Reaction pathways and mechanisms of the electrochemical degradation of phenol on different electrodes

Laboratory experiments were carried out on the kinetics and pathways of the electrochemical (EC) degradation of phenol at three different types of anodes, Ti/SnO2-Sb, Ti/RuO2, and Pt. Although phenol was oxidised by all of the anodes at a current density of 20 mA/cm2 or a cell voltage of 4.6 V, there was a considerable difference between the three anode types in the effectiveness and performance of EC organic degradation. Phenol was readily mineralized at the Ti/SnO2-Sb anode, but its degradation was much slower at the Ti/RuO2 and Pt anodes. The analytical results of high-performance liquid chromatography (HPLC) and gas chromatography coupled with mass spectrometry (GC/MS) indicated that the intermediate products of EC phenol degradation, including benzoquinone and organic acids, were subsequently oxidised rapidly by the Ti/SnO2-Sb anode, but accumulated in the cells of Ti/RuO2 and Pt. There was also a formation of dark-coloured polymeric compounds and precipitates in the solutions electrolyzed by the Ti/RuO2 and Pt anodes, which was not observed for the Ti/SnO 2-Sb cells. It is argued that anodic property not only affects the reaction kinetics of various steps of EC organic oxidation, but also alters the pathway of phenol electrolysis. Favourable surface treatment, such as the SnO2-Sb coating, provides the anode with an apparent catalytic function for rapid organic oxidation that is probably brought about by hydroxyl radicals generated from anodic water electrolysis. © 2005 Elsevier Ltd. All rights reserved.postprin

New solutions in the ferrates(VI) process with the use of SnО₂–modified electrodes

Изучены особенности образования ферратов(VI) из соединений Fe(III) в растворах с различным ионным составом на инертных SnО₂-электродах, легированных Ru, Pt, Pd и Sb. Установлено, что изменением природы и содержания легирующего металла можно целенаправленно регулировать электро-каталитические свойства анодов, в частности величину перенапряжения выделения О₂. Показана принципиальная возможность электрохимического окисления на поверхности электрода и химического окисления в объеме раствора частиц Fe(ОН)₃ и Fe(ОН)₄. Разработаны рекомендации для синтеза ферратов(VI) с использованием анодов, обеспечивающих длительный режим работы без ухудшения их эксплуатационных характеристик.Disadvantages of traditional synthesis methods of ferrates (VI) - promising green oxidants - stimulate the search of new technological solutions which meet the requirements of modern production. The purpose of this work was to study the ferrates (VI) formation from Fe (III) compounds in solutions with different pH on inert SnО₂ electrodes doped with Pt, Ru, Pd, and Sb. The influence of the nature and the content of the alloying metal on the electrocatalytic properties of the electrode was studied by the stationary voltammetry method, as well as by determining the current yields of hypochlorite and sodium chlorate during the electrolysis of a slightly alkaline NaCl solution. Coatings based on SnО₂, doped with palladium and platinum, show maximal electrocatalytic activity according to ClO – synthesis. It has been established that the oxygen evolution overvoltage on the electrodes with comparable dopant concentrations increases in the Ru-Pd-Pt-Sb series. It has been shown that for effective synthesis of ferrates (VI), flat Ti anodes of a large area with an electroactive layer based on SnО₂-Sb2О₃ should be used. It is noted that electrochemical oxidation of Fe (III) in Fe (VI) is more energetically favorable on these electrodes than О₂ evolution, which opens up new possibilities for these processes in ferrate (VI) synthesis technology. We have shown the principal possibility of increasing the productivity of the Fe (VI) process due to the direct interaction of the Fe(ОН)₃ and Fe(ОН)₄− particles in the solution volume with ClO− anions generated on an inert electrode when Сl− anions are preliminarily added to the system. Technological solutions have been proposed to increase the life of inert electrodes when 5-10% TiO2 is introduced into the SnО₂ matrix, providing a long-term operating mode without degradation of their performance characteristics

Optimization of Ti/Ta2O5–SnO2 electrodes and reaction parameters for electrocatalytic oxidation of methylene blue

