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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 electrochemical characteristics of Ti(0.6)Ir(0.4)O(2)/Ti and Ti(0.6)Ru(0.4)O(2)/Ti anodes prepared by the sol gel procedure from the corresponding oxide sols, obtained by force hydrolysis of the corresponding metal chlorides, were compared. The voltammetric properties in H(2)SO(4) solution indicate that Ti(0.6)Ir(0.4)O(2)/Ti has more pronounced pseudocapacitive characteristics, caused by proton-assisted, solid state surface redox transitions of the oxide. At potentials negative to 0.0 V(SCE), this electrode is of poor conductivity and activity, while the voltammetric behavior of the Ti(0.6)Ru(0.4)O(2)/Ti electrode is governed by proton injection/ejection into the oxide structure. The Ti(0.6)Ir(0.4)O(2)/Ti electrode had a higher electrocatalytical activity for oxygen evolution, while the investigated anodes were of similar activity for chlorine evolution. The potential dependence of the impedance characteristics showed that the Ti(0.6)Ru(0.4)O(2)/Ti electrode behaved like a capacitor over a wider potential range than the Ti(0.6)Ir(0.4)O(2)/Ti electrode, with fully-developed pseudocapacitive properties at. potentials positive to 0.60 V(SCE). However, the impedance characteristics of the Ti(0.6)Ir(0.4)O(2)/Ti electrode changed with increasing potential from resistor-like to capacitor-like behavior.

Two samples of commercial multi-walled carbon nanotubes (Sigma-Aldrich and Sun Nanotech) and a sample of carbon black (Vulcan XC-72R) were investigated in raw state and after the activation in nitric and sulfuric acid by ultrasound agitation. Atomic force microscopy revealed that activated Sigma-Aldrich nanotubes are straight with corrugated walls (bamboo-like structure), while Sun Nanotech nanotubes are tortuous with smooth walls. Fourier transform infrared spectroscopy showed that abundance of oxygen-containing functional groups was formed on both Sigma-Aldrich and Sun Nanotech carbon nanotubes, as well as on carbon black surfaces. Electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the electrochemically active surface area of all carbon samples is expanded, charge storage ability is enhanced and the electron-transfer kinetics, probed by Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple, is promoted upon activation. The characteristics of carbon nanotubes were superior to Carbon black. Morphology of the carbon nanotubes was found to be important; nanotubes with corrugated walls showed faster electron-transfer and pseudocapacitive redox kinetics than nanotubes with smooth walls. This was explained by the higher proportion of edge and defect sites, which are known as more electrochemically active than the walls of uniform graphene structure.

The changes in capacitive behavior of C/H(x)RuO(y) composite material prepared by impregnating the Vulcan (R) XC 72R carbon black with oxide sols of different particle size are investigated as the electrolyte penetrates through the thin layer of the Nafion (R)-covered composite. The techniques of cyclic voltammetry and electrochemical impedance spectroscopy are used. Results of the investigation reveal the influence of potential cycling and the exposure time to the electrolyte on registered capacitive characteristics of composite. The cycling in a wide potential range causes the decrease in energy storage ability which depends on oxide particle size. Impedance measurements, however, show that the ability initially decreases and subsequently increases during exposure to the electrolyte as the consequence of the presence of Nafion (R) top-layer. Due to wettability and resistance issues, Nafion (R) top-layer can affect the pseudo-capacitive characteristics, and the energy storage ability of the composite consequently decreases.

The electrochemical characteristics of a mixture of Pt-black and WC powders and its catalytic activity for methanol and formic acid oxidation were investigated in acid solution. XRD and AFM measurements revealed that the WC powder employed for the investigation was a single-phase material consisting of crystallites/spherical particles of average size of about 50 nm, which were agglomerated into much larger particles. Cyclic voltammetry showed that the WC underwent electrochemical oxidation, producing tungstate species. In the case of the mixed Pt + WC powders, the tungstate species were deposited on the Pt as a thin film of hydrous tungsten oxide. Enhanced hydrogen intercalation in the hydrous tungsten oxide was observed and it was proposed to be promoted in mixed powders by the presence of hydrogen adatoms on bare Pt sites. The determination of Pt surface area in the Pt + WC layer by stripping of underpotentially deposited Cu revealed that the entire Pt surface was accessible for underpotential deposition of Cu. Investigation of the electrochemical oxidation of methanol and formic acid on Pt + WC and pure Pt layers did not indicate electrocatalytic promotion due to the presence of WC., U radu su ispitivane elektrohemijske karakteristike smeše prahova Pt i WC i njena katalitička aktivnost za reakcije oksidacije metanola i mravlje kiseline u kiselom rastvoru. Analiza rezultata difrakcije X-zraka (XRD) i mikroskopije atomskih sila (AFM) pokazuju da je prah WC jednofazni materijal sa prosečnom veličinom kristalita od oko 50 nm, koji su aglomerisani u mnogo veće čestice. Ciklična voltametrija ukazuje na to da WC podleže oksidaciji kojom nastaju volframatne vrste. U slučaju smeše prahova Pt i WC, volframatne vrste najverovatnije se talože na Pt u obliku tankog sloja hidratisanih oksida volframa. Primećeno je povećanje interkalacije vodonika u sloju hidratisanih volframata i pretpostavlja se da prisustvo adatoma vodonika na površini Pt potpomaže proces vodonične interkalacije. Određivanje površine Pt u sloju Pt + WC desorpcijom monosloja Cu taloženog na potpotencijalima ukazuje da je čitava površina Pt dostupna za taloženje atoma Cu. Ispitivanje elektrohemijskih reakcija oksidacije metanola i mravlje kiseline na sloju smeše Pt + WC i sloju čiste Pt ukazuje da prisustvo praha WC ne utiče na elektrokatalitička svojstva Pt.

