Fabrication, design and investigation of functional properties of composite materials based on titanium suboxides with low noble metal content for use in electrocatalysis has been investigated. The study particularly focuses on electrode coatings derived from titanium dioxide modified with platinum and palladium. The structural, electrocatalytic, and corrosion-resistant properties of these materials were systematically investigated. It was demonstrated that thermal treatment significantly enhances the catalytic efficiency of the coatings by reducing the oxygen evolution overpotential and improving the efficiency of hypochlorite synthesis. Optimal thermal treatment conditions (500 degrees C, 3 hours) were identified, resulting in increased stability of the anodes containing Pt and Pd layers, as evidenced by a service life of 176 hours. The study highlights the potential of these composites for applications in oxygen evolution reactions and hypochlorite synthesis, owing to their high stability, selectivity, and cost-effectiveness.

This study reports a combined electrochemical method for preparation of a titanium dioxide–suboxide composite with an electrochemically deposited non-continuous platinum layer on the surface, which can be used for cathodic protection of metal structures. Platinum significantly modifies the properties of TiO2, stabilizes the surface, and prevents the formation of a passive non-conductive layer. The coating has significant advantages compared to Ti/Pt, traditionally used for electrochemical protection, as the platinum content in the composite is significantly reduced. Unlike a continuous precious metal layer, this method of composite formation, particularly thermal treatment in an air atmosphere at 5000C, allows protecting the platinum, which is encapsulated in titanium oxides, and avoiding the creeping passivation typical of traditionally used materials. The surface of the coatings was investigated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and X-ray microanalysis. Studies of the electrocatalytic properties, especially concerning the oxygen evolution reaction, revealed deviations of the Tafel slope from the theoretical value, which is explained by structural heterogeneity and the presence of a semiconductor component. The stability and corrosion resistance of the composites were studied. It was found that the properties remain unchanged even after prolonged exposure to a corrosive environment.

The influence of the synthesis conditions on the surface morphology, phase composition, and electrocatalytic activity of materials in oxygen and hydrogen evolution reactions was investigated. For instance, the slopes in the potential verses the logarithm of the current density dependencies during oxygen evolution were 221 and 109 mV/dec for TiO2 nanotubes and platinum-coated layers, respectively. In the latter case, small deviations may be attributed to the structural heterogeneity of the material or the developed surface of the coating. As for pristine TiO2 nanotubes, an atypical Tafel slope was observed, almost twice the theoretical value, indicating the presence of a semiconductor component in the electrode capacitance. Studies showed that the materials are n-type semiconductors. The cathodic polarization stage leads to the formation of titanium suboxides in the nanotube recovery phase, contributing to an increase in the material electrical conductivity. This also allows for the creation of a porous developed surface matrix for the electrodeposition of catalytic metal layers. Tafel slopes were calculated for the investigated materials in the hydrogen evolution reaction. For TiO2 nanotubes, a slope of 175 mV/dec was observed. The material surface was partially blocked by hydroxides, resulting in a low number of active centers for the hydrogen evolution, and the polarization curve had a steep slope. In the case of TiO2 nanotubes coated with a platinum layer, a high number of cationic vacancies in the matrix and a deficit of oxygen ions facilitated the mobility of platinum atoms, leading to the emergence of a large number of active centers for the hydrogen evolution. As a result, the Tafel slope of the polarization curve was found to be 30 mV/dec.

This study focuses on the surface structures and microstructural changes of titanium dioxide nanotubes, when electrochemically coated with platinum and/or palladium. Ti samples anodized in a fluorine-containing electrolyte exhibit self-organized nanotubes of varying diameters with open pores. Annealing at 773 K led to compaction of the porous layer, the formation of cracks, and the appearance of corrugation in the nanotubes. The deposition of platinum produced a transition from a nanotubular surface structure to a microcrystalline structure consisting of rutile crystallites. The palladium-coated samples showed fused blocks characteristic of titanium suboxides. The tubular structure was preserved, even after crystallization. SEM images revealed a comb-like pattern in coatings with varying metal content. XRPD analysis confirmed the presence of anatase and elemental titanium. PdO was detected on the surface of the thermally treated samples. For samples co-treated with Pd and Pt, mutual diffusion of the two metals took place during the heat treatment. The findings reveal surface characteristics, metal deposition effects, and phase composition of titania nanotubes, providing valuable insights for further research.

