Синтез та дослідження фізико-хімічних властивостей твердих електролітів на основі гідратованих гетерополікислот

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dc.contributor.advisorЛінючева, Ольга Володимирівна
dc.contributor.authorМатвєєв, Олександр Михайлович
dc.date.accessioned2020-07-07T08:35:24Z
dc.date.available2020-07-07T08:35:24Z
dc.date.issued2020-05
dc.description.abstractenScientific and technological development requires the creation of new materials with specified properties. A prospective material for chemistry and solid-state physics is solid electrolytes with ionic conductivity based on heteropolyacids. Creating a solid electrolyte with high electrical conductivity will solve a number of practical issues. Solid electrolytes (SE) have become widely used in highly efficient and environmentally friendly fuel cells, electrochemical sensors, electrochromic systems, organic synthesis. As solid electrolytes are second type conductors, electrical conductivity is due to ions. The high-conductivity electrolytes which the charge transfer is carried out by protons. Scientific interest in proton conductivity is related to the characteristics of hydrogen ions: anomalous mobility, small size and mass, the absence of an electron shell. The study of the mechanism of proton transport in SE is complicated by the simultaneous influence on their physical and chemical properties of many factors. The parameters of transport are determined by the characteristics of crystalline and microstructure and depend on the external conditions: temperature, humidity and others. There are a wide range of compounds that have proton conductivity. The proton conductivity of heteropolyacids is due to the high concentration of protons involved in transport. There are two perspectives on the conductivity of inorganic heteropolyacids. Some authors believe that they should be referred to as "globular" hydrates. The other is that the water molecules are located in the structure and then the proton conductivity depends on the structural features. The electrical conductivity of heteropolyacids depends essentially on the number of water molecules. Removing of protons leads to sharp decrease in conductivity. One promising compound in which proton conductivity is observed is polyantimony acid (PAA, antimony pentoxide hydrate, antimony acid, polyantimony acid). PAA also has ion-exchange properties, is quite persistent in the environment, inert to radiation. The last property of PPA allows to create devices based on it that will be able to work in radiation-contaminated environments. Therefore, antimony pentoxide hydrate is a promising material and needs further investigation. There is no single theory in the literature regarding the effect of synthesis conditions on the physicochemical properties, and the method for producing highconductivity PAA, which is why practicing high-conductivity PAA is an urgent task. Relationship with working with scientific programs, plans, topics. Master's thesis was being carried out pursuant to a of the state budget applied development №2209п "Sensory means of environmental monitoring and technological principles of water purification on the basis of the latest nanodispersed adsorption materials" at Department of Electrochemical Productions Technology of Igor Sikorsky Kyiv Polytechnic Institute The purpose of this work is to study the physicochemical properties of solid electrolytes based on hydrated heteropolyacids and to create a technique for the synthesis of solid electrolytes with specified properties. To achieve this goal it is necessary to solve the following problems: – to synthesize samples of solid electrolyte according to the methods available in the literature; – to establish the structural formula and morphology of the obtained samples; – to investigate the influence of humidity on the conductivity; – determine the size of the electrochemical stability of the solid electrolyte; – determine the exchange capacity of the solid electrolyte as an indicator of ionic conductivity; – to establish the possibility of using synthesized samples of solid electrolytes as a component of electrochemical systems. The object of study - hydrated heteropolyacids of antimony with proton conductivity. The subject of the study is the influence of the conditions of synthesis of hydrated heteropolyacids on their physical and chemical properties. Research Methods. Both physical and electrochemical methods were used in the work: X-ray powder diffractometry, scanning electron microscopy, cyclic voltammetry, chronoamperometry, pH-metry. Scientific novelty. The influence of the synthesis method on the chemical composition, morphology and proton conductivity of the solid electrolyte based on the hydrate of the heteropolyacid of antimony is established. The possibility of using such a solid electrolyte in electrochemical energy converters is shown. The practical significance of the results obtained. It is