Among existing water treatment methods for organic-containing wastewaters, advanced oxidation process, particularly electrocatalytic oxidation, is a technique allowing to reach high degradation and mineralization efficiencies. Electrodes tested for use in electrocatalytic oxidation processes contain either expensive or platinum/group metals such as Pt-, Ru-, Ir-, Pd-, or boron-doped diamond and Sb and Pb compounds which are toxic for the environment. Thereby, there is a need for environmentally friendly and less expensive electrodes. The objectives of this research were to optimize annealing temperature of Ti/Ta2O5–SnO2 electrodes, establish the working media for organic compound oxidation processes as well as check degradation, mineralization and current efficiencies for methylene blue dye oxidation. Decolorisation efficiency of 95 % was achieved in 2 h at pH = 6.5. Neutral media showed also higher efficiency towards COD decrease which was equal to 85 % after 2 h of electrolysis. The lowest energy consumption of 7.7 kWh m−3 required for 100 % decolorisation was observed for the electrodes annealed at 550 °C at pH = 2. The highest current efficiency of 10.1 % attributed to 80 % of COD reduction was obtained for the electrode annealed at 550 °C at pH = 6.5. The optimization data allow further extrapolating of electrocatalytic oxidation process on Ti/Ta2O5–SnO2 electrodes to pilot scale

New solutions in the ferrates(VI) process with the use of SnО₂–modified electrodes

Изучены особенности образования ферратов(VI) из соединений Fe(III) в растворах с различным ионным составом на инертных SnО₂-электродах, легированных Ru, Pt, Pd и Sb. Установлено, что изменением природы и содержания легирующего металла можно целенаправленно регулировать электро-каталитические свойства анодов, в частности величину перенапряжения выделения О₂. Показана принципиальная возможность электрохимического окисления на поверхности электрода и химического окисления в объеме раствора частиц Fe(ОН)₃ и Fe(ОН)₄. Разработаны рекомендации для синтеза ферратов(VI) с использованием анодов, обеспечивающих длительный режим работы без ухудшения их эксплуатационных характеристик.Disadvantages of traditional synthesis methods of ferrates (VI) - promising green oxidants - stimulate the search of new technological solutions which meet the requirements of modern production. The purpose of this work was to study the ferrates (VI) formation from Fe (III) compounds in solutions with different pH on inert SnО₂ electrodes doped with Pt, Ru, Pd, and Sb. The influence of the nature and the content of the alloying metal on the electrocatalytic properties of the electrode was studied by the stationary voltammetry method, as well as by determining the current yields of hypochlorite and sodium chlorate during the electrolysis of a slightly alkaline NaCl solution. Coatings based on SnО₂, doped with palladium and platinum, show maximal electrocatalytic activity according to ClO – synthesis. It has been established that the oxygen evolution overvoltage on the electrodes with comparable dopant concentrations increases in the Ru-Pd-Pt-Sb series. It has been shown that for effective synthesis of ferrates (VI), flat Ti anodes of a large area with an electroactive layer based on SnО₂-Sb2О₃ should be used. It is noted that electrochemical oxidation of Fe (III) in Fe (VI) is more energetically favorable on these electrodes than О₂ evolution, which opens up new possibilities for these processes in ferrate (VI) synthesis technology. We have shown the principal possibility of increasing the productivity of the Fe (VI) process due to the direct interaction of the Fe(ОН)₃ and Fe(ОН)₄− particles in the solution volume with ClO− anions generated on an inert electrode when Сl− anions are preliminarily added to the system. Technological solutions have been proposed to increase the life of inert electrodes when 5-10% TiO2 is introduced into the SnО₂ matrix, providing a long-term operating mode without degradation of their performance characteristics

Effects of ultrasound on electrochemical oxidation mechanisms of p-substituted phenols at BDD and PbO2 anodes

The effects of low-frequency (40 kHz) ultrasound are investigated with regard to the effectiveness and mechanisms of electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) at BDD (boron-doped diamond) and PbO2 anodes. Although ultrasound improved the disappearance rates of p-substituted phenols at both the BDD and PbO2 anodes, the degree of enhancement varied according to the type of p-substituted phenol and type of anode under consideration. At the BDD anode, the % Increase values were in the range 73-83% for p-substituted phenol disappearance and in the range 60-70% for COD removal. However, at the PbO2 anode, the corresponding %Increase values were in the range 50-70% for disappearance of p-substituted phenols and only 5-25% for COD removal, much lower values than obtained at the BDD anode. Further investigations on the influence of ultrasound on the electrochemical oxidation mechanisms at BDD and PbO2 anodes revealed that the different increase extent were due to the specialized electrochemical oxidation mechanisms at these two anodes. The hydroxyl radicals were mainly free at the BDD electrodes with a larger reaction zone, but adsorbed at the PbO2 electrodes with a smaller reaction zone. Therefore, the enhancement due to ultrasound was greater at the BDD anode than at the PbO2 anode. (C) 2010 Elsevier Ltd. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000280422800007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701ElectrochemistrySCI(E)EI21ARTICLE205569-55755