BACKGROUND: The synthesis of sodium hypochlorite solutions by electrolysis of low-concentration and isotonic NaCl solutions using the most available dimensionally stable anodes from platinized titanium is promising from the point of view of the economics of the process. However, such synthesis is seriously complicated by the formation of toxic sodium chlorate impurity.RESULTS: It is shown that in low-concentration NaCl solutions under anodic polarization, the platinum surface rapidly passes into an oxidized passive state with a NaClO current efficiency (CE) of less than 30% and CE of NaClO3 of more than 20%. Carrying out short-term electrolysis on the reduced surface of platinum makes it possible to increase the CE of NaClO to almost 90% in the absence of chlorate accumulation. Carrying out electrolysis in the mode of periodic change of electrode polarity (current reverse) allows solving the problem of anode passivation and significantly increasing the purity of the resulting sodium hypochlorite solutions.CONCLUSION: Electrolysis of an isotonic 0.15 mol L-1 NaCl solution in the current reverse mode allows increasing CE(NaClO) from 21% to 40% and significantly decreasing CE(NaClO3) from 21% to 4%. Based on the results obtained, a membraneless electrolyzer can be constructed to produce disinfectant solutions 'on the spot' using a commercially available pharmaceutical isotonic solution of NaCl.(c) 2023 Society of Chemical Industry (SCI).

BACKGROUND: The synthesis of sodium hypochlorite (NaClO) by classical electrolysis of NaCl solutions on a Ti/Pt anode is characterized by parallel formation of undesirable sodium chlorate (NaClO3) impurities. Oxidation of hypochlorite to chlorate with high current efficiency (CE) is realized on the oxidized, passivated Pt surface. On a Pt surface reduced by cathodic polarization, NaClO synthesis can be realized with the CE close to 90% almost without chlorate accumulation. Long-term electrolysis leads to passivation of the Pt surface. RESULTS: Electrolysis while periodically changing the polarity of the electrodes (current reverse mode) increases the time the Pt surface remains in the activated state. Carrying out electrolysis in this way makes it possible to increase CE(NaClO) 1.5-2.0-fold while simultaneously reducing CE(NaClO3) (sodium chlorate) by <= 10-fold. This study additionally determined the optimal parameters of reverse electrolysis, examined the effect of changing polarity on the state of the Ti/Pt electrode surface and studied the kinetic patterns of active platinum coating dissolution. CONCLUSION: The optimal conditions for electrolysis in current reverse mode are current densities of 5-10 mA cm(-2) with the period of polarity change close to 30 s. The result of such a process is an isotonic solution containing 500 mg L-1 NaClO with an admixture of <10 mg L-1 NaClO3 and 0.1 mg L-1 Pt in the form of soluble chloride complexes. The rate of Pt accumulation is determined by the frequency of polarity change. The resulting solutions have sufficiently high purity for use in medicine and aerosol air disinfection. (c) 2024 Society of Chemical Industry (SCI).

This study focuses on titanium dioxide (TiO2) nanotubes on solid substrates, which may find wide applications as photocatalysts and catalysts. To address the need for more stable and active electrocatalysts with reduced noble metal content, the study explores TinO2n–1 suboxides as promising substrates for the electrocatalysts. Notably, the addition of water in the fluoride-containing electrolyte plays a critical role in shaping the morphology of TiO2 nanotubes, leading to the formation of ordered structures under specific water concentration conditions. The study also examines the effects of platinum and palladium deposition on TiO2 nanotubes, enhancing their surface crystallinity and structural arrangement. The presence of an unidentified phase, possibly titanium hydride, is observed in certain samples. The findings highlight the potential of TiO2 nanotubes as efficient electrocatalysts and the influence of water content and substrate choice on their properties, opening up new avenues for advanced applications in various fields.

