No abstract

Electro-catalytic reduction of CO2 at −0.8 V vs. Ag/AgCl has been studied with poly-Co(ii)-porphyrin on ITO in BMImBF4 as reaction media.

Carbon dioxide is reduced to carbon monoxide with high faradaic efficiency on mercury free electrodes using M(cyclam) complexes.

Atrazine is a pesticide used to control broadleaf weeds, however its wide distribution and its high persistence in the soil and in surface waters has resulted in a public and environmental health problem. Present results shows the design, construction and characterization of glassy carbon electrodes modified with tetrarutenated metalloporphyrin (M=Ni (II) and Zn (II)) and 1‐butyl‐3‐methylimidazolium bis (trifluoromethylsulfonyl) imide, BMIMNTF2. The modification was reproducible and sensitive for the electrochemical detection of atrazine in neutral media. The detection limit was 230 nM when using GC/BMIMNTF2/ZnTRP and 540 nM with GC/BMIMNTF2/NiTRP, meaning that his methodology can be a feasible and inexpensive way to detect atrazine in trace levels.

The electrochemical reduction of carbon dioxide is studied herein by using conducting polymers based on metallotetraruthenated porphyrins (MTRPs). The polymers on glassy carbon electrodes were obtained by electropolymerization processes of the monomeric MTRP. The linear sweep voltammetry technique resulted in polymeric films that showed electrocatalytic activity toward carbon dioxide reduction with an onset potential of -0.70 V. The reduction products obtained were hydrogen, formic acid, formaldehyde, and methanol, with a tendency for a high production of methanol with a maximum value of turnover frequency equal to 15.07 when using a zinc(II) polymeric surface. Studies of the morphology (AFM) and electrochemical impedance spectroscopy results provide an adequate background to explain that the electrochemical reduction is governed by the roughness of the polymer, for which the possible mechanism involves a series of one-electron reduction reactions.

Glassy carbon electrodes modified with conducting polymers of Ni(II), Zn(II) and metal free tetraruthenated porphyrin were evaluated for reduction and oxidation processes of S(IV) oxoanions in Na2SO3/water‐ethanol at pH 1.0 and 3.5, showing electrocatalytic activity. A Ni(II) film was able to reduce the S(IV) oxoanions selectively in presence of high concentration of gallic acid. The Ni(II) film was also used as an amperometric sensor toward S(IV) oxoanions reduction in white wine samples showing a detection and quantification limit of 1.40 mg L−1 and 4.68 mg L−1, respectively. These results are promising for the electrochemical determination of S(IV) using conducting polymers from these macrocycles.

This work describes the electrochemical reduction of carbon dioxide in aqueous solution mediated by tetraruthenated metalloporphyrins (TRP; Co(II) and Zn(II)) in Nafion (Nf) and polyvinyl chloride (PVC) as a support. The comparative aspects of the two polymeric matrices are expressed in terms of the electrocatalytic behavior toward carbon dioxide reduction of both sets of modified electrodes; values of overpotential and turnover frequency were calculated in each case. The modified electrodes under survey were able to reduce carbon dioxide at −600 mV vs Ag/AgCl showing an enhanced reduction current and a decrease in the required overpotential compared to a bare glassy carbon (GC) electrode. Potential‐controlled electrolysis experiments were carried out at −1000 mV in order to compare the distribution of products. The production of formic acid, formaldehyde and methanol was confirmed at potentials where reduction of solvent may occur. Measurements of electrochemical impedance spectroscopy show the presence of one active site for GC/Nf/MTRP (where M=Zn(II) and Co(II)) and three for GC/PVC/MTRP. This information corroborates the high values of TOF obtained for GC/PVC/ZnTRP as the best electrocatalyst.

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.