On the stability of platinum-composite electrocatalysts prepared with different substrate materials

Cyclic voltammetry (CV) measurements were conducted and analyzed for a preliminary estimation of the stability of composite electrocatalysts based on Pt. The changes in CV currents of platinum nanoparticles supported on TiO2 were compared to the changes of those supported on commercial carbon. TiO2 was synthesized by sol-gel method and Pt was deposited from Pt colloidal dispersion synthesized by microwave-assisted polyol process. It was found that Pt component in both Pt/TiO2 and Pt/C behaves similarly with respect to stability and activity during the cycling. The loss in activity with cycling was linear and strongly depended on sweep rate, i.e., the relative loss is higher at lower sweep rates. The steady state activities for both electrocatalysts were reached at the level of 65 % of initial activity and required more than 100 voltammetric cycles

Electrocatalytic and Capacitive Properties of Ruthenium Oxide Based Electrodes

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 polioksifenilenski film na površini anode i rastvorne hinonska jedinjenja kao krajnje proizvode reakcije. Polioksifenilenski film inhibira reakciju oksidacije fenola. Karakteristike filma ispitivane su metodom spektro¬skopije elektrohemijske impedancije. Kapacitivne karakteristike RuO2/ugljeničnog kompozita ispitivane su metodama ciklične voltametrije i spektroskopije elektrohemijske impedancije u rastvoru H2SO4. Kapacitivnost i raspodela kapacitivnosti kroz porozni sloj kompozita zavise od realne površine ugljeničnog substrata i od koncentracije oksidne faze u impregnirajućoj sredini, kao i od vremena formiranja oksidnog sola korišćenog za impregnaciju.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 quinone compounds as the final reaction products. Polyoxyphenylene film inhibits phenol oxidation. Characteristics of the film were investigated by electrochemical impedance spectroscopy. Capacitive properties of C/RuO2 composites were investigated by cyclic volta¬mmetry 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

Microwave Synthesis of Crystalline Ruo2 Supercapacitor Materials

One-step simple temperature-controlled microwave synthesis was applied to prepare nanocrystalline RuO2 dispersion from aqueous RuCl3. RuO2 samples were synthesized at temperature 120, 150, 200, 220 and 250 °C in closed vessel. Reaction time was 5 min. Capacitive properties of RuO2 was investigated by cyclic voltammetry and electrochemical impedance spectroscopy in 1 M H2SO4 and standard three-electrode cell, with ink-type working electrode on glassy carbon substrate. The specific capacitance of 320, 550, 750, 750 F/g was obtained for samples synthesized at temperature 150, 200, 220 and 250 °C respectively, cyclic voltammetry curves are shown in (Fig.1). The best capacitive performance was obtained for sample synthesized at temperature of 200 °C, specific capacitance of 750 F/g which negligibly depend on sweep rate in 5–500 mV/s range. RuO2 dispersion was subjected to dynamic light scattering in order to analyze the synthesized particles, whereas structural and morphological properties of the solid phase are investigated by AFM, SEM, EDAX and XRD techniques.The ordered unusual shape of ca. 100 nm native particles, as well as highly-ordered prismatic agglomerate sheets are observed for sample synthesized at temperature 200 °C .These findings are quite unusual for this kind of material consisted of rather large particles [1], and makes it excellent candidate for both low and high power applicationsJune 07-11, 2015, Pravets, Bulgari

Kompozitni materijal hidratisani rutenijum oksid / ugljenik kao elektrohemijski superkondenzator 3. Kapacitivna svojstva kompozita

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

Kompozitni materijal hidratisani rutenijum oksid / ugljenik kao elektrohemijski superkondenzator 2. Kapacitivne osobine ugljeničnog substrata

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

Electrochemical supercapacitors: Operation, components and materials

Supercapacitors are the best choice when there is a need to deliver high power to the consumer or to store energy. Hybrid supercapacitors with their beneficial characteristics can somewhat overcome the basic lack of batteries, that is the low power density, and when supercapacitors are combined with batteries, the current maximum power can be increased and the lifetime extended. The number of research studies on development of new materials and construction technologies for supercapacitors has been increasing steadily in recent years. As a result, production of commercial devices and their applications are constantly growing, with improved product properties. Here we present the current state of development of supercapacitors as highly promising energy storage systems by an overview of operation principles, main components and various electrode materials and electrolytes, as well as description of different modes of production. A special attention was paid to the need of a good match of the active material and electrolytes, in order to achieve high capacity of the device. The electrode/electrolyte phase optimization is the key to maximizing characteristics of a supercapacitor, especially the capacitance. In selecting the materials, requirements of the final application must be considered, such as the specific energy and power, energy and power density, and service life-time. In addition to material selection, design and optimization of the cell configuration provide new opportunities for development of hybrid battery/supercapacitor systems. Demand for such systems will increase in future, when using a battery or a supercapacitor alone will not be able to meet specific needs, such as the energy density, number of charge and discharge cycles or voltage. Finally, equally important as the development of materials and cells, are the electrode production technology and the cell construction, which need to be optimized in order to improve supercapacitor properties

Kompozitni materijal hidratisani rutenijum oksid / ugljenik kao elektrohemijski superkondenzator 1. dobijanje, morfologija i karakterizacija kompozita

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

AC Impedance tracking of glassy carbon activation

Carbon materials, due to their physical and chemical properties, have found wide application in different electrochemical systems. They are often used as substrates for supercapacitors and different types of electrocatalysts. Upon activation, their electrochemical properties are improved. Glassy carbon can be successfully used as a model for studying the process of carbon activation. In this work, the activation of glassy carbon by electrochemical oxidation in sulfuric acid was investigated using cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. Glassy carbon was oxidized during the same time at 5 different potentials. Cyclic voltammetry shows that the higher the potential the larger the increase in double layer capacitance is. Impedance measurements confirmed significant changes in capacitive response of activated glassy carbon in comparison to unoxidized state. AFM examination of treated GC surfaces revealed morphological changes and increase in roughness upon oxidation. If combined, the results of these studies show that the activation of glassy carbon proceeds through three stages: oxidation of active site, growing of graphite oxide layer and mechanical destruction of the surface.Belgrade, Serbia, June 6-10, 2010Related to the published paper in the Proceedings of the Second Regional Symposium on Electrochemistry South-East Europe, [http://cer.ihtm.bg.ac.rs/handle/123456789/3541

AC Impedance tracking of glassy carbon activation

Carbon materials, due to their physical and chemical properties, have found wide application in different electrochemical systems. They are often used as substrates for supercapacitors and different types of electrocatalysts. Upon activation, their electrochemical properties are improved. Glassy carbon can be successfully used as a model for studying the process of carbon activation. In this work, the activation of glassy carbon by electrochemical oxidation in sulfuric acid was investigated using cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy. Glassy carbon was oxidized during the same time at 5 different potentials. Cyclic voltammetry shows that the higher the potential the larger the increase in double layer capacitance is. Impedance measurements confirmed significant changes in capacitive response of activated glassy carbon in comparison to unoxidized state. AFM examination of treated GC surfaces revealed morphological changes and increase in roughness upon oxidation. If combined, the results of these studies show that the activation of glassy carbon proceeds through three stages: oxidation of active site, growing of graphite oxide layer and mechanical destruction of the surface.Belgrade, Serbia, June 6-10, 2010Related to the published paper in the Proceedings of the Second Regional Symposium on Electrochemistry South-East Europe, [http://cer.ihtm.bg.ac.rs/handle/123456789/3541

Titanske anode aktivirane oksidnom prevlakom dobijenom sol-gel postupkom

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