This work reports the optimal conditions for the synthesis of a matrix for the creation of photo- and electrocatalysts. Specifically, it is shown that TiO2 nanotube arrays has a high specific surface area and improved catalytic properties, but has low conductivity and weak structural strength, that requires further optimization. The original TiO2 nanotubes were prepared by anodizing of Ti foil in ethylene glycol with 0.3 wt.% ammonium fluoride and 2 vol.% water at a constant potential, followed by another anodizing in ethylene glycol with 5 wt.%H3PO4. The reduction was conducted in 1 M HClO4. Some samples were thermally treated in the air using tube furnace. The study demonstrates how the synthesis conditions of the coating affect the morphology and stoichiometry of the resulting oxide coating. For the obtained materials, the Tafel slope in the oxygen evolution reaction is determined by the semiconductor characteristics of the coating, which, in turn, depend on the stoichiometry of the synthesized oxide. The higher the stoichiometry in the oxygen sublattice, the fewer the charge carriers and the greater the contribution of the semiconductor component to the Tafel slope. As for hydrogen evolution, the layers obtained after heat treatment show a lower Tafel slope (175 mV dec–1).

Electrodes made of platinized titanium with a surface platinum content of 2–3 mg/cm2 can be used in non-diaphragm flow- and accumulative-type electrolyzers for the electrolysis of low-concentrated NaCl solutions in order to obtain pure NaClO solutions. If electrolysis of 0.15 M NaCl solution is carried out on platinized titanium electrodes in the usual mode at current densities of 20–40 mA/cm2, then the anode surface passes into an oxidized passive state. In this case, the current efficiency of hypochlorite does not exceed 40%, and the current efficiency of chlorate is more than 20%. During a short electrolysis on a preliminarily reduced surface of platinized titanium, the current efficiency of hypochlorite reaches 90% with almost no accumulation of chlorate. Carrying out the long-term electrolysis of low-concentrated NaCl solutions in the regime of periodic polarity reverse makes it possible to significantly (up to 10 times) reduce the content of chlorate in the resulting sodium hypochlorite solutions. The most promising is the synthesis of sodium hypochlorite solutions in flow-type electrochemical reactors consisting of several series-connected electrochemical modules with an undivided electrode space in the mode of periodic current reverse. The electrolyzer of two series-connected cells in the mode without current reverse allows obtaining a solution that contains 500 mg/L of sodium hypochlorite and 130 mg/L of sodium chlorate. Carrying out the electrolysis in the reverse current mode every 30 s reduces the content of sodium chlorate to 25 mg/L, which makes it possible to produce high-purity NaClO solutions.

An original approach to the creation of new nanocomposite anode materials based on PbO2 and to the processes of composite formation due to the influence of selective adsorption of valve metal oxides and different types of surfactants on both electrochemical and colloid-chemical processes in the near-electrode zone is considered. It is shown that variation of deposition electrolyte composition, current density, and temperature allows one to change the content of additives in composites and to provide control of morphology, texture, phase composition, physicochemical properties, electrocatalytic activity, and selectivity of electrocatalysts based on PbO2 in target processes.

In the review article, a critical analysis of the literature was carried out, which showed the almost complete absence of systematic studies of electrochemical processes implemented at anodes in low-concentrationed sodium chloride solutions. The vast majority of works are devoted to the study of the regularities of chlorine evolution reaction in highly concentrated NaCl solutions on the surface of oxide catalysts, which often contain oxides of ruthenium and iridium. Taking into account the variety of works, today there is no universal mechanism that describes the reaction of chlorine evolution under various conditions and on the surfaces of electrocatalysts of various nature. Comprehensive data on the peculiarities of such processes in low concentrated chloride solutions are presented. It is shown that the regularities of such processes are due to the participation of oxygen-containing particles with different bond strengths in individual steps. It was found that the electrocatalytic activity of electrodes in anodic processes in low concentrationed-chloride solutions was due to the strength of the bond of chemisorbed oxygen-containing particles of different nature with the anode surface. Participation in the oxidation of Cl(- )labile oxygen-containing particles of a certain energy increases the rate of formation of hypochlorous acid and leads to inhibition of undesirable reactions of oxygen evolution and synthesis of chlorates and chlorites. It is shown that the modification of the anode surface with palladium makes it possible to significantly increase their selectivity for the synthesis of hypochlorous acid from low concentration chloride solutions.

The regularities of electrosynthesis, properties, and electrocatalytic activity of the composites lead dioxideperfluorooctanesulfonate have been investigated. Comprehensive data on the regularities of PbO2 nucleation in the presence of perfluorooctane sulfonate in the deposition electrolyte are obtained. The kinetics of the deposition of composites in the presence of surfactant in the deposition electrolyte has been studied, it is shown that the effect of inhibiting of PbO2 deposition, which is evident more with increasing of fluorine-carbon chain length, no longer evident when the chain reaches eight carbon atoms. The morphology and phase composition of composites were studied. The influence of the composition of composites on the reaction of oxygen evolution and oxidation of 4-chlorophenol was studied.

