Luk'yanenko T. Electrodeposition of PbO2-based composite electrocatalysts from methanesulfonate electrolytes

The subject of investigation - electrocatalytic processes which proceed on electrodes at high anode potentials with the participation of oxygen-containing particles. Purpose of investigation - establishment of the general regularities of a nucleation and electrodeposition of dioxide of lead from the methanesulfonate of solutions, and also influences of components of electrolytes and parameters of electrolysis on texture, a phase and chemical composition of the received materials, their physical and chemical properties and electrocatalytic activity. Methods of investigation - stationary and cyclic voltamperometria, hronoamperometria, method of an electrode impedance, method of the rotating disk electrode; photocolorimetry, fluorescent and a spektrofotomeria in UF and seen areas, nuclear and absorbing spectroscopy, a highly effective liquid chromatography; scanning electronic and nuclear and power microscopy, x-ray diffraction, the x-ray microanalysis, a statistical method. Theoretical and practical results: It has been found that lead dioxide nucleation accelerates in the presence of methanesulfonate ions in the deposition electrolyte. Unlike nitrate bath, а-phase of PbO2 in the methanesulfonate solution is the predominant allotropic modification. An identified extreme dependence of the oxide deposition rate on the concentration of methanesulfonate ions in the solution is caused by the formation of lead methanesulfonate complexes and their adsorption on the electrode. The presence of ionic additives in the solution leads to inhibition of PbO2 electrodeposition due to adsorption of those ions on the surface of growing deposit. Additives are considered to be included into growing lead dioxide by ion exchange mechanism. As a result, dopants affect both phase composition of the coating and hydroxylation degree of the oxide surface layer as well as electrocatalytic activity of the obtained materials. An extreme dependence of the electrodeposition rate of lead dioxide on the content of dispersed phase particles, which does not have their own electrochemical activity, has been identified. Proposed extended kinetic scheme takes into account both complexa-tion and formation of electroactive particles that include parts of colloidal valve metal oxides. Revealed extreme dependence of the oxygen evolution reaction overvoltage on the content of methanesulfonate ions in the deposition electrolyte is caused by the change in phase composition and degree of crystallinity of PbO2. Scope of use: The complex of systematic experimental data which have been presented in dissertation work about influence of various factors on crystallization, the phase and chemical composition, and also a number of physical and chemical properties of the materials on the basis of dioxide of lead received from the methanesulfonate of electrolytes is a scientific basis of the latest ecologically safe technologies of electrochemical synthesis of oxides coverings on the basis of PbO2 of the set structure and their use in processes of destruction of toxic organic compounds (electrochemical power, electroplating, synthesis of strong oxidizers, etc.).