Synthesis and characterization of structurally ordered interactive electrocatalytic composites based on metal oxides and platinum

Ispitivana su svojstva titan(IV)-oksida i njegove karakteristike kao mogućeg interaktivnog i stabilnog nosača za RuO2 i Pt kao elektrokatalizatora u reakcijama od značaja za industrijsku elektrohemiju i alternativne izvore energije. Analizirano je i razmatrano kako u slučaju kompozita RuO2/TiO2 i Pt/TiO2, sintetizovanih na takav način da se dobijaju njihove uređene strukture, TiO2 služi kao stabilišuće i interaktivno jezgro, a RuO2, odnosno Pt, kao elektrokatalitički aktivna komponenta. Kompoziti RuO2/TiO2 i Pt/TiO2 su sintetizovani različitim hidrotermalnim metodama, koje uključuju temperaturno kontrolisan prelaz aerosolova i hidrosolova u čvrstu fazu. Kod kompozita RuO2/TiO2 se ispitivao uticaj temperature u pirolitičkom reaktoru na morfologiju dobijenog kompozita RuO2/TiO2 i stabilnost anoda koje su dobijene nanošenjem ovako dobijenog kompozita na Ti podlogu. Svojstva dobijenih kompozita analizirana su u zavisnosti od toga da li su sve faze sintetizovane u jednom koraku (in-situ) ili je faza nosača TiO2 sintetizovana prethodno (ex-situ). Strukturno-morfološka svojstva dobijenih materijala ispitivana su mikroskopskim tehnikama (SEM, TEM), analizom interakcije materijala sa elektromagnetnim zračenjem (FTIR, XRD, DLS, ramanska spektroskopija) i termogravimetrijskom analizom. Elektrohemijske karakteristike ispitivane su analizom nefaradejskog odziva i elektrokatalitičke aktivnosti i stabilnosti u reakcijama izdvajanja hlora i kiseonika (RuO2/TiO2), odnosno redukcije kiseonika i izdvajanja vodonika (Pt/TiO2). Nađeno je da se svi kompoziti dobijaju u obliku sferoidnih čestica/aglomerata, bez obzira na postupak dobijanja. Uređenost i ravnomernost strukture zavise od primenjenog postupka pripreme, kao i temperature prelaza u čvrstu fazu. Elektrohemijskim karakteristikama RuO2/TiO2 pogoduje niža temperatura pirolitičke sinteze, iako je utvrđeno da u tom slučaju izostaje potpuna konverzija prekursora rutenijuma u odgovarajući oksid. RuO2/TiO2 dobijen na nižoj temperaturi se pokazao stabilnijim, sa boljim kapacitivnim karakteristikama, usled karakteristične raspodele komponenti i faza kroz zapreminu matičnih sferoidnih strukturnih oblika kompozita. Za nominalno isti sastav RuO2/TiO2 dobijen na nižoj i višoj temperaturi, razmatrano je kako elektrohemijske karakteristike zavise od mikroskopske raspodele oksidnih komponenti kroz sferične aglomerate. Takođe, ovi nalazi diskutovani su uzimajući u obzir i kristalno stanje TiO2 u formi anatasa, koji pretežno čini jezgro ovih aglomerata. Kod kompozita Pt/TiO2 se ispitivao uticaj temperature sinteze i tipa sinteze na morfološka svojstva dobijenog kompozita i njegovu elektrokatalitičku aktivnost. Svi dobijeni kompoziti su bili sfernog oblika, nezavisno od primenjenih uslova sinteze. U ex-situ pristupu USP sintezi se dobijaju pravilna sferna jezgra čija je površina prekrivena ljuskom u vidu nanometarskih platinskih čestica, dok se in-situ pristupom dobija smeša većih šupljih sfera i manjih čvrstih sfera. Najbolja elektrokatalitička svojstva pokazuje kompozit sintetizovan ex-situ pristupom na umerenoj temperaturi.Properties and characteristics of titanium(IV) oxide, as posible interactive and stable support for RuO2 and Pt electrocatalysts, are studied. RuO2 and Pt are important electrocatalytic materials, often used in industrial electrochemistry and alternative power sources. It was found that in Pt/TiO2 and RuO2/TiO2 composites synthesized in a way which enables highly ordered structures TiO2 acts like a stabilising and interactive core, while Pt and RuO2 are electrocatalyticaly active components encapsulating the core. As supporting component in both Pt/TiO2 and RuO2/TiO2 composites, TiO2 synthesis and its characterisation is performed separately. RuO2/TiO2 and Pt/TiO2 composites are synthesiezed using varouis hydrothermal approches consisting of temperature-controled conversion of aerosols and hydrosols to the solid phase. In the case of RuO2/TiO2 composite, influence of synthesis temperature on the morphology of the obtained composites was studied. Influence of the synthesis temperature on the stability of activated Ti anodes coated by obtained composites was examined as well. Dependance of the properties of the obtained composites on the applied synthesis approach was investigated. In-situ approach as one-step synthesis is applied along with the ex-situ approach, which implies that at least supporting component, TiO2, has been prepared prior to the composite synthesis. Strucutral and morphological properties of the obtained materials were tested using SEM, TEM, FTIR, XRD, DLS, Raman and TGA techniques. Electrochemical characterization involved the analysis of non-Faradaic response and electrocatalytic activity and stability in chlorine and oxygen evolution reactions (RuO2/TiO2), as well as oxygen reduction and hydrogen evolution reactions (Pt/TiO2). It was found that all synthesized composites had spherical shape, independently of the synthesis method. Structure arrangement and uniformity depend on the applied approach, as well as on the synthesis temperature. Although conversion of ruthenium precursor to coresponding oxide was not complete at lower synthesis temperature, this temperature is beneficial for electrochemical characteristics of the RuO2/TiO2 composite. Namely, RuO2/TiO2 composite synthesiezed at lower temperature had better stability and capacitive characteristics. Influence of the microscopic distribution of the oxide components throughout the spherical agglomerates on the electrochemical characteristics of the RuO2/TiO2 composites synthesized at two different temperatures, with same nominal composition, was investigated. In addition, the disscusion takes into account the influence of the anatase TiO2 that cores are primary consisted of. Influence of the synthesis temperature and method on the morphological properties and electrocatalytic activity of the obtained Pt/TiO2 composites were examined. All of the prepared composites were of spherical shape, independently of the applied conditions. Regular spherical cores covered by a shell of nanometric platinum particles were obtained by ex-situ approach, whereas in-situ aproach resulted in mixture of huge hollow speheres and smaller all-solid spheres. The most promising electocatalytical properties were obtained by ex-situ USP method at moderate temperatures