The photoelectrochemical properties of a sol-gel prepared titanium oxide coating applied onto a Ti substrate were investigated. The oxide coating was formed from an inorganic sol thermally treated in air at 350°C. The coating consisted of agglomerates of narrow size distribution around 100 nm. The photoelectrochemical characteristics were evaluated by investigating the changes in the open circuit potential, current transients and impedance characteristics of a Ti/TiO2 electrode upon illumination by UV light in H2SO4 solution and in the oxidation of benzyl alcohol. The electrode was found to be active for photoelectrochemical reactions in the investigated solutions., Fotoelektrohemijska svojstva titan-oksida dobijenog sol-gel portupkom ispitivana su na oksidnoj prevlaci nanetoj na titansku podlogu. Prevlaka je termički tretirana u vazduhu na temperaturi od 350°C. Prevlaka se sastoji od zrna ujednačene raspodele po veličini od oko 100 nm. Fotoelektrohemijske karakteristike ustanovljene su ispitivanjem promena potencijala otvorenog kola, vremenske zavisnosti struje i impedansnih karakteristika Ti/TiO2 elektrode pri osvetljenosti UV svetlošću u rastvoru H2SO4 i pri oksidaciji benzil-alkohola. Ustanovljena je fotoaktivnost elektrode u ispitivanim sistemima.

The results of an investigation of the capacitive characteristics of sol-gel-processed titanium- and carbon-supported electrochemically active noble metal oxides, as representatives of porous electrode materials, are presented in the lecture. The capacitive properties of these materials were correlated to their composition, the preparation conditions of the oxides and coatings, the properties of the carbon support and to the composition of the electrolyte. The results of the electrochemical test methods, cyclic voltammetry and electrochemical impedance spectroscopy, were employed to resolve the possible physical structures of the mentioned porous materials, which are governed by the controlled conditions of the preparation of the oxide by the sol-gel process., U okviru predavanja su prikazani rezultati ispitivanja kapacitivnih karakteristika elektrohemijski aktivnih prevlaka oksida plemenitih metala formiranih na titanskom nosaču i kompozitnih ugljenično-oksidnih materijala kao najčešćih tipova planarnih poroznih elektroda. Kapacitivna svojstva ovih elektroda ispitivana su u funkciji njihovog sastava, uslova pod kojima su dobijeni oksidi i prevlake, karakteristika ugljeničnog nosača i sastava elektrolita, metodama ciklične voltametrije i spektroskopije elektrohemijske impedancije. Rezultati elektrohemijskih metoda korelisani su sa mogućom strukturom ovih materijala koju definiše kontrolisani proces dobijanja oksida sol-gel postupkom.

Electrochemical properties and porous-structure-dependent capacitive ability of commercial carbon blacks, Black Pearls 2000® (BP) and Vulcan® XC 72R (XC), were investigated in H2SO4 solution by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The capacitance in-depth profile is correlated to microscopic appearance of carbon blacks in the form of a thin layer applied over Au substrate from water suspensions of BP and XC. The capacitance calculated from voltammetric charge was found to depend on the sweep rate, due to porosity of investigated materials. Impedance (EIS) characteristics upon frequency-dependent charge/discharge process indicate transmission line electric behavior of BP and XC. Capacitance and resistance values obtained by simulations of EIS data, enabled estimation of capacitance and resistance profile throughout carbon black porous electrodes. Capacitance of BP carbon layer increases going from the outer surface towards the bulk of the layer. External capacitance originates from capacitive characteristics of the macroscopic surface consisting of relatively large agglomerates, while internal capacitance originates from "inner" surface of micro-porous agglomerates. Contrary to BP, opposite distribution of the total capacitance to external and internal part was found for XC, caused by its loose structure and considerably lower real surface area in comparison to BP. The XC morphology makes additionally the pseudocapacitive contribution of surface functionalities more pronounced, which indirectly shifts also the "internal" double-layer capacitive response to higher frequencies through the effect of increased wettability of the layer. Thus, the capacitance of XC surface directly exposed to the electrolyte is larger than that of the inner one, which makes it a "fully-utilized" capacitor, while increased capacitive performance of BP emerges only at very low frequencies of charging/discharging process.