established that the value of the "electrochemical stability window" allows the use of the hydrobromicacid hydrate of antimony as a solid electrolyte in the cell to produce hydrogen. The technique of synthesis of phosphate-polyantimonic acid, which is characterized by high electrical conductivity and sustainability, is proposed. The use of synthesized samples of solid electrolyte in chemical sensors, which are chemical sources of current with gas depolarization, is suggested. Test results. The results of the research on the topic of the master's thesis have been tested at the VII International Conference of Students, Graduate Students and Young Scientists in Chemistry and Chemical Technology (Kyiv, 2018), XX International Scientific and Technical Conference of Students, Graduate Students and Young Scientists "Chemistry and Modern Technologies" (m. Dnipro, 2019), The International Competitive Tender of Students' Research Papers on Certain Disciplines (Kremenchuk, 2019), 4th ISE Satellite Student Regional Symposium on Promotional Materials and Processes in Applied Electrochemistry (Kyiv, 2019), XXI International Scientific and Practical Conference "News of Modern Science" (Vinnytsia, 2019), XXII International Scientific Conference active Internet conference: "Science and Education: Achievements and Development Strategies" (Dnipro, 2019). Publications. Under the topic of the master's thesis, 4 abstracts were published and the article was published in English in Hydrated Antimonic Acid as a Solid Electrolyte in Materials Today: Proceedings, which is a part of Scopus scientific-metric database. Structure and scope of work. The master's thesis consists of an introduction, four sections, conclusions, a list of references and annexes. The total volume of 105 pages, the main text occupies 78 pages, including 9 tables, 32 figures and 5 annexes. The list of references includes 98 references. The first section provides a literary overview of the state of development of solid electrolytes based on the hydrate of heteropolyacids: a general classification of solid electrolytes; solid protons with proton conductivity; proton transfer mechanisms; structure of hydrated heteropolyacids; thermal stability of hydrated heteropolyacids; the influence of conditions on the amount of conductivity of the solid electrolyte; methods of synthesis of hydrated heteropolyacids; methods for modifying the structure of heteropolyacids; possible applications of solid electrolytes based on the hydrate of heteropolyacids. Heteropolyacids are characterized by a fairly high electrical conductivity under normal conditions. Proton solid electrolytes have the highest electrical conductivity due to the anomalous diffusion of protons . This will allow them to create different systems based on them, including electrochemical sensors and fuel cells. An assessment of the possibility of creating such systems can be made by examining the electrochemical behavior of the solid electrolyte by the method of polarization curves. It is also advisable to establish the influence of the synthesis technique on the magnitude of the electrical conductivity, crystallographic structure. The second section describes the method of synthesis of heteropolyacids and methods of investigation of their physicochemical properties: X-ray powder diffractometry, scanning electron microscopy, cyclic voltammetry, chrono amperometry, pH-metry. The diagram of an apparatus for a study on working of electrochemical systems is presented. The third section shows the influence of synthesis conditions on the structure, morphology, electrochemical stability, electrical conductivity, specific proton concentration. Analyzing the influence of the synthesis method on the physicochemical properties of the solid electrolyte on the basis of heteropolyacid аntimonic can be stated: depending on the method of synthesis it is possible to obtain a solid electrolyte of varying degrees of crystallization, stability, structural and chemical composition; the PPA-1 sample has the best reproducibility due to the simplest synthesis technique; the best solid electrolytes for use in applied electrochemistry are samples PAA-1, PAA-6, PAA-8; samples of PAA-2, PAA-3, PAA-4, PAA-5, PAA-7 do not meet the requirements for solid electrolyte due to low and unstable electrical conductivity and require verification in electrochemical systems whether they can provide a minimum for electrochemical reactions. The fourth section shows the possibility of using a solid electrolyte based on the heteropolyacid hydrate in two types of electrochemical systems: electrolysis and a chemical current source. The possibility of using solid electrolyte in chemical current sources with gas depolarization and in an electrochemical cell for hydrogen production is shown. The best solid electrolyte from the samples obtained was PAA-7 hydrobromic acid hydrate of stybium modified with orthophosphoric acid. Phosphate ions act as