BACKGROUND Creation of anode materials with high selectivity to the target process is the main problem in low concentration sodium chloride (NaCl) solutions. A specificity of such solutions is the achievement of high potentials at which the anodes traditionally used for the synthesis of chlorine [rutile oxide/titania (RuO2-TiO2)] are destroyed. The main aim of the work concerns the eveluation of the effect of platinum (Pt) group metals in a tin oxide (SnO2) matrix on the electrocatalytic activity and selectivity in reactions of the synthesis of sodium hypochlorite and chlorate (NaClO and NaClO3) and oxygen (O-2) evolution. RESULTS It was revealed that palladium (Pd) in oxide Ti/SnO2-Pd and Ti/SnO2-Pt-Pd coatings existed in the PdO form, which has a high affinity for hydroxylation. Electrocatalytic activity of coatings in anode processes in low concentrated chloride-containing solutions would be determined by the bond strength of chemisorbed with the surface O-containing particles. Participation in the process of Cl- oxidation of labile O-containing particles increased the rate of formation of NaClO and led to inhibition of adverse reactions of O-2 evolution and synthesis of chlorates and chlorites. CONCLUSION A correlation between the selectivity of formation of NaClO and NaClO3, and the activity of the catalyst in the O-2 evolution reaction is proposed. Significant formation of chlorates occurred only at the anodes, where in 1 mol L-1 HClO4 the O-2 evolution potential was >1.58 V. Parameters influencing the electrocatalytic activity and selectivity of electrode materials in the target process were proposed based on this dependence. (c) 2021 Society of Chemical Industry (SCI).

Titanium dioxide is one of the main products of chemical industry. Due to its optical properties, it is most widely used in the paint and varnish industry and the production of pigments. Its sensory, adsorption, optical, electrical, and catalytic properties are widely recognized as the objects of close attention of researchers [1]. Due to its high chemical inertness, lack of toxicity and low cost, titanium dioxide is increasingly used as a photocatalyst, while it has a number of significant disadvantages: low quantum efficiency of the process due to weak separation of the electron-hole pair, limited absorption spectrum in the ultraviolet region, which makes it impossible to use the energy of sunlight [2,3]. Scientists in all leading countries of the world are engaged in solving these problems. It is known that nanosized TiO2 particles (<50 nm) have the highest photocatalytic activity; therefore, the preparation of TiO2 nanoparticles is one of the ways to reduce the degree of charge recombination and increase the active surface area of the oxide [4]. We propose to use a combined electrochemical-pyrolytic method of nanotube synthesis. This method will allow one to create a porous developed surface of the matrix for electrodeposition of catalytic layers of platinum and palladium; and their subsequent heat treatment at different partial pressures of oxygen will allow one to design composites with different composition. The high number of cationic vacancies in the matrix and the deficiency of oxygen ions will significantly increase the mobility of platinum and palladium atoms during heat treatment, and the resulting composite will have practically metal conductivity, high catalytic activity, selectivity and extended service life. Naked Ti/TiO2 contain a significant amount of X-ray amorphous compounds on the surface, which are most likely hydrated titanium oxides. The main crystalline phase is titanium dioxide in the allotropic anatase form. Metallic titanium is present on the surface in trace amounts. Thermal treatment of this material at a temperature of 500 ºC for 3 hours in an air atmosphere leads to an increase in the proportion of the crystalline phase. The content of metallic titanium increases significantly, reaching about a third. A partial electrochemical reduction of nanotubes allows one to obtain more electrically conductive titanium suboxides. After cathodic reduction of nanotubes for one hour, a galvanic coating with metallic platinum is uniformly deposited on the surface of the material. Thermal treated Ti/TiO2 nanotubes is an n-type semiconductor with a flat-band potential equal to –0.589 V and a carrier concentration of 6×1020 cm-3. Such a high concentration of carriers is obviously due to the small thickness of the oxide film and its nonstoichiometry, as a result of which the surface is not very depleted in electrons, since titanium metal acts as their donor. An original technique was developed for the deposition of platinized Ti/TiO2 nanotubes, including the stage of thermal treatment of the coating in an air atmosphere. It has been shown that the deposition of platinum on the previously reduced surface of nanotubes allows one to obtain composite coatings with a higher electrical conductivity, and the heat treatment of such a coating is characterized by the content of a larger fraction of TiO2, increased adhesion to the current collector, and an increase in the crystallinity of the coating. At the same time, the internal stresses of the coating are reduced by several times. References V.R.A. Ferreira, P.R.M. Santos, C.I.Q. Silva, M.A. Azenha. Latest developments on TiO2-based photocatalysis: a special focus on selectivity and hollownes for enhanced photonic efficiency, Appl. Catal., A, 623, 118243 (2021). S. Palmas, L. Mais, M. Mascia, A. Vacca. Trend in using TiO2nanotubes as photoelectrodes in PEC processes for wastewater treatment, Curr. Opin. Electrochem., 28, 100699 (2021). E. Brillas. A critical review on ibuprofen removal from synthetic waters, natural waters, and real wastewaters by advanced oxidation processes, Chemosphere, 286, 131849 (2022). M. Bellardita, A. Di Paola, L. Palmisano, F. Parrini, G. Buscarino, R. Amadelli, Preparation and photoactivity of samarium loaded anatase, brookite and rutile catalysts, Appl. Catal., B, 104, 291-299 (2011).