The properties of activated titanium anodes, RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti, prepared from oxide sols by the sol-gel procedure, are reviewed. RuO2 and TiO2 sols were synthesized by forced hydrolysis of the corresponding chlorides in acid medium. The morphology of the prepared sols was investigated by transmission electron microscopy. The chemical composition of the RuO2 sol was determined by X-ray diffraction and thermogravimetric analysis. The loss of electrocatalytic activity of a RuO2-TiO2/Ti anode during an accelerated stability test was investigated by examination of the changes in the electrochemical characteristics in the potential region of the chlorine and oxygen evolution reaction, as well as on the open circuit potential. These electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and polarization measurements. The changes in electrochemical characteristics of the anode prepared by the sol-gel procedure were compared to the changes registered for an anode prepared by the traditional thermal decomposition of metal chlorides. The comparison indicated that the main cause for the activity loss of the sol-gel prepared anode was the electrochemical dissolution of RuO2, while in the case of thermally prepared anode the loss was mainly caused by the formation of an insulating TiO2 layer in the coating/Ti substrate interphase. The results of an accelerated stability test on RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti anodes showed that the ternary coating is considerably more stable than the binary one, which is the consequence of the greater stability of IrO2 in comparison to RuO2., U radu je dat je pregled svojstava aktiviranih titanskih anoda, RuO2-TiO2/Ti i RuO2--TiO2-IrO2/Ti, dobijenih sol-gel postupkom od neorganskih oksidnih solova. RuO2 i TiO2 solovi dobijeni su forsiranom hidrolizom odgovarajućih hlorida metala u kiseloj sredini. Morfologija dobijenih solova ispitivana je transmisionom elektronskom mikroskopijom. Hemijski sastav RuO2 sola ispitivan je difrakcijom x-zraka i termogravimetrijskom analizom. Mehanizam gubitka elektrokatalitičke aktivnosti RuO2-TiO2/Ti anoda ispitivan je praćenjem promena elektrohemijskih svojstava anode u reakcijama izdvajanja hlora i kiseonika, kao i na potencijalu otvorenog kola, tokom degradacije anode. Ove elektro-hemijske karakteristike anode ispitivane su metodama ciklične voltametrije, spektroskopije elektrohemijske impedancije i polarizacionim merenjima. Promene u elektrohemijskim svojstvima anode dobijene sol-gel postupkom poređene su sa promenama koje su registrovane za RuO2-TiO2/Ti anodu dobijenu tradicionalnim postupkom termičke razgradnje hlorida metala. Na osnovu ovih ispitivanja proizilazi da je osnovni uzrok gubitka elektrokatalitičke aktivnosti anode dobijene sol-gel postupkom elektrohemijsko rastvaranje RuO2, dok je uzrok degradacije anode dobijene termičkom razgradnjom rast neprovodnog TiO2 sloja u međufazi prevlaka/titanska podloga. Rezultati ubrzanog testa stabilnosti RuO2-TiO2/Ti i RuO2-TiO2-IrO2/Ti anode pokazuju da je trojna prevlaka znatno stabilnija od dvojne, zbog veće stabilnosti oksida iridijuma u poređenju sa oksidom rutenijuma.

The properties of activated titanium anodes, RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti, prepared from oxide sols by the sol-gel procedure, are reviewed. RuO2 and TiO2 sols were synthesized by forced hydrolysis of the corresponding chlorides in acid medium. The morphology of the prepared sols was investigated by transmission electron microscopy. The chemical composition of the RuO2 sol was determined by X-ray diffraction and thermogravimetric analysis. The loss of electrocatalytic activity of a RuO2-TiO2/Ti anode during an accelerated stability test was investigated by examination of the changes in the electrochemical characteristics in the potential region of the chlorine and oxygen evolution reaction, as well as on the open circuit potential. These electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and polarization measurements. The changes in electrochemical characteristics of the anode prepared by the sol-gel procedure were compared to the changes registered for an anode prepared by the traditional thermal decomposition of metal chlorides. The comparison indicated that the main cause for the activity loss of the sol-gel prepared anode was the electrochemical dissolution of RuO2, while in the case of thermally prepared anode the loss was mainly caused by the formation of an insulating TiO2 layer in the coating/Ti substrate interphase. The results of an accelerated stability test on RuO2-TiO2/Ti and RuO2--TiO2-IrO2/Ti anodes showed that the ternary coating is considerably more stable than the binary one, which is the consequence of the greater stability of IrO2 in comparison to RuO2., U radu je dat je pregled svojstava aktiviranih titanskih anoda, RuO2-TiO2/Ti i RuO2--TiO2-IrO2/Ti, dobijenih sol-gel postupkom od neorganskih oksidnih solova. RuO2 i TiO2 solovi dobijeni su forsiranom hidrolizom odgovarajućih hlorida metala u kiseloj sredini. Morfologija dobijenih solova ispitivana je transmisionom elektronskom mikroskopijom. Hemijski sastav RuO2 sola ispitivan je difrakcijom x-zraka i termogravimetrijskom analizom. Mehanizam gubitka elektrokatalitičke aktivnosti RuO2-TiO2/Ti anoda ispitivan je praćenjem promena elektrohemijskih svojstava anode u reakcijama izdvajanja hlora i kiseonika, kao i na potencijalu otvorenog kola, tokom degradacije anode. Ove elektro-hemijske karakteristike anode ispitivane su metodama ciklične voltametrije, spektroskopije elektrohemijske impedancije i polarizacionim merenjima. Promene u elektrohemijskim svojstvima anode dobijene sol-gel postupkom poređene su sa promenama koje su registrovane za RuO2-TiO2/Ti anodu dobijenu tradicionalnim postupkom termičke razgradnje hlorida metala. Na osnovu ovih ispitivanja proizilazi da je osnovni uzrok gubitka elektrokatalitičke aktivnosti anode dobijene sol-gel postupkom elektrohemijsko rastvaranje RuO2, dok je uzrok degradacije anode dobijene termičkom razgradnjom rast neprovodnog TiO2 sloja u međufazi prevlaka/titanska podloga. Rezultati ubrzanog testa stabilnosti RuO2-TiO2/Ti i RuO2-TiO2-IrO2/Ti anode pokazuju da je trojna prevlaka znatno stabilnija od dvojne, zbog veće stabilnosti oksida iridijuma u poređenju sa oksidom rutenijuma.

