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Phase structure of electrode coatings prepared by different techniques. The data were given from the Rietveld refinement of the X-ray diffraction patterns.
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![Fig. 2. Phase diagram of binary oxide RuO 2 − TiO 2 [26]. The green...](profile/Ruiyong-Chen/publication/234078024/figure/fig2/AS:300039797788680@1448546470612/Phase-diagram-of-binary-oxide-RuO-2-TiO-2-26-The-green-rectangular-region-marks-the_Q320.jpg)
Industrial chlor-alkali electrolysis represents one of the most energy- and resource-intensive
technological applications of electrocatalysis. Improving process efficiency becomes a critical issue
for the sustainable development and for alleviating the energy and environmental crisis. Rational
design in the morphology of RuO2-based anodic electroca...
Contexts in source publication
Context 1
... the different ki- netics of thermal decomposition of various precursors), some salts can be converted to oxide faster than others and this will result in a heterogeneous microstructure with mixed clusters of individual composition rather than solid solution [38]. This could ex- plain the formation of mixed phase for the thermal decomposition prepared commercial Ru 0.3 Ti 0.7 O 2 coatings (Table 2 in Sect. 5) [15]. ...
Context 2
... solid solution phase is the active component for Cl 2 evolution reaction. The dependence of phase composition and crystallite size on the preparation routes is sum- marized in Table 2. The crystal structure parameters and crystallite sizes were refined from the X-ray diffraction patterns by the Rietveld method using the TOPAS software (Bruker AXS). ...
Context 3
... Ru was exclusively observed in the cathodic deposited film through X-ray photoelectron spectroscopy. This undesired cathodic metal deposition (Ru metal is instable under electrolysis conditions) can be inhibited partially by applying higher current densities in the electrodeposition process (Table 2). In this case, the cathodic production of OH − is faster and the deposition of M(OH) n is favored. ...
Context 4
... The heterogeneity in the microstructure is also not favorable for the long-term electrode stability [41]. Single rutile solid solution phase has been achieved for the sol-gel derived RuO 2 −TiO 2 and RuO 2 −SnO 2 coatings ( Table 2). The substitution of Ti by Sn is effective to reduce the crystallite size from about 18 to 5 nm. ...
Context 5
... the sol-gel Ru 0.3 Sn 0.7 O 2 coatings with a Ru loading amount of about 6-8 g m −2 , a decrease in the electrode potential by about 50-90 mV in comparison to that of commercial coatings is obtained (Table 3). The remarkable enhancement in the per- formance of sol-gel Ru 0.3 Sn 0.7 O 2 coatings can be attributed to the extremely small crys- tallite size (5 nm, Table 2). The crystal growth is inhibited in the binary RuO 2 −SnO 2 coating due to the large difference in the lattice parameters between the RuO 2 (a = 4.4994 Å, c = 3.1071 Å, V = 62.9 Å 3 ) and SnO 2 (a = 4.7382 Å, c = 3.1871 Å, V = 71.6 ...
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Anodes containing ruthenium, titanium, and tin oxides supported on metallic Ti were prepared by thermal decomposition of precursor salts in order to investigate the effect that changing the solvent (from HCl/H2O to isopropanol) would have on the real composition of the mixed oxide electrodes. The precursor solutions and their mixtures were analyzed...
Reduction of toxic dissolved fluoride and CaF2 nanoparticle pollution is a critical environmental problem for the semiconductor industry. In this study, suspended matter and fluoride are simultaneously eliminated by combining coagulation and electroflotation. The EF cell was equipped with DSA titanium coated with ruthenium oxide (Ti/RuO2) as anode...
Citations
... 19 Good mixing of the metal alloys, and preferably formation of an oxide solid solution, results in optimal performance. 20 Although DSAs tend to have excellent stability, cracks that form in the catalyst coating from the thermal decomposition preparation method can result in passivation of the underlying substrate. For example, the degradation mechanism of an IrO 2 /RuO 2 /SiO 2 DSA during the OER in sulfuric acid electrolyte was found to be dissolution of the active components followed by oxidation of the underlying Ti substrate to insulating TiO 2 which resulted in a sharp deactivation. ...
