Search results for "electroquímica"
showing 10 items of 75 documents
Influence of the Heating Rate on the Annealing Treatment of Iron Oxide Nanostructures Obtained by Electrochemical Anodization under Hydrodynamic Cond…
2017
[EN] Iron oxide nanostructures are promising materials for photoelectrochemical applications such as water splitting. In this work, electrochemical anodization of iron is used to form different iron oxide nanostructures, and the influence of different anodization parameters was studied in order to find the most suitable nanostructure for photocatalysis applications. On the one hand, hydrodynamic conditions were evaluated by stirring the electrode at different rotation speeds during the electrochemical anodization to check their influence on the formation of the nanostructures. On the other hand, different heating rates during the annealing treatment were studied for obtaining efficient iron…
Photoelectrocatalyzed degradation of a pesticides mixture solution (chlorfenvinphos and bromacil) by WO3 nanosheets
2019
[EN] A photoelectrocatalyst consisting of WO3 nanosheets or nanorods has been synthesized by electrochemical anodization under hydrodynamic conditions, and has been used for the degradation of two toxic pesticides: chlorfenvinphos and bromacil. Nanostructures have been characterized by FESEM and Raman spectroscopy. Photoelectrochemical degradation tests have been carried out both for individual pesticide solutions and for a mixture solution, and the concentration evolution with time has been followed by UV¿Vis spectrophotometry. For individual pesticides, pseudo-first order kinetic coefficients of 0.402 h¿1 and 0.324 h¿1 have been obtained for chlorfenvinphos and bromacil, respectively, whi…
Visible-light photoelectrodegradation of diuron on WO3 nanostructures
2018
[EN] The degradation of pesticide diuron has been explored by photoelectrocatalysis (PEC) under visible light illumination using two different WO3 nanostructures, obtained by anodization of tungsten. The highest degradation efficiency (73%) was obtained for WO3 nanosheets synthesized in the presence of small amounts of hydrogen peroxide (0.05 M). For that nanostructure, the kinetic coefficient for diuron degradation was 133% higher than that for the other nanostructure (anodized in the presence of fluoride anions). These results have been explained by taking into account the different architecture and dimensions of the two WO3 nanostructures under study.
Synthesis of polymer nanogels by electro-Fenton process: investigation of the effect of main operation parameters
2017
Recently, electro-Fenton (EF) process has been shown as a promising, facile, effective, low cost and environmentally-friendly alternative for synthesizing polymer nanogels suitable as biocompatible nanocarriers for emerging biomedical applications. Here, the electrochemically-assisted modification of poly(vinylpyrrolidone) (PVP) by EF process was studied to assess the role of key operation parameters for a precise modulation of polymer crosslinking and its functionalization with [sbnd]COOH and succinimide groups. The dimensions of the nanogels, in terms of hydrodynamic radius (Rh) and weight-average molecular weight (Mw), can be tuned up by controlling the electrolysis time, current density…
Facile crosslinking of poly(vinylpyrrolidone) by electro-oxidation with IrO2-based anode under potentiostatic conditions
2018
Abstract: The modification of polymer architectures by reaction with chemically adsorbed hydroxyl radicals has been thoroughly investigated by electrolyzing dilute aqueous solutions of the biocompatible polymer poly(vinylpyrrolidone) (PVP), using an undivided electrolytic cell with a Ti/IrO2–Ta2O5(DSA®) anode. Several electrolyses were performed to assess the influence of the applied potential, the circulated charge and the PVP concentration, which was always kept low to avoid chain overlapping. From the results obtained, it can be concluded that the electro-oxidation of PVP solutions using a cheap anode is an effective method to crosslink initially isolated polymer chains, eventually incre…
Photoelectrochemical removal of chlorfenvinphos by using WO3 nanorods: Influence of annealing temperature and operation pH
2019
[EN] A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400¿°C and 600¿°C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenv…
Corrosion behaviour of a highly alloyed austenitic alloy UB6 in contaminated phosphoric acid
2013
The influence of temperature (20–80°C) on the electrochemical behaviour of passive films anodically formed on UB6 stainless steel in phosphoric acid solution (5.5 M H3PO4) has been examined by using potentiodynamic curves, electrochemical impedance spectroscopy, and Mott-Schottky analysis. UB6 stainless steel in contaminated phosphoric acid is characterised by high interfacial impedance, thereby, illustrating its high corrosion resistance. The obtained results show that the films behave as n-type and p-type semiconductors in the potential range above and below the flat band potential, respectively. This behaviour is assumed to be the consequence of the semiconducting properties of the iron …
Effect of alloying elements on the electronic properties of thin passive films formed on carbon steel, ferritic and austenitic stainless steels in a …
2014
The influence of alloying elements on the electrochemical and semiconducting properties of thin passive films formed on several steels (carbon steel, ferritic and austenitic stainless steels) has been studied in a highly concentrated lithium bromide (LiBr) solution at 25 °C, by means of potentiodynamic tests and Mott Schottky analysis. The addition of Cr to carbon steel promoted the formation of a p-type semiconducting region in the passive film. A high Ni contentmodified the electronic behaviour of highly alloyed austenitic stainless steels.Mo did notmodify the electronic structure of the passive films, but reduced the concentration of defects.
Cathodoluminescence characterization of ZnO/ZnS nanostructures anodized under hydrodynamic conditions
2018
[EN] ZnO/ZnS nanostructures were successfully synthesized by a simple electrochemical anodization of zinc in a glycerol based electrolyte containing sulfide-ammonium fluoride. The influence of different hydrodynamic conditions and anodization potentials during anodization on the morphological and electronic properties of the obtained ZnO/ZnS nanostructures was studied. The anodized samples were characterized using confocal Raman microscopy, X-Ray Diffraction (XRD), Field Emission Scanning Electronic Microscopy (FE-SEM), cathodoluminescence (CL), and photoelectrochemical water splitting tests under standard AM 1.5 conditions. The results showed that hydrodynamic conditions and higher potenti…
Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr(III) passivation baths
2014
[EN] Conversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and e…