The application of zinc citrate for the synthesis of carbon materials

Zinc citrate was prepared and its thermal decomposition was investigated by methods of thermogravimetric analysis and differential scanning calorimetry. Products of the thermal decomposition were investigated by X-ray diffraction analysis. The decomposition proceeds at temperatures 50 - 420 °C in three stages and leads to the formation of nanocrystalline ZnO with the average grain size of 23 nm. Subsequently, zinc citrate was used as a precursor of ZnO hard template for preparation of carbon mesoporous materials by the solid template method. The carbon materials were obtained by pyrolysis of polymer matrix of phenol-formaldehyde resin in which zinc citrate was added. It was found that the resulting material has a specific surface area of 1051 m2/g. According to the cyclic voltamperometry data, the material has a specific capacity 40 F/g.

POLYPYRROLE COATED CELLULOSIC SUBSTRATE MODIFIED BY COPPER OXIDE AS ELECTRODE FOR NITRATE ELECTROREDUCTION

The aim of this work is to synthesize polypyrrole (PPy) films on nonconducting cellulosic substrate and modified by copper oxide particles for use in the nitrate electroreduction process. Firstly, the chemical polymerization of polypyrrole onto cellulosic substrate is conducted by using FeCl 3 as an oxidant and pyrrole as monomer. The thickness and topography of the different PPy films obtained were estimated using a profilometer apparatus. The electrochemical reactivity of the obtained electrodes was tested by voltamperometry technique and electrochemical impedance spectroscopy. Secondly, the modification of the PPy film surface by incorporation of copper oxide particles is conducted by applying a galvanostatic procedure from a CuCl 2 solution. The SEM, EDX and XRD analysis showed the presence of CuO particles in the polymer films with dimensions less than 50 nm. From cyclic voltamperometry experiments, the composite activity for the nitrate electroreduction reaction was evaluated and the peak of nitrate reduction is found to vary linearly with initial nitrate concentration.

La dissolution anodique du cuivre en présence d'ions F− dans des solutions aqueuses acides

The influence of F− ions on the anodic dissolution of copper in aqueous acidic solutions (pH 1.6–6), mainly at pH 5 with 0.1 M KF, has been studied. The nature of the changes that occur on the electrode during the oxidation has been examined by cyclic voltamperometry as well as by different techniques of surface analysis (SEM, XPS, AES). To determine the mechanism of the electrochemical oxidation of copper at pH 5, studies with rotating disk electrodes have been carried out under conditions giving rise to a general dissolution of copper. At pH 1.6–6, the copper electrode dissolves uniformly, i.e., without preferential zones on the surface, when it is submitted to a potentiodynamic polarization (10 mV s−1) at potentials above 0 VECS. At slightly acidic pH (pH 5, KF0.1 M), with a sweep of potential up to +0.5 V, the oxidation of copper begins with a generalized corrosion of the electrode and it is followed by the formation of a film of Cu2O that is not passivating; as the oxidation proceeds, the current drops and the electrode becomes passivated. One model for the anodic dissolution is presented for the results obtained at pH 5. When a uniform corrosion develops on the rotating electrode, the copper is oxidized to Cu2+ ions. When ω → 0, the rate of dissolution of the electrode is limited by the diffusion of the Cu2+ ions from the electrode to the solution, whereas when ω → ∞ the process of charge transfer is the limiting factor to the kinetics of the dissolution. [Journal translation]