The electrochemical characteristics of a mixture of Pt-black and WC powders and its catalytic activity for methanol and formic acid oxidation were investigated in acid solution. XRD and AFM measurements revealed that the WC powder employed for the investigation was a single-phase material consisting of crystallites/spherical particles of average size of about 50 nm, which were agglomerated into much larger particles. Cyclic voltammetry showed that the WC underwent electrochemical oxidation, producing tungstate species. In the case of the mixed Pt + WC powders, the tungstate species were deposited on the Pt as a thin film of hydrous tungsten oxide. Enhanced hydrogen intercalation in the hydrous tungsten oxide was observed and it was proposed to be promoted in mixed powders by the presence of hydrogen adatoms on bare Pt sites. The determination of Pt surface area in the Pt + WC layer by stripping of underpotentially deposited Cu revealed that the entire Pt surface was accessible for underpotential deposition of Cu. Investigation of the electrochemical oxidation of methanol and formic acid on Pt + WC and pure Pt layers did not indicate electrocatalytic promotion due to the presence of WC.

The capacitive properties of titanium electrodes with an active porous RuO2 coating were investigated in H2SO4 and NaCl solution by cyclic voltammetry and electrochemical impedance spectroscopy. Electrodes with two different masses of coating (thin and thick coating) were prepared from an ink suspension of the oxide synthesized by hydrolysis of ruthenium-ethoxide in ethanolic solution. The capacitive characteristics were found to be dependent on the coating mass and the electrolyte composition. It was shown that the impedance data of the prepared electrodes, registered at the open circuit potential, can be interpreted by a transmission line model of the equivalent electrical circuit. In this interpretation, the number of parallel branches containing resistor and capacitor in series is different for thin and thick coatings and in different electrolytes. More branches were required to describe the impedance behavior of the thick coating and to simulate the impedance data in NaCl solution. Simulation of the impedance data with the transmission line model of the equivalent circuit was also used to analyze the distribution of capacitance throughout the porous coating. The simulation indicated a more pronounced contribution of the capacitance of the outer coating layer to the total coating capacitance in the case of the proton-rich electrolyte. On the other hand, the presence of chloride ions in the electrolyte promoted a charging process at the inner coating surface, which is hardly accessible to the electrolyte.

The characteristics of a ternary oxide coating, on titanium, which consisted of TiO2, RuO2 and IrO2 in the molar ratio 0.6:0.3:0.1, calculated on the metal atom, were investigated for potential application for cathodic protection in a seawater environment. The oxide coatings on titanium were prepared by the sol-gel procedure from a mixture of inorganic oxide sols, which were obtained by forced hydrolysis of metal chlorides. The morphology of the coating was examined by scanning electron microscopy. The electrochemical properties of activated titanium anodes were investigated by cyclic voltammetry and polarization measurements in a H2SO4- and NaCl-containing electrolyte, as well as in seawater sampled on the Adriatic coast in Tivat, Montenegro. The anode stability during operation in seawater was investigated by the galvanostatic accelerated corrosion stability test. The morphology and electrochemical characteristics of the ternary coating are compared to that of a sol-gel-prepared binary Ti0.6Ru0.4O2 coating. The activity of the ternary coating was similar to that of the binary Ti0.6Ru0.4O2 coating in the investigated solutions. However, the stability in seawater is found to be considerably greater for the ternary coating., Karakteristike trojne oksidne prevlake na titanu, koja se sastoji od TiO2, RuO2 i IrO2 u molskom odnosu 0.6:0.3:0.1 računato na atom metala, ispitivane su sa ciljem potencijalne primene za katodnu zaštitu u morskoj vodi. Oksidna prevlaka na titanu formirana je sol-gel postupkom iz smeše neorganskih oksidnih solova, koji su dobijeni forsiranom hidrolizom hlorida metala. Morfologija prevlake je ispitivana skenirajućom elektronskom mikroskopijom, dok su elektrohemijska svojstva aktiviranih titankih anoda ispitivana metodom ciklične voltametrije i polarizacionim merenjima u rastvorima H2SO4, NaCl i u realnim uslovima, u morskoj vodi uzorkovanoj iz Jadranskog mora (Tivat, Crna Gora). Stabilnost anode tokom rada u morskoj vodi ispitivana je galvanostatski, ubrzanim testom stabilnosti. Dobijene prevlake upoređene su sa dvojnom Ti0,6Ru0,4O2 prevlakom, u pogledu morfologije i elektrohemiskih karakteristika. Pokazano je da su trojna i dvojna prevlaka slične aktivnosti u ispitivanim rastvorima. Međutim, u morskoj vodi stabilnost trojne prevlake je znatno veća.

Electroactive oxide coatings on titanium, known in industrial chlorine production as dimensionally stable anodes (DSA), are of limited service life owing to the dissolution of active oxide, but also due to low corrosion stability of titanium, at high anodic potentials and elevated temperatures. In order to improve the anode stability, ternary carbide, Ti3SiC2, could be a promising material for the coating support, since chemical corrosion stability of Ti3SiC2 is significantly higher if compared to Ti. In this work, the possibility of the sol-gel preparation of RuO2-TiO2 coating on Ti3SiC2 is investigated and comparison of the basic characteristics of sol-gel processed oxide coating, Ru0.5Ti0.5O2, applied onto Ti3SiC2 and Ti, is reported. Microscopic investigation of the coating surface showed that considerably less cracked coating is formed onto the Ti3SiC2 support. Slightly higher voltammetric currents are registered for Ti3SiC2-supported coating in H2SO4 and NaCl solution. The activity for chlorine evolution is higher, while the currents of oxygen evolution reaction are lower for Ru0.5Ti0.5O2/Ti3SiC 2 anode in comparison to Ru0.5Ti0.5O2/Ti anode. Even though these preliminary results on the basic electrochemical properties of Ru0.5Ti0.5O2/Ti3SiC 2 anode and chemical stability of Ti3SiC2 are promising, the accelerated stability test in NaCl solution showed that coated Ti3SiC2 is not anodically stable and lasts considerably shorter than Ru0.5Ti0.5O2/Ti anode prepared and tested under the same conditions.