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

Poboljšanje oksidacije etanola na Pd elektrohemijski nataloženom preko Sb2O3

Electrodeposited Pd and Sb-Pd catalysts were tested for the ethanol oxidation reaction by cyclic voltammetry and chronoamperometry. Palladium-antimony deposit was synthesized on a glassy carbon substrate by a two-step process, comprising deposition of Sb followed by deposition of Pd. The Sb-Pd electrocatalyst with the Sn:Pd atomic ratio 0.2:0.8 was obtained. Compared with pure Pd, the incorporation of Sb results in the increase of activity and stability of bimetallic catalyst for the electrocatalytic ethanol oxidation reaction. Besides upon the end of the current-time transient, the investigated Sb-Pd catalyst was subjected to the potential cycling showing the ability to recover activity loss implying the surface composition stability. The enhanced performance of Sb-Pd is mainly ascribed to the bifunctional mechanism and electronic effect.Elektrohemijski nataloženi Pd i Sb-Pd katalizatori su ispitivani u reakciji oksidacije etanola cikličnom voltametrijom i hronoampeometrijskom metodom

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

Poster presentation: The pseudo-capacitance of hydrous RuO2 accompanied by mass changes

Pseudocapacitance reaction of ruthenium oxide was investigated by cyclic voltammetry (CV) measurements combined with electrochemical quartz-crystal nanobalance. RuO2 was synthesized by one-pot microwave assisted hydrothermal method. CV measurements were conducted in H2SO4 and Na2SO4 solutions. The ruthenium oxide electrode as a working electrode was prepared by drop casting the water suspension of RuO2 on Au covered quartz electrode. Beside influence of different electrolyte, the effect of thermal treatment of RuO2 was also investigated since pseudocapacitive behaviour of RuO2 strongly depends on its hydrous form. The obtained results were compared to those of commercial RuO2. The results indicate that during the redox reaction of RuO2, various types of charge occur simultaneously. The mass loss or mass gain depends on the specific potential applied and the electrolyte employed.Poster presentation at Fifth international symposium on corrosion and materials protection, environmental protection and protection against fire proceedings, Proceedings, 26-29. septembar 2023. godine, Bar.Conference paper: [https://cer.ihtm.bg.ac.rs/handle/123456789/7138

A novel approach for the study of the kinetics of sol-gel synthesis of titanium dioxide nanoparticles as catalyst support

Owing to a wide range of application in kinetics (photocatalysis, electrocatalysis, etc.), it is of high importance to define in details corelation between structure and synthesis of TiO2 particles. The aim is to elucidate the kinetics of TiO2 solid phase formation by sol-gel approach as newly-structured suitable carrier of batteries/fuel cells electrocatalytic materials. TiO2 nanoparticles were synthesized from TiCl3 precursor under different conditions (concentration, pH) in an aqueous medium. Formation of a new solid phase was continuously monitored by a dynamic conductometric measurements induced by high frequency impedance sinusoidal voltage perturbations of a conductometric cell. The particle size distributions of the obtained TiO2 sols were characterized by the dynamic light scattering method, while the microstructure data were obtained by the scanning electron microscopy. The typical change of high frequency impedance during TiO2 synthesis is presented in Figure 1. It was found that the process proceeds through at least five phases (I–V, Figure 1, seen as high frequency impedance decrease) of different rates and durability, which depend on synthesis conditions

