Electrochemical characterization of halide ions adsorption from ionic liquid mixtures at Bi(111) and pyrolytic graphite electrode surface
Date
2016-07-05
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Abstract
Ökoloogilise jalajälje vähendamiseks vajame me seadmeid, mis aitaks meil edukalt energiat muundada ja salvestada ning liikuda alternatiivsemate energiatootmise meetodite poole võrreldes fossiilsete kütustega. Energiatootmis- ning salvestusseadmeid on palju, kuid neil on üks ühine osa – elektrolüüt. Superkondensaatorite, patareide, päikesepatareide ja kütuselementide korral sõltub nende efektiivsus ja eluiga väga palju kasutatud elektrolüüdist. Klassikalised vesilahustel põhinevad elektrolüüdid ei võimalda meil disainida suure energia ja võimsustihedusega kondensaatoreid, sest limiteerima hakkab vee elektrokeemiline lagunemine. Samuti on paljude orgaaniliste solventide kasutamisel sama probleem ning lisaks ei saa neid elektrolüüte kasutada kõrgel temperatuuril intensiivse aurustumise tõttu. Toatemperatuuril vedelad soolad ehk ioonsed vedelikud võimaldavad lahendada eelmainitud probleeme, olles keemiliselt ja elektrokeemiliselt stabiilsed elektrolüüdid laias potentsiaalide ja temperatuuride vahemikes. Ioonseid vedelikke on võimalik disainida miljoneid kombineerides erinevaid katioone ja anioone ning mõjutades seeläbi elektrolüüdi omadusi.
Elektroodi ja elektrolüüdi piirpinnal toimuvad protsessid on olulised fundamentaal ja praktilise elektrokeemia arendamise seisukohast. Struktuur, kuidas paiknevad positiivsed ja negatiivsed osakesed elektroodi pinnal, mõjutab oluliselt energiasalvestus seadmete tööd ja eluiga. Teadustöö eesmärgiks oli uurida ioonsete vedelike kui elektrolüütide käitumist vismut ja süsinikelektroodi pinnal. Mõõtmised viidi läbi mitmes erinevas ioones vedelikus ning nende segudega. Anioonidest keskenduti halogeeniididele, sest varasemalt on teada, et jood ja broom omavad tugevat adsoprtsiooni nii vismuti kui ka süsinikmaterjalidel. Süsteemi elektrokeemiliseks karakteriseerimiseks kasutati tsüklilist voltamperomeetria ja elektrokeemilise impedantsspektroskoopia meetodeid. Samuti võrreldi saadud tulemusi arvutuskeemia ning skaneeriva tunnelmikroskoopia tulemustega. Leiti, et halogeniidide lisamine ioonesete vedelike koostisse mõjutab oluliselt elektrilise kaksikkihi parameetreid ning tõstab mahtuvuse väärtusi. Leiti, et käsitletud elektrolüüdid sobivad kasutamiseks superkondensaatorites.
Reducing of the ecological footprint is the main goal in future energy technology. Developing of new high effective energy storage and conversion systems allows us to move towards alternative energy sources. Supercapacitors, solar cells and fuel cells, like other modern electrochemical devises, need better electrolytes for more efficient work. Some ionic liquids (IL) can be environmentally friendly and more stable electrolytes for energy devices. Ionic liquids are one of the materials that impact on a broad swath of energy systems performance and offer an opportunity to optimize the performance of electrochemical device by choosing cation and anion as needed. Nowadays the characterization of the interface between the metal electrode and IL is the first priority of interfacial electrochemists to develop novel electrolytes for high energy density devices. In this work the electrochemical characterization of interface between bismuth single crystal or pyrolytic graphite electrodes and IL or their mixtures as an electrolytes have been concluded. Halides are attractive parts for electrolyte designing, ensuring sometimes reversible redox reaction as well as increasing ionic conductivity of the system. For the practical point of view, halides are cheap and ecologically friendly anions. In this work iodide and bromide anions specific adsorption onto the electrode surface has been investigated. Cyclic voltammetry, electrochemical impedance spectroscopy, in situ STM and computational methods were used. It was found that ionic liquids and their mixtures with halide ions additions are excellent electrolytes for modern electrochemical devices, especially for supercapacitors. The electrode potential, chemical composition of electrolyte and electrode material influences strongly the electrical double layer parameters and especially capacitance values. It is certainly worth mentioning that very good reversibility and high stability characteristics were achieved in the case of studied mixtures.
Reducing of the ecological footprint is the main goal in future energy technology. Developing of new high effective energy storage and conversion systems allows us to move towards alternative energy sources. Supercapacitors, solar cells and fuel cells, like other modern electrochemical devises, need better electrolytes for more efficient work. Some ionic liquids (IL) can be environmentally friendly and more stable electrolytes for energy devices. Ionic liquids are one of the materials that impact on a broad swath of energy systems performance and offer an opportunity to optimize the performance of electrochemical device by choosing cation and anion as needed. Nowadays the characterization of the interface between the metal electrode and IL is the first priority of interfacial electrochemists to develop novel electrolytes for high energy density devices. In this work the electrochemical characterization of interface between bismuth single crystal or pyrolytic graphite electrodes and IL or their mixtures as an electrolytes have been concluded. Halides are attractive parts for electrolyte designing, ensuring sometimes reversible redox reaction as well as increasing ionic conductivity of the system. For the practical point of view, halides are cheap and ecologically friendly anions. In this work iodide and bromide anions specific adsorption onto the electrode surface has been investigated. Cyclic voltammetry, electrochemical impedance spectroscopy, in situ STM and computational methods were used. It was found that ionic liquids and their mixtures with halide ions additions are excellent electrolytes for modern electrochemical devices, especially for supercapacitors. The electrode potential, chemical composition of electrolyte and electrode material influences strongly the electrical double layer parameters and especially capacitance values. It is certainly worth mentioning that very good reversibility and high stability characteristics were achieved in the case of studied mixtures.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
elektrolüüdid, faasieralduspinnad, halogeniidid, ioonid, adsorptsioon, electrolytes, interfaces (chemistry), halides, ions, adsorption