Anode processes on SnO2-based electrodes in low-concentrated NaCl solutions have been investigated. The current-voltage curves for 25 tin oxide anodes doped with various amounts of platinum group metals in 0.5 M NaClO4 and 0.5 M NaClO4 + 0.5 M NaCl have been analyzed. The correlation criterion between the catalytic activity of the coating in relation to the reaction of synthesis of NaClO, NaClO3 from low-concentrated NaCl solutions, and the oxygen evolution overpotential was found. The formulated criterion is fully met by SnO2-coatings doped with both palladium (5-15 at.%) and platinum (5-10 at.%), which are the optimal electrocatalysts for the synthesis of sodium hypochlorite. In this case, their catalytic activity does not depend on the concentrations of dopant in the range, which allows to obtain anodes with reproducible properties by pyrolysis. The current efficiency of NaClO is 90-95% and current efficiency of chlorate is less than 1% during the electrolysis of 0.15 M NaCl on Ti/SnO2-Pt-Pd anodes at 40-60 mA/cm(2). Palladium exists in the form of PdO phase in the electrocatalytic coating Ti/SnO2-Pt-Pd. The surface oxygen concentration in H2Oads and OHads is comparable to the oxygen content of the phase oxides of tin and palladium in the coating containing 19.5 at.% Pd, indicating a high surface content of adsorbed water. Palladium oxides are the main centers of water adsorption, and their presence on the surface of the anodes contributes to the hydroxylation of the surface. Most likely, this property of palladium compounds provides its high electrocatalytic activity in the reaction of formation of hypochlorite, which involves labile oxygen-containing particles low bonded to the surface.