Preparation of hydrous ruthenium oxide/carbon black nanocomposite material was performed by the impregnation method starting from hydrous RuO2 sol as a precursor. Black Pearls 2000 (R) (BP) and Vulcan (R) XC-72 R (XC) was used as supporting materials. Chemical and structural characterization of the precursor and the composites was performed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRFS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These techniques showed hydrous and amorphous structure of the oxide impregnated into the carbon support. The capacitive properties of both carbon supporting materials and composites will be discussed in forthcoming parts of this paper.

Preparation of hydrous ruthenium oxide/carbon black nanocomposite material was performed by the impregnation method starting from hydrous RuO2 sol as a precursor. Black Pearls 2000 (R) (BP) and Vulcan (R) XC-72 R (XC) was used as supporting materials. Capacitive properties of BP/RuO2 and XC/RuO2 composites were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in H2SO4 solution. Overall capacitance and capacitance profile throughout composite porous layer depend on carbon black real surface area and the concentration of oxide phase in the impregnating medium, as well as on ageing time of oxide sol.

Preparation of hydrous ruthenium oxide/carbon black nanocomposite material was performed by the impregnation method starting from hydrous RuO2 sol as a precursor. Black Pearls 2000 (R) (BP) and Vulcan (R) XC-72 R (XC) was used as supporting materials. Chemical and structural characterization of the precursor and the composites was performed by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectroscopy (EDXRFS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These techniques showed hydrous and amorphous structure of the oxide impregnated into the carbon support. The capacitive properties of both carbon supporting materials and composites will be discussed in forthcoming parts of this paper.

Preparation of hydrous ruthenium oxide/carbon black nanocomposite material was performed by the impregnation method starting from hydrous RuO2 sol as a precursor. Black Pearls 2000 (R) (BP) and Vulcan (R) XC-72 R (XC) was used as supporting materials. Capacitive properties of supporting materials were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in H2SO4 solution. Overall capacitance and capacitance profile throughout carbon black porous layer depend on its real surface area and morphology.

Electrocatalytic properties of RuO 2 /Ti anode with different coating masses, which are prepared by the alkoxide sol–gel procedure, are investigated in chlorine and oxygen evolution reactions by polarization measurements and electrochemical impedance spectroscopy in H 2 SO 4 and NaCl electrolytes. According to polarization measurements, the activity of anodes at overpotentials below 100 mV is independent of coating mass. However, impedance measurements above 100 mV reveal changes in the activity of anodes in chlorine evolution reaction for different coating masses. The diffusion limitations related to the evolved chlorine are registered in low-frequency domain at 1.10 V (SCE), diminishing with the increase in potential to the 1.15 V (SCE). The observed impedance behavior is discussed with respect to the activity model for activated titanium anodes in chlorine evolution reaction involving formation of gas channels within porous coating structure. Gas channels enhance the mass transfer rate similarly to the forced convection, which also increases the activity of anode. This is more pronounced for the anode of greater coating mass due to its more compact surface structure. The more compact structure appears to be beneficial for gas channels formation.

Titanium anodes with an active RuO2 coating of two different thicknesses were prepared from the oxide suspended in ethanol ("ink" method), while the oxide itself was synthesized by the hydrolysis of ruthenium ethoxide in an ethanolic solution (alkoxide route). The morphology of prepared oxide was examined by scanning electron microscopy. The electrochemical properties of the prepared Ti/RuO2 anodes, involving their cyclic voltammetric behavior in H2SO4 and NaCl solutions, activity in the chlorine and oxygen evolution reaction, impedance behavior in H2SO4, and stability during electrolysis in dilute chloride solutions, were investigated. The performances of the anodes are compared to those of a Ti/RuO2 anode prepared by the sol-gel procedure from an oxide sol obtained by the forced hydrolysis of ruthenium chloride in acid solution. The anodes prepared via the alkoxide route showed a higher capacitance and activity for the chlorine evolution reaction than the anode prepared by the inorganic sol-gel procedure. The results of the stability test showed that the utilization of the coating active material is better when the anodes were prepared via the alkoxide route than via the inorganic sol-gel procedure, particularly for anodes with a smaller mass of coating. The different rates of loss of activity indicate a degradation mechanism for the anodes prepared via the alkoxide route in which electrochemical dissolution of RuO2 from the coating surface prevails over the growth of an insulating TiO2 layer in the coating/Ti substrate interphase. The effect of RuO2 dissolution from the coating surface increases with increasing coating mass., Titanske anode sa aktivnom prevlakom od oksida rutenijuma dve različite debljine, formirane su od oksida dobijenog hidrolizom rutenijum(III)-etoksida u etanolskom rastvoru ("ink" metoda). Morfologija dobijenog oksida ispitivana je skenirajućom elektronskom mikroskopijom. Ispitivana su elektrohemijska svojstva formiranih anoda, koja podrazumevaju ciklično-voltametrijsko ponašanje u rastvorima H 2SO4 i NaCl, aktivnost u reakcijama izdvajanja hlora i kiseonika, impedansno pona- šanje i stabilnost tokom elektrolize razblaženih rastvora hlorida. Karakteristike dobijenih anoda upoređene su sa karakteristikama anode formirane sol-gel postupkom iz oksidnog sola dobijenog forsiranom hidrolizom rutenijum(III)-hlorida u kiseloj sredini (5 mol dm-3HCl). Anode formirane alkoksidnim postupkom imaju veću kapacitivnost i aktivnost za reakciju izdvajanja hlora od anode dobijene sol-gel postupkom iz neorganskog sola. Rezultati testa stabilnosti u rastvoru hlorida pokazuju da je iskorišćenje aktivnog materijala prevlake takođe bolje kod anoda dobijenih alkoksidnim postupkom, naročito za anodu sa manjom debljinom prevlake. Rezultati ukazuju na to da u mehanizmu gubitka aktivnosti anoda dobijenih alkoksidnim postupkom elektrohemijsko rastvaranje oksida rutenijuma sa površine prevlake preovlađuje u odnosu na rast izolatorskog sloja oksida titana u međufazi prevlaka/ titanska podloga. Efekt rastvaranja RuO2 sa površine je izraženiji kod prevlake veće debljine.