Electrocatalytic degradation of phenol on Pt- and Ru-doped Ti-SnO2-Sb anodes in an alkaline medium

[EN] In this work, the electrocatalytic performance of Ti/SnO2-Sb(13-x)-Pt-Ru(x) anodes (x = 0.0, 3.25 and 9.75 at.%) towards phenolate elimination has been analyzed and compared to those of conventional Ti/RuO2 and Ti/Co3O4 anodes, to evaluate their application for decontamination of concentrated alkaline phenolic wastewaters. The effects of the applied current density and the nature of the anode on the activity, kinetics and current efficiency for phenolate elimination, COD removal and benzoquinone by-product formation/degradation have been thoroughly examined. The Ti/SnO2-Sb-Pt anode exhibits the best electroactivity, fastest kinetics and highest current efficiency among the studied anodes, but poor electrochemical stability. The introduction of small amounts of Ru (3.25–9.75 at.%) brings about a slight loss of the electrocatalytic performance, but it causes a remarkable increase in the stability of the electrode. In terms of energy consumption and stability, the Ti/SnO2-Sb(9.75)-Pt-Ru(3.25) electrode seems to be the most promising anode material for the electrochemical treatment of alkaline phenolic wastewaters. The increase in current density generally leads to significantly faster phenolate, benzoquinone and COD degradations, but with lower efficiency because of an increasing selectivity to water oxidation. A correction of the ideal kinetic model has been proposed to predict the oxidation of organics on non-active metal oxide anodes. ©2016 Elsevier B.V. All rights reserved.Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2013-42007-P, IJCI-2014-20012) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged.Berenguer Betrián, R.; Sieben, JM.; Quijada Tomás, C.; Morallón, E. (2016). Electrocatalytic degradation of phenol on Pt- and Ru-doped Ti-SnO2-Sb anodes in an alkaline medium. Applied Catalysis B: Environmental. 199:394-404. https://doi.org/10.1016/j.apcatb.2016.06.038S39440419

Recent progress in Ti-based nanocomposite anodes for lithium ion batteries

Studying on the anode materials with high energy densities for next-generation lithium-ion batteries (LIBs) is the key for the wide application for electrochemical energy storage devices. Ti-based compounds as promising anode materials are known for their outstanding high-rate capacity and cycling stability as well as improved safety over graphite. However, Ti-based materials still suffer from the low capacity, thus largely limiting their commercialized application. Here, we present an overview of the recent development of Ti-based anode materials in LIBs, and special emphasis is placed on capacity enhancement by rational design of hybrid nanocomposites with conversion-/ alloying-type anodes. This review is expected to provide a guidance for designing novel Ti-based materials for energy storage and conversion. Keywords: lithium-ion batteries (LIBs) anode titania lithium titanateNational Natural Science Foundation (China) (51472137)National Natural Science Foundation (China) (51772163

Electrochemical degradation of 4-chlorophenol at nickel-antimony doped tin oxide electrode

The effectiveness of a novel nickel-antimony doped tin oxide electrode for electrochemical degradation of organic pollutants was investigated using 4-chlorophenol (4-CP) as a model toxic organic. The experimental results demonstrate that the optimal Ni content was at Ni:Sn = 1:500 in atomic ratio in the precursor coating solution, whereas the Sb:Sn ratio was set at 8:500. Using the electrode prepared with the optimal Ni doping ratio for 4-CP degradation, the charge-based efficiencies were up to 89 μg C -1 for 4-CP destruction and 15 μg C -1 for TOC removal, which were considerably higher than the efficiencies observed for other electrodes. It is suggested that the enhancement of the electrode for electrochemical oxidation of organics could be attributed to the production of hydroxyl radicals in anodic water electrolysis. © 2006 Elsevier Ltd. All rights reserved.postprin