Electrochemical synthesis allows one to influence the composition and properties of materials by changing the conditions of electrolysis and electrolyte composition. Lead dioxide due to the simplicity of its electrochemical synthesis, high corrosion resistance and relatively low cost is widely used in electrocatalysis, electroplating, lead-acid batteries, etc. The inclusion of fluorine-containing compounds in the metal oxide matrix provides antistatic, anti-adhesive, anti-corrosion properties, and at the same time the materials retain the properties of metal oxide: high electrical conductivity, resistance to mechanical wear and good adhesion to the substrate. In this work, the regularities of lead dioxide electrosynthesis in the presence of fluorine-containing surfactants with different fluor-carbon chain lengths and polyelectrolytes in the electrolyte were investigated. Electrodeposition was studied in 0.11 M CH 3 SO 3 H + 0.01 M Pb (CH 3 SO 3 ) 2 . The surfactant was added to the deposition electrolyte in the form of aqueous solutions with a concentration of 3×10 -4 M. Determination of current efficiency and partial oxidation current (I Pb(II) ) was performed by the method described in detail previously [1]. The kinetic regularities of PbO 2 electrodeposition are satisfactorily described in a four-stage mechanism applied to a wide range of electrolytes (both nitrate and methanesulfonate), including those containing ionic additives, colloidal TiO 2 and polyelectrolytes [2,3]. As a rule, at low anodic polarizations (E <1.6 V) the reactions will take place with kinetic control, while at high polarizations the delivery of Pb 2+ ions to the electrode surface will be the rate-determining stage. It was found that the addition of surfactants and polyelectrolytes in different ways affect the kinetics of electrodeposition of lead dioxide, without changing the mechanism of the process. The basis of the surface effects is the adsorption of additives on the electrode surface. The adsorption on the electrode of methanesulfonate and fluoride ions significantly affects the rate of the discharge-ionization stage. This effect is due to a number of factors that lead to changes in the concentration of reacting particles in the surface layer and the activation energy of the electrode process. Since the value of surface charge is positive, a decrease in the value of the potential in the plane of localization of the activated complex will increase the rate of the charge transfer stage, which is observed in practice in solutions containing short-chain perfluoroalkyl surfactants and low concentrations of Nafion ® polymer. During the adsorption of a polyelectrolyte or anionic surfactant on the surface of the electrode, the value of such potential can not only decrease significantly, but even become negative due to recharging of the electric double layer. This possibility is indicated by the change in the electrokinetic potential of PbO 2 from positive to negative by adding anionic surfactants and polymers to the electrolyte. The inhibition parameter reflects both the electrostatic and chemical interaction of the activated complex with the adsorption layer, which leads to an increase in the activation energy of the charge transfer stage. Increasing the volume concentration of the additive in the electrolyte leads to an increase in the degree of filling of the electrode surface, which will cause a decrease in the rate of the charge transfer stage due to blocking of active centers on the electrode surface. Since the process of formation of lead dioxide takes place together with the reaction of oxygen evolution, the dependences of PbO 2 current efficiencies (CE) on the electrodeposition potential were investigated to assess the influence of surfactants on the lead dioxide electrodeposition. In the low polarizations area, the PbO 2 CE remains virtually unchanged, close to 100%. In this area, the deposition process is controlled by kinetic stages. If the additive does not inhibit the deposition of lead oxide, CE is close to 100% and is almost independent of the current density. In the next part of the curve the process of electrodeposition of oxide occurs under mixed control. On the descending part of the dependence CE decreases due to the increase in the reaction rate of oxygen evolution when the limiting current of electrodeposition of oxide is observed (diffusion control). References A. Velichenko, T. Luk’yanenko, O. Shmychkova, L. Dmitrikova, Electrosynthesis and catalytic activity of PbO 2 -fluorinated surfactant composites, J. Chem. Technol. Biotechnol., 95 , 3085, (2020). A. Velichenko, T. Luk’yanenko, N. Nikolenko, O. Shmychkova, P. Demchenko, R. Gladyshevskii, Composite electrodes PbO 2 -Nafion ® , J. Electrochem. Soc., 167 , 063501 (2020). O. Shmychkova, T. Luk’yanenko, A. Velichenko, Lead dioxide electrocrystallization from nitrate and methanesulfonate electrolytes: The influence of various dopants on initial stages, ECS Transactions, 77, 1617 (2017).

Naked Ti/TiO2 contains a significant amount of X-ray amorphous compounds on the surface, which are most likely hydrated titanium oxides. The main crystalline phase is titanium dioxide in the allotropic anatase form. Metallic titanium is present on the surface in trace amounts. Thermal treatment of this material at a temperature of 5000C for 3 hours in an air atmosphere leads to an increase in the proportion of the crystalline phase. The content of metallic titanium increases significantly, reaching about a third. A partial electrochemical reduction of nanotubes allows one to obtain more electrically conductive titanium suboxides. After cathodic reduction of nanotubes for one hour, a coating with metallic platinum is uniformly deposited on the surface of the material. Thermal treated Ti/TiO2 nanotubes are an n-type semiconductor with a flat-band potential equal to –0.589 V and a carrier concentration of 61020 cm–3. Such a high concentration of carriers is obviously due to the small thickness of the oxide film and its nonstoichiometry, as a result of which the surface is not very depleted in electrons, since titanium metal acts as their donor.

