used [1], resonance Raman spectroscopy [3], scanning electron microscopy [4], electrochemical impedance spectroscopy (EIS) [5], and other methods. Further, it was achieved the electropolymerization of porphyrins from different transition metals [7] such as Co(II) para-tetra-aminophenyl porphyrin, CoTAPP [8][9][10][11][12][13], for the obtaining of modified electrodes active on oxidation of sulfite. However, the films formed are fragile, unstable and very thin [14].Simultaneous polymerization of OPD and CoTAPP dissolved in an acid solution generates a copolymer in which the qualities of both monomers are enhanced, obtaining a film that is stable and has high electrocatalytic activity [15]. There is abundant literature about electroactive copolymers, indicating the great interest about them, because of their wide variety of applications on sensors, biosensors, rechargeable batteries, corrosion inhibitors, molecular electronic devices, electromagnetic 10.1149/06401.0037ecst ©The Electrochemical Society ECS Transactions, 64 (1) 37-42 (2014) 37 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-15 to IP ECS Transactions, 64 (1) 37-42 (2014) 41 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-05-15 to IP

No abstract

No abstract

Glassy carbon electrodes modified with cobalt(ii) octaethylporphyrin capable of catalyzing hydrazine oxidation at low overpotentials.

In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.

In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF 6 ) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF 6 . These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported.

No abstract