Vladimir V. Panić

The properties of carbon-supported hydrous ruthenium oxide obtained from RuOxHy sol

Preparation of RuO x H v /carbon black nanocomposite material was performed by the impregnation method starting from RuO, H v sol as a precursor. Black Pearls 2000® (BP) and Vulcan® XC-72 R (XC) were used as supporting materials. Samples of the composite were calcined in nitrogen atmosphere at temperatures from 130 to 450 °C. Chemical and structural characterization of the precursor and the composites was performed by using energy-dispersive X-ray fluorescence spectroscopy (EDXRFS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These techniques showed that the oxide impregnated into carbon support is hydrous and amorphous. The amorphous structure is maintained if the composite is calcined up to 300 °C, while the low-intensity peak at 20 position that corresponds to the most intensive peak of the rutile structure was registered at 450 °C. The capacitance of the composite was determined using cyclic voltammetry. It was found that the capacitance is dependent on calcination temperature and surface area of the carbon black support. The highest specific capacitance of about 700 F g -1 of composite was registered for RuO x H y supported on BP and calcined at 300 °C while four times lower values was obtained for RuO x H y supported on XC. The capacitance measurements indicated that XC-supported RuO x H y composite is highly porous while BP-supported one is more compact.

RUO2-TIO2 COATED TITANIUM ANODES OBTAINED BY THE SOL-GEL PROCEDURE AND THEIR ELECTROCHEMICAL BEHAVIOUR IN THE CHLORINE EVOLUTION REACTION

Abstract TiO2 and RuO2 sols were obtained from RuCl3 and TiCl3 aqueous solutions by condensation and forced hydrolysis at elevated temperature. The Ti supported coatings were obtained by the sol–gel method using a sol mixture in which the metal content was Ru(40%)–Ti(60%). The crystal structure of the solid phase of the sols and their mixtures was examined by X-ray diffraction. The surface and morphology of the coatings were characterized by scanning electron microscopy and scanning tunneling microscopy. Polarization measurements and cyclic voltammetry were used to obtain information about the electrochemical properties of the obtained anodes. An accelerated corrosion test was applied to quantify the anode stability for the chlorine evolution reaction. A stability comparison of the anodes shows a considerably higher lifetime for sol–gel coated anodes than for those obtained by the usual thermal decomposition method.

The influence of the aging time of RuO2 and TiO2 sols on the electrochemical properties and behavior for the chlorine evolution reaction of activated titanium anodes obtained by the sol-gel procedure

Abstract The influence of the aging time of RuO 2 and TiO 2 sols used for the preparation of (40% RuO 2 +60% TiO 2 )/Ti anodes by the sol-gel procedure on the electrochemical properties and behavior for the chlorine evolution reaction of obtained anodes was studied. The electrochemical (active) surface area of the anode coatings was examined by cyclic voltammetry. The electrocatalytic activity and stability of obtained anodes for the chlorine evolution reaction were investigated by polarization measurements and accelerated stability test. The dependence of electrochemical properties of obtained activated titanium anodes on RuO 2 and TiO 2 sol particle size was established.

The effect of the addition of colloidal iridium oxide into sol–gel obtained titanium and ruthenium oxide coatings on titanium on their electrochemical properties

Electrochemical properties of sol-gel processed Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings on titanium substrate were investigated using cyclic voltammetry, polarization measurements and electrochemical impedance spectroscopy and compared to the properties of Ti(0.6)Ru(0.4)O(2) coating. The role of iridium oxide in the improvement of the electrocatalytic, capacitive and stability properties of titanium anodes activated by a RuO(2)-TiO(2) coating is discussed. The oxide sols were prepared by forced hydrolysis of the metal chlorides. The characterization by dynamic light scattering and X-ray diffraction showed that polydisperse oxide sols were obtained with the particles tending to form agglomerates. The presence of IrO(2) causes a suppression of the X-ray diffraction peaks of TiO(2) and RuO(2) in the sol-gel prepared Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings. The IrO(2)-containing coatings had an enhanced charge storage ability and activity for the oxygen evolution reaction (OER) in comparison to Ti(0.6)Ru(0.4)O(2) coating. The voltammogram of the Ti(0.6)Ir(0.4)O(2)/Ti electrode showed well-resolved peaks related to Ir redox transitions, which are responsible for the enhanced charge storage ability of IrO(2)-containing coatings. Redox transitions of Ir were also registered in the high-frequency domain of the ac impedance spectra of the coatings as a semicircle with characteristics insensitive to the electrolyte composition and to the electrode potential prior to OER. However, the semicircle characteristics were different for the two IrO(2)-containing coatings, as well as at potentials outside the OER in comparison to those at which the OER occurs.

The Influence of the Aging Time of RuO2 Sol on the Electrochemical Properties of the Activated Titanium Anodes Obtained by Sol-Gel Procedure

The influence of the aging time of RuO 2 sol on the electrochemical properties and behaviour in chlorine evolution reaction of RuO 2 /Ti and (40%RuO 2 + 60%TiO 2 )/Ti anodes obtained by sol-gel procedure was studied. The electrochemically active surface area of the anode coatings was examined by cyclic voltammetry. The electrocatalytic activity and anode stability in chlorine evolution reaction were investigated by polarization measurements and accelerated stability test. The dependence of electrochemical properties of obtained activated titanium anodes on RuO 2 particle size was established.