RuO 2 is a highly active electrocatalyst for the oxygen evolution reaction (OER) but is unstable in acidic environments. We investigated the encapsulation of RuO 2 nanoparticles with semipermeable, nanoscopic silicon oxide (SiO x ) overlayers as a strategy to improve their stability. SiO x encapsulated RuO 2 (SiO x |RuO 2 ) electrodes were prepared by drop-casting RuO 2 nanoparticles onto glassy carbon substrates followed by deposition of SiO x overlayers of varying thickness by a room-temperature photochemical deposition process. The best-performing SiO x |RuO 2 electrodes consisted of 2-3 nm thick SiO x overlayers on top of RuO 2 particles and 3-7 nm thick SiO x on the glassy carbon substrate. Such electrodes exhibited lower overpotentials relative to bare RuO 2 due to an improved electrochemically active surface area while also demonstrating an ability to retain OER activity over time, especially at higher overpotentials. Surprisingly, it was found that the SiO x coating was unable to prevent Ru dissolution, which was found to be proportional to the charge passed and independent of the presence or thickness of the SiO x coating. Thus, other possible explanations for the improved current retention of SiO x |RuO 2 electrodes are discussed, including the influences of the overlayer on bubble dynamics and the stability of the underlying glassy carbon substrate.
... The electrochemical oxidation of the chloride ion Clin aqueous solutions is studied actively, mainly, in connection with wit the Cl 2 and NaOH industrial production by way of electrolysis of NaCl solution. The electrolysis products are both molecular chlorine Cl 2 dissolved in the solution and in the gas phase above it [1,2], and compounds with intermediate oxidation degrees, mainly, trichloride-anion [3]: ...
... 2а-2с [4]) also are under consideration. In these diagrams, certain components of the system are excluded from the consideration, namely: (1) is disregarded; (2) and are excluded, that is, only HClO 2 , , HClO, ClO -, Cl 2 , and Clin solution are under consideration; (3) only dissolved components HClO, ClO -, Cl 2 , and Clare taking into account. In each variant, components the allowance is made for are assumed being in thermodynamical equilibrium with one another at given values of the solution potential Е and рН. ...
... The chloride ion Clelectrochemical oxidation in aqueous solutions was studied actively, first, in connection with the Cl 2 and NaOH industrial production by the NaCl solution electrolysis. In the electrolysis, the anodic process produced molecular chlorine as both a dissolved Cl 2 and that in gas phase above the solution, [1,2]: (1) To simplify the writing, all components of the system situated in liquid phase (in particular, Cland Cl 2 in equation (1)), as well as their concentration and activities are always given without subscript "aq", whereas those in gas phase, with a subscript "gas". ...
... The chloride ion Clelectrochemical oxidation in aqueous solutions was studied actively, first, in connection with the Cl 2 and NaOH industrial production by the NaCl solution electrolysis. In the electrolysis, the anodic process produced molecular chlorine as both a dissolved Cl 2 and that in gas phase above the solution, [1,2]: (1) To simplify the writing, all components of the system situated in liquid phase (in particular, Cland Cl 2 in equation (1)), as well as their concentration and activities are always given without subscript "aq", whereas those in gas phase, with a subscript "gas". ...