The main requirements for anode materials can be divided into two groups: i) overall operating (satisfactory electrical conductivity, availability and reasonable cost, long service life, etc.); ii) specific, due to particular target process (high electrocatalytic activity and selectivity) [1]. The lack of universal anode material requires the creation of new approaches to managing the functional properties of the catalyst. In our opinion, the optimal strategy is to choose a base material that meets the general operational requirements, followed by the creation of an active layer on its basis in accordance with the requirements of particular target processes. The regularities of formation of composites of the TiOx-Pt and TiOx-Pt-Pd systems and their physicochemical properties were studied. Composites were obtained in two stages. First, a thin non-continuous layer of Pt or successive layers of Pt-Pd was applied to the substrate by electrodeposition. Nitrite electrolyte for platinating and phosphate palladation were used. The amount of Pt and Pd on the surface ranged from 0.1 to 2.0 mg cm-2. Then the resulting material was heat treated in an air atmosphere. The surface layers of the composites were formed due to the oxidation of the substrate and the encapsulation of platinum and palladium particles into titanium oxides during this stage. The chemical composition of the bulk and surface of the electrocatalytic coatings obtained was determined by XPS, SEM and EDAX. XPS showed that Pt exists in the metallic state, while Ti is in the form of both metal and intermetallic TixPty, with low Pt content, and in oxide form in Ti(IV) compounds on the surface of non-heat treated electrode As one can see, the coating is not uniform, and the platinum content is significantly reduced from the surface to the substrate (from 92 to 67 at.%), that indicates the local nature of the coating and confirmed by SEM data. As thermal treatment contributes to a more uniform distribution of Pt on the surface, as well as its diffusion in combination with oxygen in the coating bulk, it leads to the formation of a composite of titanium-platinum oxides. The semiconductor properties of such anodes are due to the presence of TiO2, which is an n-type semiconductor. As the temperature increases, the potentials of the flat zones and the carrier concentrations increase, which may be related to the interaction of platinum (electron donor) with TiO2. The use of titanium suboxides as a substrate and increasing the processing temperature also leads to an increase in the potential of flat zones. However, this reduces the number of carriers due to the increase in the degree of stoichiometry of titanium suboxides due to oxygen uptake. The electrodes obtained at 583 K do not correspond to the general dependence. It is likely that the new Ti-O phase formed under such conditions makes an individual contribution to the semiconductor properties of such materials. Palladation of platinum titanium does not lead to a significant change in surface morphology. Platinum, according to EDAX, is fairly evenly distributed on the surface of titanium, which is not observed for palladium. Unlike platinum, the maximum amount of palladium is observed in the protruding parts of the surface, and the minimum - in the hollows, due to the uneven distribution of current on the surface of Ti/Pt during the electrodeposition of palladium. The most noticeable change in morphology occurs at a surface Pd content of 1.0 mg cm-2. The oxygen concentration increases on the surface during heat treatment of Ti/Pt-Pd, there is oxidation of Pd, the surface becomes blue. The distribution of oxygen on the surface coincides with palladium, which indicates the formation of an oxide layer. The XRD method detected the PdO phase on the surface of heat-treated samples with a surface palladium content of 0.2 to 1.0 mg cm-2. At 2θ = 33.8°, the PdO-specific reflex is manifested, the area of which increases with increasing of surface palladium content. Thus, the use of the combined electrochemical-pyrolytic method of obtaining composite anode materials allows to create materials that differ significantly in their structural parameters, composition and physicochemical properties. The main factors influencing the properties of such materials are the nature of the substrate, the amount and nature of platinum and palladium in the surface layer, the temperature and duration of heat treatment in the air. Developed anode materials are characterized by long service life. References Walsh, F.C. Modern developments in electrodes for electrochemical technology and the role of surface finishing / F.C. Walsh // Trans. Inst. Met. Finish. – 2019. – Vol. 97(1). – P. 28-42

Rate constant (k) for the lead(II) oxidation decreases from (4.06 ± 0.10) × 10−4 to (2.80 ± 0.10) × 10−4 ms−1 when 3 × 10−4 M of dopant C6F13SO3K is added to the deposition solution. The adsorption of C6F13SO3K on PbO2 is specific, which is confirmed by the shift of pH0 of the oxide to higher value. There are no visible differences when modifying lead dioxide with perfluorohexanesulfonate, the morphology of the composite is similar to the naked sample; as well as there are only slight deviations in the texture of the composites involved. It should be noted that using a long chain compound with perfluorinated hydrocarbon radical in order to achieve higher oxidation rates of organic compounds is not recommended since a perfluorinated hydrocarbon skeleton (longer than 4 carbon atoms) can block active centers taking part in water and 4-chlorophenol oxidation.