Aktivirane titanske anode, Ti/RuO2 TiO2, i RuO2/ugljenični kompoziti dobijeni su sol gel postupkom od neorganskih oksidnih solova. RuO2 i TiO2 solovi dobijeni su forsiranom hidrolizom RuCl3 u vodenom rastvoru HCl. Morfologija dobijenih solova ispitivana je transmisionom elektronskom mikroskopijom. Hemijski satav RuO2 sola i od njega dobijenih RuO2/ugljeničnih kompozita impregnacijom komercijalnih ugljeničnih prahova ispitivana je difrakcijom x zraka i termogravimetrijskom analizom. Ova ispitivanja pokazuju da su sitne oksidne čestice sačinjene od hidratisanog oksida. Morfologija kompozita i ugljeničnih prahova ispitivana je skenirajućom elektronskom mikroskopijom koja ukazuje na prisustvo oksida u impregniranom ugljeničnom prahu. Mehanizam gubitka elektrokatalitičke aktivnosti Ti/RuO2 TiO2 anoda ispitivan je praćenjem promena elektrohemijskih svojstava anode u reakcijama izdvajanja hlora i kiseonika, kao i na potencijalu otvorenog kola, u rastvorima NaCl i H2SO4 tokom degradacije anode. Ove elektrohemijske karakteristike anode ispitivane su metodama ciklične voltametrije, spektroskopije elektrohemijske impedancije i polarizacionim mere¬njima. Stabilnost anoda je ispitivana ubrzanim testom stabilnosti u ras¬tvoru NaCl. Promene u elektrohemijskim svojstvima anode dobijene sol gel postupkom pore¬đene su sa promenama koje su registrovane za Ti/RuO2 TiO2 anodu dobijenu tradicionalnim postupkom termičke razgradnje hlorida metala. Na osnovu pomenutih ispitivanja proizilazi da je osnovni uzrok gubitka elektro¬katalitičke aktivnosti anode dobijene sol gel postupkom elek¬trohemijsko rastvaranje RuO2, dok je uzrok degradacije anode dobijene termičkom razgra-dnjom rast neprovodnog TiO2 sloja u međufazi prevlaka/titanska podloga. Aktivnost Ti/RuO2 TiO2 anoda za reakciju oksidacije fenola ispitivana je u kiselom ras¬tvoru metodama ciklične voltametrije, hronoamperometrije i polarizacionim merenjima. Ustanovljeno je da se ova reakcija odigrava preko dva reakciona puta, koji daju p, Activated titanium anodes, Ti/RuO2 TiO2, and C/RuO2 composites were prepared from oxide sols by sol gel procedure. RuO2 and TiO2 sols have been synthesized by forced hydrolysis of RuCl3 in HCl water solution. Morphology of prepared sols was investigated by transmission electron microscopy. Chemical composition of RuO2 sol and C/RuO2 composites prepared by impregnation of commercial carbon blacks was investigated by x ray diffraction and thermogravimetric analysis. These investigations showed that fine hydrous oxide particles were formed. Morphology of composites and carbon blacks was investigated by scanning electron microscopy, which indicated the presence of oxide in the impregnated carbon blacks. The loss of Ti/RuO2 TiO2 anode electrocatalytic activity was investigated by examination of the changes in anode electrochemical characteristics for chlorine and oxygen evolution reaction, as well as on open circuit potential, in NaCl and H2SO4 solutions, during an accelerated stability test. These electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and polarization measurements. Anode degradation was done by accelerated stability test in NaCl solution. The changes in electrochemical characteristics of the anode prepared by sol gel procedure were compared to the changes registered for the anode prepared by traditional thermal decomposition of metal chlorides.The comparison indicated that the main cause for the activity loss of sol gel prepared anode is electrochemical dissolution of RuO2, while in the case of thermally prepared anode the loss is mainly caused by the formation of an insulating TIO2 layer in the coating/Ti substrate interphase. The Ti/RuO2 TiO2 anode activity for phenol electrooxidation was investigated in acidic solution by cyclic voltammetry, current transients and polarization measurements. The oxidation proceeds via two reaction paths, with, strongly adherent to the electrocde surface, and qui

The deactivation process that leads to the end of titanium supported RuO2-TiO2 coating service life, for anodes prepared from RuO2 and TiO2 sols, as well as by the conventional thermal decomposition of RuCl3 and TiCl3, was investigated. The loss of electrocatalytic activity was registered by an accelerated stability test in 0.50 mol dm-3 NaCl electrolyte, while the changes in the electrochemical properties were monitored during the stability test by cyclic voltammetry, polarization measurements and electrochemical impedance spectroscopy in 1.0 mol dm-3 HClO 4 and in 0.50 mol dm-3 NaCl. The changes in anode behavior suggest that the essential cause for the deactivation of the anode prepared by the sol-gel procedure is the formation of an insulating TiO 2-rich layer at the coating surface due to the continuous dissolution of the Ru active species. However, the growth of the insulating TiO2 layer in the coating/Ti substrate interphase mainly causes deactivation of the thermally prepared anode. The deactivation mechanism appeared to be the consequence of the different morphology of the coatings prepared by two different procedures.

