169,945 research outputs found
Electrocatalysis in anodic oxidation of organics with simultaneous oxygen evolution
No full textThe electrochemical oxidation (or combustion) of organics with simultaneous oxygen evolution was studied using different electrode materials (Ti/IrO2, Ti/SnO2). A simplified mechanism for the electrochemical oxidation of organics is presented, according to which selective oxidation occurs with oxide anodes (MOx) for which the formation of higher oxides (e.g.: MOx+1) is possible. Combustion occurs at electrodes at the surface of which OH radicals can be accumulated. Detection of OH radicals formed by water discharge at different anodes using N,N-dimethyl-p-nitrosoaniline (RNO) as a spin trap and preparative electrolysis confirmed the proposed mechanism
Electrochemical synthesis of peroxomonophosphate using boron-doped diamond anodes
No full textA new method for the synthesis of peroxomonophosphate, based on the use of boron-doped diamond electrodes, is described. The amount of oxidant electrogenerated depends on the characteristics of the supporting media (pH and solute concentration) and on the operating conditions (temperature and current density). Results show that the pH, between values of 1 and 5, does not influence either the electrosynthesis of peroxomonophosphate or the chemical stability of the oxidant generated. Conversely, low temperatures are required during the electrosynthesis process to minimize the thermal decomposition of peroxomonophosphate and to guarantee significant oxidant concentration. In addition, a marked influence of both the current density and the initial substrate is observed. This observation can be explained in terms of the contribution of hydroxyl radicals in the oxidation mechanisms that occur on diamond surfaces. In the assays carried out below the water oxidation potential, the generation of hydroxyl radicals did not take place. In these cases, peroxomonophosphate generation occurs through a direct electron transfer and, therefore, at these low current densities lower concentrations are obtained. On the other hand, at higher potentials both direct and hydroxyl radical-mediated mechanisms contribute to the oxidant generation and the process is more efficient. In the same way, the contribution of hydroxyl radicals may also help to explain the significant influence of the substrate concentration. Thus, the coexistence of both phosphate and hydroxyl radicals is required to ensure the generation of significant amounts of peroxomonophosphoric acid
Method for postharvest treating citrus fruit
No full textThe present invention relates to a method for post-harvest treating citrus fruit comprising a step of washing citrus fruit, said step of washing citrus fruit comprising: a) a step of bringing water into contact with citrus fruit; b) a step of electrolyzing said water which has been brought into contact with citrus fruit; and c) a step of using said electrolyzed water as washing water of the citrus fruit
Electrochemical behaviour of fluorinated boron-doped diamond
No full textThe surface properties and the electrochemical behavior of a fluorinated boron-doped diamond ~F-BDD! electrode prepared by plasma treatment in CF4-He mixture has been studied by X-ray photoelectron spectroscopy and cyclic voltammetry in acidic media. The results have shown the presence of carbon-fluorine bonding ~C—CF and C—F! on the surface of F-BDD, which made the surface more hydrophobic. It was also found that hydrogen evolution was shifted to more cathodic potentials for fluorinated diamond, as compared with untreated BDD. Finally, the higher cathodic overpotential for hydrogen evolution permitted nickel deposition and nitrate reduction
Controlled synthesis of Pt3Sn/C electrocatalysts with exclusive Sn-Pt interaction designed for use in direct methanol fuel cells
No full textAlloy-type Sn-Pt/C electrocatalysts with Pt/Sn= 1.8-3.0 ratios and exclusive Sn-Pt interaction have
been prepared by means of Controlled Surface Reactions (CSRs). As demonstrated by XRD the incorporation of
Sn onto Pt/C was achieved satisfactorily yielding a near-stoichiometric fcc Pt3Sn alloy phase along with a certain
amount of the Pt(1-x)Snx solid solution. The content and dispersion of the fcc Pt3Sn phase within the
electrocatalysts can be controlled by tuning the reaction conditions of CSRs. No evidence of the presence of
SnO2 phases in the Sn-modified Pt/C samples were found by means of the XRD and EDS analysis. According to
in situ XPS studies the pre-treatment in hydrogen at 350°C resulted in complete reduction of tin to Sn0. These
results demonstrate that the method of CSRs is a powerful tool to create of Pt-Sn bimetallic nanoparticles
exclusively, without tin introduction onto the carbon support. The performance of the intermetallic SnPt/C
catalysts in the CO and methanol electrooxidation reactions depends on the actual composition of the exposed
surface and the size of bimetallic particles. In the consecutive tin introduction the decrease of the amount of
SnEt4 precursor added per period, accompanied with an increase of the number of anchoring periods, resulted in
an increase of the activity in both electrooxidation reactions as a consequence of an optimal balance of Pt/Sn
ratio, the content of fcc Pt3Sn phase and metal particle size. It was demonstrated that the increasing tin content
above a certain (optimal) amount gives rise to a negative effect on the catalyst performance in the CO and
methanol electrooxidation
Oxidation of organic pollutants on BDD anodes using modulated current electrolysis
No full textIn this paper, a theoretical model is presented for organic pollutants mineralization at high current efficiency (close to 100%) and low energy consumption on boron-doped diamond electrodes. The model is formulated for a perfect mixed electrochemical reactor operated as a batch recirculation system under multiple current steps, in which the applied current is adjusted during the electrolysis to be close to the limiting value. An experimental validation with the anodic oxidation of 3,4,5-trihydroxybenzoic acid is also provided. The results have shown that multiple current steps electrolysis and continuous current control allowed obtaining high oxidation rate and current efficiency
Electrochemical oxidation of para-chlorophenol on Ti/SnO2-PbO2 electrodes: Introduction of a parameter for the estimation of their efficiency.
No full textPreparation of SnO2-Sb2O5 films by the spray pyrolysis technique
No full textSpray pyrolysis has been widely used for the preparation of thin (approximately 0.1 micron) and transparent SnO2 films on glass substrates. The parameters of the spray pyrolysis for the preparation of thick SnO2-Sb2O5 conductive films on Ti substrates were studied for electrochemical use. The resistivity of the films exhibits a minimum for a Sb concentration of approximately 3 at.% (precursor solution concentration) and for a preparation temperature of 550 °C. As far as the composition is concerned, the Sb concentration in the oxide films is about twice as large as that in the corresponding precursor solution. The dependence of the oxide loading on the substrate temperature and nature and the influence of the spray conditions also are discussed
Service life of Ti/SnO2-Sb2O5 anodes
No full textThe service life of SnO2-Sb2O5 coated anodes prepared by the spray pyrolysis technique using Ti or Ti/IrO2 substrate, was studied under galvanostatic conditions (100mA/cm2 in 1M H2SO4 at 25 °C). The results showed that the presence of an IrO2 interlayer between the Ti substrate and the SnO2-Sb2O5 coating (Ti/IrO2/SnO2-Sb2O5 anode) strongly increases the service life of the anode. This beneficial action of the IrO2 interlayer was attributed to its high anodic stability and its isomorphous structure with TiO2 and SnO2. Cyclic voltammetry and steady-state polarization curves showed that the electrochemical behaviour of the Ti/IrO2/SnO2-Sb2O5 electrode lies between the behaviour of the Ti/IrO2 and the Ti/SnO2-Sb2O5 electrodes due to incorporation of IrO2 in the SnO2-Sb2O5 coating during its preparation
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