Theoretical analysis of changes in the composition of the system in the course of electrolysis of acidic aqueous chloride solution +
P. A. Zader1,*, D. V. Konev1,2, J. Gun3, O. Lev3, M. A. Vorotyntsev1,*
1 Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences, Moscow, Russia
2 Institute for Problems of Chemical Physics of the Russian Academy of Sciences, Chernogolovka, Russia
3 Hebrew University of Jerusalem, Jerusalem, Israel
*e-mails: paul.zadyor@gmail.com (P. A. Zader) , mivo2010@yandex.com (M. A. Vorotyntsev)
Resume:
Variation of the indicator electrode potential under zero current condition, E, and of the (quasi)equilibrium composition of the aqueous solution (which initially contains 0.5 M chloride anion) in the anode chamber of a model electrolytic cell were calculated, provided that the pH of the solution is kept constant (pH 0) and that the same total number of Cl atoms in all its compounds (including the gas phase above it) is maintained. Theoretical analysis has been carried out for five different hypotheses regarding the possible depth of oxidative electrolysis and the nature of the processes taking place: (a) no formation of chlorine compounds with oxidation states above +1, i.e. the electrolysis leads only to formation of molecular chlorine Cl2 in the solute state and inside gas space over the solution Cl2gas, trichloride anion Cl3- as well as solute HClO and ClO- (besides the retaining amount of Cl-); (b) in addition to the compounds indicated for case (a), chlorine compounds are formed in solution in the +3 oxidation state, i.e. HClO2 and ClO2-; (c) besides the compounds listed for case (b), chlorine compounds are formed in the +4 oxidation state, i.e. solute ClO2 and ClО2gas in the gas phase; (d) the process proceeds with formation of both the chlorate ion (ClO3-) and the chlorine compounds of lower oxidation states in solution and in gas phase indicated above for case (c) (Cl-, Cl3-, Cl2, Cl2gas, HClO, ClO-, HClO2, ClO2-, ClO2 и ClO2gas); (e) in addition to the components indicated for variant (d), perchlorate anion (ClO4-) can also be formed. All electrochemical and chemical reactions with participation of chlorine-containing particles which are taken into account within the framework of each of the options (a), (b), (c), (d) or (e), are assumed to be in (quasi)equilibrium state. Predictions for all these 5 hypotheses on the relationship between the redox charge of the system, Q (or the average oxidation state of chlorine atoms, x), and the indicator electrode potential, E, as well as on the dependence of the composition of the system (concentrations of all compounds) on either x or E have been derived. Approaches for experimental determination of the variant of evolution of the composition of Cl-containing anolyte in the course of electrolysis has been proposed.
Keywords: chloride anion electrooxidation, equilibrium composition, trichloride anion, molecular chlorine and chlorine dioxide in solute and gaseous forms, HClO, HClO2, anions ClO-, ClO2-, ClO3- and ClO4-, quasi-equilibrium composition
+ The article has been prepared for the special journal’s issue, devoted to memory of the great electrochemist Oleg Petrii.
... NaCl aqueous solution was served as the anolyte, Na 2 CO 3 aqueous solution was served as the catholyte [25]. Yttria-coated titanium (Ti) mesh was used as the anode [26,27], self-made GDE was used as the cathode. During the electrolysis process, CO 2 is reduced to CO on the GDE [28], with CO 3 2− generated accompanying with CO formation. ...
A novel gas diffusion electrode (GDE) electrolyzer has been constructed to convert CO2 into CO, with chlorine (Cl2) and sodium carbonate (Na2CO3) produced as the by-products. Using this method, the product value yielded from CO2 electrolysis can be increased substantially. In contrast to the conventional GDE electrolyzer, we use a cation-exchange membrane as the diaphragm to separate the cathode from the anode compartment, and use NaCl aqueous solution as the anolyte. During the electrolysis process, CO2 is reduced to CO on the cathode, with CO3²⁻ generated accompanied with CO formation. On the anode, Cl⁻ is oxidized to Cl2. Na⁺ in the anode chamber transfers through the cation-exchange membrane, and migrates into the catholyte. Thus, Na2CO3 can be obtained owing to the co-existing of Na⁺ and CO3²⁻ in the catholyte. Using this method, CO3²⁻ penetrating through the anion-membrane can be avoided. This problem has been considered as the crucial obstacle that impedes the practical utilization of the conventional GDE electrolyzer. Our designed GDE electrolyzer has a promising application perspective in the phosgene chemical industry.
... In their pioneering work, Fischer et al. synthesized rubidium oxoruthenate (Rb2RuO4) from rubidium peroxide and ruthenium dioxide and also calculated its magnetic properties [11]. The trioxide of rubidium and ruthenium (RbRuO3) decomposes to Rb2RuO4 and RuO2, where RuO2 crystallizes with tetragonal rutile structure (P42/mmm) [12], whereas Rb2RuO4 crystallizes with an orthorhombic structure (Pnma) [11]. These products, under certain physical-chemical circumstances such as thermal treatment, combine to produce the perovskite RbRuO3 in Pm3 ̅ m space-symmetry group [4,13]. ...
Trioxides of rubidium, strontium, and ruthenium belong to the family of alkali and alkaline earth ruthenates. SrRuO3 crystallizes in various symmetry classes—orthorhombic, tetragonal, or cubic—whereas RbRuO3 is perovskite (cubic) structured and crystallizes only in the cubic space group Pm3¯¯¯m(No. 221). In this study, we investigated the structural stability as well as the electronic and magnetic properties of two cubic perovskites SrRuO3 and RbRuO3. We established the corresponding lattice parameters, magnetic moments, density of states (DOS), and band structures using ab‑initio density‑functional theory (DFT). Both compounds exhibited a metallic ferromagnetic ground state with lattice parameter values between 3.83 and 3.96 Å; RbRuO3 had magnetic moments between 0.29 and 0.34 µBwhereas SrRuO3 had magnetic moments between 1.33 and 1.66 µB. This study paves way for further RbRuO3 research.