The morphology and the capacitive properties of carbon supported hydrous ruthenium oxide (RuOxHy/C), prepared by impregnation of low-surface area carbon black Vulcano (R) 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 Nafion (R) 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 morphology and the capacitive properties of carbon supported hydrous ruthenium oxide (RuOxHy/C), prepared by impregnation of low-surface area carbon black Vulcan® XC-72 R with solid phase of RuO xHy 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 RuCl 3, 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 Nafion® 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.

Polarization characteristics of titanium anodes, coated by active RuO2-TiO2 binary oxide using sol-gel preparation procedure and chloride thermal decomposition, in oxygen evolution reaction during anode electrolytic degradation were investigated in HClO4 solution. The accelerated electrolytic degradation of oxide coating has been performed in 3 mass% NaCl, pH 2. The anode prepared by sol-gel procedure is of better polarization characteristics than the anode prepared by thermal decomposition, which makes the former more suitable for the application in cathodic protection of metallic and steel constructions exposed to the sea water corrosion attacks., Polarizacione karakteristike titanskih anoda, aktiviranih RuO2-TiO2 prevlakom različitim postupcima, u reakciji izdvajanja kiseonika tokom elektrolitičke degradacije anode, ispitivane su u rastvoru HClO4. Ubrzana elektrolitička degradacija oksidne prevlake vršena je u 3 mas % rastvoru NaCl, pH 2. Utvrđeno je da anode aktivirane sol-gel postupkom imaju bolje polarizacione karakteristike od anoda dobijenih termičkom razgradnjom, odnosno pogodnija svojstva za potencijalnu primenu u katodnoj zaštiti metalnih i čeličnih konstrukcija izloženih korozivnom dejstvu morske vode.

Preparation of RuOxHy/carbon black nanocomposite material was performed by the impregnation method starting from RuOxHy 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 2θ 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 RuOxHy supported on BP and calcined at 300 °C while four times lower values was obtained for RuOxHy supported on XC. The capacitance measurements indicated that XC-supported RuOxHy composite is highly porous while BP-supported one is more compact.

In order to understand the role of TiO2 in the deactivation mechanism of an active RuO2–TiO2 coating, an additional TiO2 layer was introduced in the support coating interphase of regular Ti//[RuO2–TiO2 anode in one case and on the surface of the coating in the other. The electrochemical behavior of these, with TiO2 enriched, anodes was compared with the behavior of anodes with regular RuO2–TiO2 coatings, which were subjected to an accelerated stability test. A high-frequency semicircle in the complex plane plot obtained by electrochemical impedance spectroscopy, for a regular RuO2–TiO2 coating corresponds to TiO2 enrichment in the coating as a consequence of anode corrosion. In the case of the coatings with additional TiO2 layers, a high-frequency semicircle was not observed. The additional TiO2 layers increase the coating overall resistance and influence the coating impedance behavior at low frequencies. Similar equivalent electrical circuits were used to analyze the impedance behavior of coatings having an additional TiO2 layer at different position within RuO2–TiO2 coating., U cilju ispitivanja uloge titan-oksida u deaktivaciji RuO2–TiO2 prevlake na titanskoj podlozi, ispitivane su osobine anoda sa dodatnim slojem TiO2 u međufazi podloga prevlaka, odnosno na površini prevlake. Elektrohemijsko ponašanje ovih upoređeno je sa ponašanjem anoda sa uobičajenom RuO2–TiO2 prevlakom, kao i sa onima koje su bile podvrgnute ubrzanom testu stabilnosti. Pojava polukruga u visoko-frekventnoj oblasti u dijagramima u kompleksnoj ravni, koja je registrovana spektroskopijom elektrohemijske impedancije za uobičajene RuO2–TiO2 prevlake, a koja je posledica obogaćivanja prevlake sa TiO2 tokom njene deaktivacije, nije uočena kod anoda sa dodatim TiO2 slojem. Dodati TiO2 slojevi povećavaju omsku otpornost prevlake i utiču na impedancijsko ponašanje pri niskim frekvencijama. Za analizu impedancijskog ponašanja prevlaka sa dodatim TiO2 slojevima kao i uobičajenih RuO2–TiO2 prevlaka koje su deaktivirane korišćena su slična ekvivalentna električna kola.