Impedansni odgovor aluminijuma sa zaštitnom prevlakom oksida cerijuma tokom izlaganja hloridnoj korozionoj sredini

Electrochemical impedance characteristics of bare Al and Al with CeO2 coating prepared sol-gel procedure from the ceria sol are investigated. The corrosion behavior is monitored during the exposure to 3 wt. % NaCl aqueous solution. Experimental data are fitted to various equivalent electrical circuits with special attention to inductive features. Equivalent electrical circuits involving inductivity represent impedance response equally well as the ones without inductivity, although the parameter values gained from the former correspond better to the proposed model of physicochemical changes during corrosion of investigated samples.Korozione karakteristike aluminijuma i aluminijuma na koji je naneta prevlaka oksida cerijuma sol-gel postupkom ispitivane su primenom spektroskopije elektrohemijske impedancije tokom izlaganja u vodenom rastvoru 3 mas. % NaCl. Dobijeni podaci analizirani su ekvivalentnim električnim kolima različite konfiguracije uz posebnu diskusiju koja se odnosi na pojavu induktivnog ponašanja. Ekvivalentna kola sa induktivnim elementom i bez njega podjednako dobro opisuju impedansne odgovore, mada vrednosti parametara kola u kojima je uključena induktivnost više odgovaraju predloženom modelu fizičko-hemijskih promena tokom procesa korozije ispitivanih sistema

TiO2 From Colloidal Dispersion as Support in Pt/TiO2 Nanocomposite for Electrochemical Applications

TiO2 powder was synthesized by a forced hydrolysis process and used for the synthesis of Pt/TiO2 composite that is to be foreseen as an advanced electrode material. Pt was incorporated into the synthesized TiO2 from a Pt colloidal dispersion as a precursor prepared by a microwave-assisted polyol process. Physicochemical properties of TiO2 and TiO2-supported Pt were investigated by scanning electron microscopy, dynamic light scattering and X-ray spectroscopy and diffraction techniques. The properties of Pt/TiO2 composite are correlated to the basic voltammetric response of its thin-layer form. It was found that subsequent thermal treatment of synthesized TiO2, which caused crystallization into mainly rutile phase, is required for appropriate Pt incorporation. Although being appropriately loaded by Pt, and the voltammetric response is typical for Pt-based material, the voltammetry of Pt/TiO2 corresponded to much lower loadings. The possibility for Pt particles to be trapped inside TiO2 agglomerates is indicated. The catalyst usage from the synthesized Pt/TiO2 was found quite moderate due to this trapping. This work is licensed under a Creative Commons Attribution 4.0 International License

Copper Electrodeposition onto Palladium from a Deep Eutectic System Based on Choline Chloride

Recently, there has been an increasing interest in developing nonaqueous electrolytes which have been widely employed as an alternative media for a range of metals and metal alloys electrodepositions. A promising and new class of electrolytes among ionic liquids (Ils) are deep eutectic solvents (DESs)1 . The purpose of the copper deposition study from DESs is the application of copper coating and copper alloys in both, industry and fundamental research. In this work, the electrochemical deposition of copper onto palladium working substrate from ChCl/EG (1:2 ratio) DES electrolyte at 50°C was investigated. Additionally, the Cu(II) electroreduction process was studied by potentiodynamic measurements, cyclic voltammetry, chronoamperometry, in the electrolytes with different concentrations of Cu(II) ions ranging from 0.1 M to 0.5 M. The cyclic voltammetry results indicated that the bulk deposition of Cu(II) begins to occur at around –0.080 V vs. Cu. It was found that copper deposition onto the Pd cathode from ChCl:EG electrolyte under potentiostatic conditions is achievable. Data collected from X-ray diffraction (XRD) analysis proved that the cathodic deposits are composed of Cu and CuPd intermetallic. CuPd alloys with different Pd-Cu ratios were prepared by constant potential of –0.100 V vs. Cu from ChCl/EG containing 0.1 M and 0.5 M Cu(II). It is worth noting that the Xray data indicated that the composition of the produced Pd-Cu films could be varied by changing the concentration of Cu(II) ions in the electrolyte or changing the deposition mode

Supercapacitors based on graphene/pseudocapacitive materials

Composites of graphene and SnO2 were successfully prepared by a single step simultaneous synthesis of SnO2 and reduction of graphene oxide (GO). Three different compositions of precursor solution resulted in different composite materials containing graphene and SnO2. The reaction was realized by microwave-assisted hydrothermal synthesis. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) gave insight into the morphology and composition of the obtained materials. Good capacitive/pseudocapacitive properties of the obtained material suitable for supercapacitor application were registered by cyclic voltammetry, from where specific capacitance values up to 93 F g(-1) were determined