hydration-retaining agents that provide high and stable conductivity of the solid electrolyte. General conclusions The chemical formula of heteropolyacids and its modifications, which had the form H14Sb14O21(OH)42, HSbO3∙1,62H2O, Sb2O5∙1,15H2O and Sb3O6OH, are identified. The method of X-ray phase analysis showed that almost all of the obtained samples are crystalline or partially crystalline with amorphous inclusions; belong to the Fd-3m or Pm-3 crystallographic group with the following primitive cell parameters a = b = c = 10.3… 10.36 Å and α = β = γ = 90 °. The influence of heat treatment in the technological regulation of heteropolyacid production is revealed, it clearly shows on SEM-images, while the crystallinity of the precipitate is increased and the crystal sizes are reduced. The comparison of samples with heat and without heat treatment showed that the latter is the adhesion of crystals due to the large amount of water and such samples were amorphous and larger and the effect of the modifier is noticeable in the case of orthophosphoric acid - as a result very fine sediment, prone to sticking is formed. The electrical conductivity of the obtained samples of heteropolyacids was measured and its high stability over time was shown. The electrical resistivity is inversely proportional to the humidity of the environment. The electrochemical behavior of heteropolyacids was explored. The cyclic voltammograms allowed to determine the "window" of electrochemical stability of all obtained samples, which exceeds 1.5 V. The absence of transient oxidation states of antimony in heteropolyacids is proved. The exchange capacity of samples of heteropolyacids, which is in the range of 2.2… 3.0 mmol [H+]/g, was defined. It was identified that in the case of a sample of heteropolyacid obtained through lithium carbonate with heat treatment, the value was 0.9 mmol [H+]/g The possibility of using heteropolyacids as a solid electrolyte in a chemical current source with chlorine depolarization is shown. The metrological characteristics of the sensitive elements of the chlorine sensor based on heteropolyacids have been studied. It was explored the sample obtained by hydrolysis in water is characterized by a small value of normalization of the current signal less than 3 μA/ppm and the transient time exceeded 80 s. The sample obtained through lithium carbonate with heat treatment showed a satisfactory value of the normalization of the current signal of almost 4 μA/ppm and the transient time is less than 40 s. The sample obtained by hydrolysis in phosphoric acid is characterized by even better values of normalization of the current signal more than 6 μA/ppm and a speed of less than 30 s. The prospect for the use of heteropolyacids as a membrane as a component of the cell in the production of hydrogen is shown. It is demonstrated its use as membranes have advantages over diaphragm electrolysis of alkali or acid.uk
dc.description.abstractukВ магістерській дисертації проведено літературний пошук методів синтезу, фізико-хімічні властивості твердих електролітів на основі гідратованих гетерополікислот. Проведено синтез таких твердих електролітів. Встановлено структурні формули, кристалографічні групи, параметри елементарної комірки отриманих гетерополікислот. Методом скануючоїелектронної мікроскопії встановлено морфологію твердого електроліту, яка визначається методикою синтезу. Показано вплив відносної вологості на електропровідність твердого електроліту. Методом циклічної вольтамперометрії визначено величину вікна електрохімічної стабільностіта встановлено придатність до застосування синтезованих зразків полісурм’яної кислоти в електрохімічних системах для отримання неорганічних речовин.Оцінено питому концентрацію протонів у твердому електроліті. Запропоновано методику синтезу фосфат-полісурм’яної кислоти, що характеризується підвищеною електропровідністю та стабільністю. Перевірено можливість застосування твердого електроліту в мембранному електролізі добування водню. Запропоновано застосування синтезованих зразків твердого електроліту в хімічних сенсорах, які являють собою хімічні джерела струму з газовою деполяризацією визначуваним компонентом.uk
dc.format.page90 с.uk
dc.identifier.citationМатвєєв, О. Синтез та дослідження фізико-хімічних властивостей твердих електролітів на основі гідратованих гетерополікислот : магістерська дис. : 161 Хімічні технології та інженерія / Матвєєв Олександр Михайлович. - Київ, 2020 - 90 с.uk
dc.identifier.urihttps://ela.kpi.ua/handle/123456789/34834
dc.language.isoukuk
dc.publisherКПІ ім. Ігоря Сікорського.uk
dc.publisher.placeКиївuk
dc.subjectсинтезuk
dc.subjectтвердий електролітuk
dc.subjectгетерополікислотиuk
dc.subjectелектрохімічні властивостіuk
dc.subject.udc54.021+54.04+54.057+620.184uk
dc.titleСинтез та дослідження фізико-хімічних властивостей твердих електролітів на основі гідратованих гетерополікислотuk
dc.typeMaster Thesisuk

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