The influence of different parameters (forced hydrolysis duration in the preparation of sols, alcohol addition in the sol mixture for application, as well as sol/alcohol mixture ageing time) on the morphology and electrochemical properties of RuO2-TiO2 coatings obtained by the sol-gel procedure is presented. The oxide sols were sharacterized by spectroscopic and microscopic methods (X-ray diffraction, TEM, etc). The morphology of the obtained coatings was examined by scanning tunneling microscopy, while the electrochemical properties were investigated by cyclic voltammetry polarization measurements, electrochemical impedance spectroscopy and the accelerated stability test. The greatest real surface area was obtained for coatings with the smallest RuO2 particles and largest TiO2 particles. Alcohol addition caused enlargement of the oxide grains and, consequently, a decrease in the real surface area. The same effects of oxide grain size were registered on electrochemically active surface area. The electrocatalytic activity of the obtained anodes for the chlorine evolution reaction increased with growth of the TiO2 particles, but depended on the RuO2 particle size to a small degree. The corrosion stability of the anode coatings consisting of the smallest RuO2 particles and largest TiO2 particles whis the greatest in the electrolysis of a sodium-chloride solution., Postupak dobijanja RuO2-TiO2 elektrohemijski aktivnih oksidnih prevlaka iz solova odgovarajućih oksida kao alternativa uobičajenom načinu formiranja prevlaka termičkom razgradnjom odgovarajućih hlorida i njihova karakterizacija predmet su ovog preglednog rada. Prvi deo rada daje pregled istraživanja koja su dovela do postupka dobijanja stabilnih solova RuO2 i TiO2 metodom forsirane hidrolize, kao i pregled karakterizacije dobijenih solova uglavnom spektroskopskim i mikroskopskim tehnikama (difrakcija X-zraka, STM, JEM i si). Pored toga, prikazani su i rezultati istraživanja pojedinih parametara procesa forsirane hidrolize, kao što su dužina trajanja hidrolize i sastav disperzne sredine, na osobine dobijenih so/ova. Drugi deo rada posvećen je dobijanju aktivnih prevlaka sol-gel postupkom, njihovoj detaljnoj karakterizaciji spektroskopskim, mikroskopskim i elektrohemijskim metodama, kao i uporednoj analizi njihovih osobina u odnosu na prevlake dobijene termičkom razgradnjom, posebno u elektrohemijskoj reakciji izdvajanja hlora. Posebna pažnja posvećena je istraživanju uticaja osobina solova-prekursora na osobine aktivnih prevlaka. Pokazano je da aktivne prevlake formirane sol-gel postupkom, bar na nivou laboratorijskih istraživanja, pokazuju određene prednosti u odnosu na prevlake formirane termičkim postupkom.

The influence of the addition of methanol, ethanol, 1-propanol and 2-propanol to the dispersing medium of a mixture of RuO2 and TiO2 sols on the electrochemically active surface area for proton exchange, as well as on the electrocatalytic activity for the chlorine evolution reaction (CER) of RuO2-TiO2/Ti electrode obtained by sol-gel procedure was investigated. The electrochemically active surface area was examined by cyclic voltammetry, while the analysis of the activity for the CER was performed by polarization measurements. The stability of the obtained anode coatings was also checked by an accelerated stability test. The anode properties depend on the number of C atoms in the alcohol molecule, as well as on the elapsed time between the preparation of the sols/alcohol mixture and its application onto the titanium support. The addition of alcohol increased the activity of the anodes for the CER, compared to those prepared without the addition, but their stability was smaller., U radu je ispitivan uticaj metanola, etanola, 1-propanola i 2-propanola, dodatih u disperznu sredinu RuO2-TiO2 smeše solova, na elektrohemijski aktivnu površinu i elektrokatalitičku aktivnost za reakciju izdvajanja hlora (RIH) RuO2-TiO2/Ti elektroda dobijenih sol-gel postupkom. Elektrohemijski aktivna površina ispitivana je metodom ciklične voltametrije, dok je aktivnost za RIH ispitivana polarizacionim merenjima. Takođe je i ubrzanim testom stabilnosti ispitivana postojanost dobijenih oksidnih prevlaka. Utvrđeno je da osobine dobijenih anoda zavise od broja ugljenikovih atoma u molekulu dodatog alkohola i vremena proteklog od pripreme smeše alkohola i solova do nanošenja smeše na titanski nosač. Uočeno je da dodatak alkohola prouzrokuje povećanje aktivnosti anoda za RIH u odnosu na anode dobijene bez dodavanja alkohola. Istovremeno, anode dobijene dodavanjem alkohola su manje stabilne od anoda dobijenih bez dodavanja alkohola.

The influence of the aging time of RuO2 and TiO2 sols used for the preparation of (40% RuO2+60% TiO2)/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 RuO2 and TiO2 sol particle size was established.

The effect of the addition of ethanol and 2-propanol to the dispersing phase of TiO2 and RuO2 sols mixture on the morphology and, consequently, on the electrochemical properties of the sol-gel obtained activated titanium anodes was investigated. The properties of the obtained anodes were compared to those obtained by the thermal decomposition of appropriate chloride salts. The morphology of the anode coatings was examined by scanning tunneling microscopy. The electrochemical behaviour was investigated by cyclic voltammetry and by polarization measurements. An accelerated stability test was used for the examination of the stability of the anodes under simultaneous oxygen and chlorine evolution reaction. A dependence of the anode stability on the type of added alcohol is indicated., U radu je ispitivan uticaj dodavanja etanola odnosno izopropanola u disperznu sredinu smeše solova TiO2 i RuO2 na morfologiju i elektrohemijske osobine aktiviranih titanskih anoda dobijenih sol-gel postupkom. Osobine ovako dobijenih anoda su poređene kako međusobno tako i sa osobinama anoda dobijenih termičkim postupkom iz hlorida rutenijuma i titana. Morfologija anodnih prevlaka ispitivana je skenirajućom tunelskom mikroskopijom, a elektrohemijsko ponašanje cikličnom voltametrijom i polarizacionim merenjima. Stabilnost anoda u paralelnim reakcijama izdvajanja kiseonika i hlora ispitivana je ubrzanim testom stabilnosti. Uočeno je da morfologija, elektrokatalitička aktivnost i stabilnost dobijenih anoda zavisi od vrste dodatog alkohola.

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.