... adsorbed on the anode surface, electro-generated) contrast against the aforementioned aqueous chlorine species, very stable in solution. In connection with this hypothesis, tremendous efforts have been carried out to synthesize numerous RuO 2 -based anodes, by stabilizing the Ru(IV) cations within its crystal lattice using TiO 2 , ZrO 2 , SnO 2 , Ta 2 O 5 , Nb 2 O 5 [11,[15][16][17][18]. In addition, activity, stability, selectivity and material cost are remarkably improved. ...
It is accepted that the mechanism of electro-generated active chlorine (i.e. chloride oxidation on DSAs) involves water oxidation and hydroxyl radical co-electrosorption to initially form HOCl ads on the anode surface in a single pathway, and subsequent production of Cl 2 and OCl − ions. The present study comprehensively evaluates the chloride oxidation on Ti/RuO 2-IrO 2 in solutions containing different NaCl concentrations and pH values. Differential Electrochemical Mass Spectroscopy (DEMS) is used to account for the in-situ surface reactions simultaneously occurring during chloride and water oxidations. It is found that HOCl does not lead the chlorine mechanism since OCl ⦁ is detected in considerably larger amounts under some experimental conditions, and its onset overpotential is~150 mV more negative than HOCl appearance at 0.2 mol L −1 NaCl. Additionally, the mass signals of OCl ⦁ and HOCl are virtually similar at pH = 2 and slightly different at pH = 10, where these species should not respectively exist according to thermodynamic information. Under this premise, an extension of the reaction mechanism is proposed to consider an independent pathway producing adsorbed hypochlorite radical (OCl • ads) for electro-generated active chlorine, which could be the preferential one since RuO 2 and IrO 2 belong to the category of "active" anodes towards the Oxygen Evolution Reaction (OER), thus allowing the formation of the so-called higher oxide MO x (⦁ O) ads (chemisorbed oxygen). Although the mechanisms involving the productions of HOCl ads and OCl • ads can simultaneously occur on two type of non-identified active sites, promoting the generation of both MO x (⦁ OH) ads and MO x (⦁ O) ads species, both strongly depend on surface pH.
... This observation suggests that TiO 2 layer could orient the tetragonal crystalline structure RuO 2 growth, mainly favored for their similar lattice parameters. In addition, the ionic radii of Ru 4+ , Ti 4+ are 62.0 × 10 −12 and 60.5 × 10 -12 m, respectively [25]. Maximum difference each other is 2.4 %, smaller than the Hume-Rothery limit for successful substitution, i.e., 15 % [26]. ...
A photo-assisted electrochemical process is herein evaluated with the aim of improving and accelerating the degradation and mineralization of Ciprofloxacin (CIP) in aqueous media, in comparison with single electrochemical or photochemical methods. Active chlorine species are initially electro-generated on a synthesized (Pechini method) Ti/TiO2-RuO2 DSA, and subsequently fragmented homolitically using UVC irradiation under very low fluency rate (3300 µW cm⁻², λ = 254 nm) to produce radicals with higher oxidation potentials compared to the original active chlorine. A faster CIP degradation (5 min) and higher mineralization is obtained in the coupled system against the individual techniques. Variations of pH and current density in the UV-assisted electrochemical process reveal that a similar degradation rate is obtained during 60 min for pH 6 and 9 due to the co-existence of HOCl and OCl- species in this range of pH, leading to the possible production of highly reactive radicals (e.g.HOaq•, Claq•, Oaq-•) after chlorine species fragmentation. The highest total organic Carbon (TOC) removal was obtained at pH = 6 (70% in 60 min), where the highest HOCl concentration is observed, thus, enhancing the HOaq• production. The contaminant degradation and mineralization strongly depend on the radicals formed from the irradiation of chlorine species, which on its turn rely on the redox couples formed as a function of pH: 3 (HOCl + Cl2), 6 and 9 (HOCl + OCl-). Mechanisms are proposed for these homolysis reactions, while the degradation pathway of CIP is rationalized using HPLC analyses during 60 min of electrolysis.