Protective ability and impedance response of sol–gel reversely transformed ceria conversion coating on aluminium

Ceria coating is formed on Al from the ceria sol prepared exclusively by forced hydrolysis of Ce(NO3)4, in order to test their ability to protect Al from corrosion. The characterization of sol–gel-processed ceria coating and coating/Al assembly brings new issues on Al corrosion and protection caused by unique properties of the sol–gel coating. The corrosion behaviour of bare Al and Al/CeO2 is investigated by the electrochemical impedance spectroscopy (EIS) during the exposure to NaCl aqueous solution. The morphology and composition of the samples are examined by scanning electron microscopy and energy dispersive spectroscopy. EIS data showed greater corrosion resistance of CeO2-coated aluminium in comparison to bare Al at long exposure times. CeO2 coating does not hinder completely the corrosion processes on Al. The Al beneath CeO2 coating is subjected to intrinsic formation of a uniform protective coating/Al interphase, cross-linked by AlO(OH) fibre-like structures. They appear created by corrosive medium from the coating reversely gelled by NaCl solution. As the fibre network is created during exposure, Al becomes better protected than by spontaneous formation of porous passive layer of Al(OH)3 on bare aluminium. Sol–gel ceria coatings thus improve corrosion resistance of aluminium during prolonged exposure to corrosive medium.

High performance alkyd resins synthesized from postconsumer PET bottles

The glycolytic recycling of waste PET presents a challenge for the production of secondary value-added products, such as alkyd resins. A way to overcome the unsatisfactory mechanical, drying and chemical resistance properties of alkyds obtained from difunctional glycolyzates was proposed. Waste PET was glycolyzed using multifunctional alcohols: glycerol (G), trimethylolethane (TME), trimethylolpropane (TMP) and pentaerythritol (PE), giving tetra- and hexa-functional glycolyzates and, for comparison, using diethylene glycol (DEG), propylene glycol (PG) and dipropylene glycol (DPG) giving di-functional glycolyzates. The obtained glycolyzates were examined by 1H and 13C NMR, FTIR spectroscopy and elemental analysis and further used in the synthesis of alkyd resins. The properties of the prepared alkyd resins (acid, hydroxyl and iodine values, color, average molar masses and molar mass distributions, viscosity, drying time, hardness, flexibility, gloss, adhesion and chemical resistance) were investigated with respect to the functionality and the structure of the used glycolyzates. Alkyd resins derived from multifunctional glycolyzates (TME and TMP) showed considerably enhanced properties compared to those produced from difunctional glycolyzates and also to conventional general purpose resins.

Morphology and Capacitive Properties of [RuOxHy/Low Surface Area Carbon Black] Composite Materials Prepared by Sol Gel Procedure

The morphology and the capacitive properties of carbon supported hydrous ruthenium oxide (RuOxHy/C), prepared by impregnation of low-surface area carbon black VulcanÒ XC-72 R with solid phase of RuOxHy sol, were investigated by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The oxide sols of different ageing times, prepared by forced hydrolysis of RuCl3, were used for composite preparation. The prepared composites show considerably higher capacitance values in acid electrolyte if compared to carbon black support. Microscopic investigations show that the extent of impregnation and the composite surface appearance depend on ageing time. The composite capacitance increases with ageing time of oxide sol. A gradual decrease in capacitance of thermally untreated composite with charging/discharging cycles was registered, which appears to be related to the extent of impregnation, too. Electrochemical impedance spectroscopy measurements indicate an in-depth capacitance distribution through the composite layer. It was found that NafionÒ layer, used to ensure the adhesion of the composite layer to the current collector, influenced the composite impedance behavior, especially on the oxide-rich parts of the composite surface.

The Influence of Oxide Sol Properties on the Capacitive Behaviour of Carbon Supported Hydrous Ruthenium Oxide

Carbon supported hydrous ruthenium oxide was prepared by an ultrasonic threatment of carbon black-RuOxHy sol mixture (impregnation). Black Pearl 2000 was used as a supporting material, while an oxide sol was prepared by forced hydrolysis of hydrous RuCl3. The influence of the RuOxHy sol aging time and the amount of oxide solid phase in the impregnating medium on the capacitive behavior of prepared carbon supported hydrous ruthenium oxide was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The oxide amount in the composite increases with increasing concentration of oxide particles in the impregnating medium. The composite specific capacitance decreases with increasing aging time of oxide sol, while increases with increasing concentration of oxide particles in the impregnating medium. Transition line model fits well the composite impedance behavior indicating a distinctive capacitive response of the inner and the outer composite active surface. This distinction becomes more pronounced as the amount of oxide in the composite increases.

Titanium coated with high-performance nanocrystalline ruthenium oxide synthesized by the microwave-assisted sol-gel procedure

Ruthenium oxide coating on titanium was prepared by the sol–gel procedure from well-defined colloidal oxide dispersions synthesized by the microwave (MW)-assisted hydrothermal route under defined temperature and pressure heating conditions. The dispersions were characterized by dynamic light scattering (DLS) measurements and scanning electron microscopy (SEM). The electrochemical properties were analyzed as capacitive performances gained by cyclic voltammetry and electrochemical impedance spectroscopy and as the electrocatalytic activity for oxygen evolution from acid solution. The obtained dispersions were polydisperse and contained regular particles and agglomerates of increasing surface energy and decreasing particle size as the MW-assisted heating conditions were intensified. Owing to these features of the precursor dispersions, the obtained coatings had considerably improved capacitive performances and good electrocatalytic activity for oxygen evolution at high overpotentials.