Electrochemical Method for Producing a TiO2 Film with Photocatalytic Properties

The purpose of this work is to study the production process of titanium dioxide during anode polarization in sulfuric acid and hydrochloric acid solutions. The studies were carried out by recording cyclic voltammogram and by measuring the titanium oxidation current with a change in the voltage between the electrodes. It has been established that with a change in the concentration of sulfuric acid in the range of 50–250 g/l and the voltage between the electrodes in the range of 0–25 V, the magnitude of the titanium oxidation current in-creases and reaches 29.4 mA. With an increase in the concentration of hydrochloric acid from 35 to 100 g/l and a change in the voltage between the electrodes, the titanium oxidation rate increases evenly, but in the voltage range of 10–12 V, a sharp increase in the current magnitude up to 360 mA is observed. A change in the oxidation current indicates an increase in the rate of titanium dissolution. With an increase in the duration of electrolysis, the magnitude of the anode current generally decreases. In all probability, at a voltage of 14 V and higher, a breakdown of the oxide semiconductor film of titanium dioxide is observed in the hydrochloric acid solution. In this regard, a noticeable dissolution of titanium occurs and, subsequently, an oxide film is not produced, but titanium ions are produced. Visual observations have shown that titanium passes into solu-tion in the form of titanium (IV)

Laws of Dissolution of Copper Electrodes Polarized by the Alternating Current in Solution of Potassium Iodide

Electrochemical behavior of copper in solution of potassium chloride under polarization with industrial alternating current is investigated. It is shown, that at polarization of copper-titanium electrode pair by an alternating current with frequency of 50 Hz in the solution of potassium iodide the copper electrode is dissolved, forming compound of copper (I) iodide. It is also shown, that current efficiency of formation of copper (I) iodide is influenced by (i) the density of alternating current, (ii) concentration of potassium iodide and hydrochloric acid in solution. On the basis of the research the optimum conditions of obtaining of copper (I) iodide have been determined. At the optimum conditions the current efficiency of formation of copper (I) iodide was more than 100.0%. The advantages of the electrochemical method are the economical efficiency, simplicity of process, purity of the obtained product, electrolysis at room temperature, improvement of the working conditions

Electrochemical Method of Obtaining of Electric Current from Thermal Energy Using Graphite Electrodes

Here we present the possibility of using the electrochemical processes to convert solar thermal energy or geothermal energy into electricity, based on fundamental and experimental research. Laboratory setup for converting thermal energy into electrical energy is the glass electrolyzer consisting of two electrode spaces connected with electrolytic bridge. The influence of the temperature difference between the electrode formation spaces on the EMF and the short circuit current (SCC) between graphite electrodes in aqueous solutions was studied. In solution of 100 g/l of sodium hydroxide the values of the EMF, SCC and oxidation-reduction potential are 80.0 mV, 44.1 μA and 95 mV, respectively. These values are substantially higher than those of the acidic and neutral solutions. This is due to the fact that in the alkaline solution the oxidation of hydroquinone, 1,4-benzoquinone is reversible and provides good reproducible electrode potential, which depends on the pH. The coefficient of conversion of thermal energy into electrical energy is 1.14 mV/deg

DEVELOPMENT OF A COMPOSITE ELECTRODE OF MANGANESE DIOXIDE-GRAPHITE AND RESEARCH OF ITS ELECTROCHEMICAL PROPERTIES

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Сopper powders formation in the cathodic and anodic half-periods with industrial alternating current

For the first time, an installation was created for producing copper powders in the anodic and cathodic half-periods of industrial alternating current with a frequency of 50 Hz. This device consists of two electrolytic cells interconnected in parallel, in each electrolyzer there are two copper electrodes. Two diodes are also included in the electrochemical circuit to allow current flowing in opposite directions. The influence of electrodes current density, sulfuric acid concentration, copper ions, on current output of copper powder formation in each cell was investigated. It was established that the current output increases within the current density from 2000-8000 A/m2 and decreases with further increase of this parameter. When sulfuric acid concentration was 100 g/l and copper ions concentration was 15 g/l, the maximum current output of powder in electrolyzes was 50.1-53.3%, and the total current output exceeded 100%. Using a JSM-661 LV scanning electron microscope, the shape and size of obtained powders were investigated. On the basis of the conducted studies and captured oscillograms, the mechanism for copper powders formation in the anodic and cathodic half-cycles of alternating current was established. For the first time it was shown that the proposed installation allows to obtain copper powders in two half periods of alternating current. It was established that at the same time ultrafine metal powders with particle sizes of 1.0-1.5 microns had been formed. © National Academy of Sciences of the Republic of Kazakhstan, 2019

Recovery of “Hard-to-Recover” Selenate Ions in Sulfuric Acid Solutions during Polarization of Titanium Electrodes by Industrial Alternating Current

The article is devoted to the study of selenium (VI) reduction processes in sulfuric acid solutions when titanium electrodes are polarized by alternating current of industrial frequency (50 Hz). It was found that selenate ion reduction occurs on the surface of titanium electrodes in the cathode half-cycle of alternating current (practically at the cathode) by reaction: SeO42−+ 6e + 8H+ → Se + 4H2O. In addition, the recovery is carried out by titanium (III) ions: 6Ti3+ SeO42−+ 8H+ → Se + 6Ti4+ + 4H2O. It has been established that titanium (III) ions are products of dissolution of titanium during polarization by alternating current, so they can be formed by reaction: 2Ti + 6H+ → 2Ti3+ + 3H2. Reduction in selenate ions during polarization by alternating current can also occur due to the cementation reaction with titanium: 3Ti + 2SeO42− + 16H+ → 2Se + 8H2O + 3Ti4+. It was shown for the first time that the selenate ion is reduced to form a dispersed selenium powder with a high current efficiency. Depending on the conditions, both amorphous and crystalline selenium modifications are produced

Formation of selenium powder at reduction of seleniteions in hydrochloric acid solution on the surface of copper anode

The article shows the possibility of reduction of selenite ions in the presence of copper (II) ions with the formation of dispersed selenium powders. The effect of the concentration of hydrochloric acid, copper (II) ions, the current density at the copper anode and the solution temperature on the current efficiency (CE) of the formation of selenium powder has been studied. The current efficiency of selenium powder was calculated by the weight of the powder formed. It was found that with increase in concentration of copper (II) ions and the solution temperature, the current efficiency of the formation of elemental selenium in the form of a powder increases. It was shown that at the current density below 75 A/m2, the current efficiency of selenium powder exceeds 100%. Previous studies have shown that titanium (IV) ions cannot be used in the recovery of selenite ions. Using an electron microscope, micrographs of selenium powder were obtained. They indicate the formation of a finely dispersed selenium powder of spherical shape with an average particle size of 0.252 µm. © 2020, National Academy of Sciences of the Republic of Kazakhstan. All rights reserved