... Graphite is a traditional and widely used anode electrode in chlorine alkali industry due to its abundance in resources and low price. 3,4 However, the overpotential of Cl À ions is high, which increases the bath voltage during the electrolytic process. Besides, anode corrosion consumption of graphite not only reduces its useful life span but also blocks the membrane. ...
High-performance electrodes can solve problems of high voltage and large electricity consumption existing in chlor-alkali industry. A Ti/Al laminate composite (named as Ti/Al-LC) with three-layered structure (Ti/Al 3 Ti/Ti) is prepared as a new type of anode electrode for chlor-alkali electrolysis. Scanning electron microscope observation shows that the Ti/Al-LC is composited of a thicker inner layer with thickness about 700 µm and two thinner outer layers with thickness about 300 µm. From the X-ray diffraction pattern, it is known that the outer layers consisted of α-Ti and β-Ti phases, while the inner layer consisted of Al 3 Ti intermetallic phase. A saturated sodium chloride (NaCl) solution at 70°C is purposely chosen as the corrosion electrolyte to analyze the corrosion behavior of Ti/Al-LC as anode electrode for chlor-alkali electrolysis. Electrochemical tests, including potentiodynamic polarization and electrochemical impedance spectroscopy measurements, on a three-electrode system indicate that the Ti/Al-LC has a low corrosion rate with corrosion current density of 1.94 µA cm ⁻² and stable surface passive film in saturated NaCl solution at 70°C.
... In Europe, the installed capacity is 9.6 Mtonne chlorine, 59 of which 80% is produced using membrane or diaphragm cells. The reaction at the IrO x and RuO x -coated titanium anodes is: 60 [ ] ...
The features of the plane parallel geometry are reviewed since this cell geometry occupies a prominent position, both in the
laboratory and in industry. The simple parallel plate can be enhanced by inclusion of porous, 3D electrodes, structured surfaces and
bipolar electrical connections, with adequate attention to the reaction environment. Unit cells are often arranged in a modular, filterpress
format. Scale-up is achieved by increasing the size of each electrode, the number of electrodes in a stack or the number of
stacks in a system. The use of turbulence promoters in the flow channel, textured (including nanostructured) and porous electrodes
as well as cell division by an ion exchange membrane can considerably widen the scope of the plane parallel geometry. Features of
plane parallel cell designs are illustrated by selected examples from our laboratories and industry, including a fuel cell, an
electrosynthesis cell and hybrid redox flow cells for energy storage. Recent trends include the development of microflow cells for
electrosynthesis, 3D printing of fast prototype cells and a range of computational models to simulate reaction environment and
rationalise performance. Future research needs are highlighted.
© 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. This is an open access
article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/
by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/
1945-7111/ab64ba]
... Such materials can be electrodeposited both on the cathode and on the anode using aqueous solutions, non-aqueous solvents, ionic melts and ionic liquids. It should be noted that electrocatalytic oxide/hydroxide layers formed via cathodic and anodic deposition were earlier characterized in a number of review and original papers [3][4][5][6][7][8][9]; these coatings will not be considered in the present work. Also, polymer and semiconductor films are not described here. ...
Among different methods of fabrication of electrocatalytic coatings, the electrodeposition seems to be the most convenient and widely used. The electrodeposition is an available, inexpensive, versatile, simple and fast technique which allows synthesizing materials with controlled composition, structure, surface morphology and electrocatalytic activity. This review reports recent trends, promising directions and novel approaches concerning cathodic electrodeposition and characterization of electrocatalytic coatings. A special attention is paid to the electrocatalysts based on electrodeposited nickel, iron, cobalt, copper, chromium, noble metals, their alloys and composites. The application of non-stationary current regimes (pulse current and linear potential sweep) as well as new type of plating baths (room-temperature ionic liquids and deep eutectic solvents) is highlighted. The influence of alloying and after-treatment (dealloying, selective anodic dissolution, etc.) on the electrocatalytic properties of electrodeposits is considered. Favorable influence of the formation of nanostructures upon the electrocatalytic performance of electrodeposited materials is shown. Potential ways for improving the electrocatalytic characteristics of electrodeposited coatings are described.
