Interfacial structure and adsorption of organic compounds at Cd(0001) and Sb(111) electrodes from ionic liquid and aqueous electrolytes: an in situ STM study
Date
2015-09-28
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Tänapäeva teaduses on olulised teemad molekulaartehnoloogia ja energia salvestamine. Elektroonika tootjad üritavad valmistada järjest väiksemaid ja kõrgemate tehniliste näitajatega mobiiltelefone, arvuteid jmt seadmeid.
Üks meetod selle saavutamiseks on väiksemate ja võimsamate elektrooniliste komponentide arendamine, mis oleksid suurema mäluga. Siin tulebki mängu molekulaarelektroonika- kui transistori suurust saaks kahandada ühe molekulini, siis oleks võimalik ruutsentimeetrisele kiibile salvestada kuni miljon korda rohkem infot kui praegu.
Energiasalvestustehnoloogias on üheks tähelepanu keskpunktiks ioonsed vedelikud, mis leiavad kasutust energiasalvestusseadmetes, nt superkondensaatorites ja patareides, kuna nad on stabiilsed laias potentsiaalide vahemikus ja rakendatavad nii elektrolüüdi kui ka lahustina.
Kõik mainitud arendussuunad nõuavad aga täpset arusaama elektrood-elektrolüüt piirpinnal toimuvatest adsorptsiooniprotsessidest ning nende sõltuvusest elektroodi potentsiaalist.
Antud töö eesmärkideks oli uurida Cd(0001) ja Sb(111) monokristalsete elektroodide pinnale moodustunud faasidevahelise piirpinna ehitust erinevates elektrolüütides, milleks rakendati in situ skaneeriva tunnelmikroskoopia (STM) meetodit. In situ STM meetodiga on võimalik reaalajas visualiseerida elektroodi pinnastruktuur atomaarsel tasandil.
Töö käigus näidati, et Cd(0001) ja Sb(111) elektroodide pinnastruktuur ei sõltu uuritud potentsiaalide vahemikus pindinaktiivses vesilahuses ega ka ioonses vedelikus elektroodi potentsiaalist.
Uuriti ka 4,4′-bipüridiini adsorptsiooni Cd(0001) elektroodile fooni lahusest ning 2,2′ bipüridiini adsorptsiooni Sb(111) elektroodile ioonsest vedelikust. Selgus, et 4,4′ bipüridiini molekulid moodustavad Cd(0001) elektroodile paralleelselt asetsevad molekulread pinnakatvusega 4,73×10−10 mol cm−2. Ka 2,2′-bipüridiini molekulid adsorbeeruvad Sb(111) pinnale ioonsest vedelikust spetsiifilise mustriga, kuid seda märgatavalt tihedamalt andes väga kõrge piirilise adsorptsiooni väärtuse 7,72×10−10 mol cm−2.
Nowadays the main focus in science is on molecular technology and energy storage. All electronic devices like phones, computers, etc. have trend to be miniaturised, but at the same time offering a higher level of performance. One method to achieve this is to create smaller electronic components and memory modules, providing at the same time better performance and higher memory capacity. Hence the importance of molecular technology – if the size of a single transistor would be one molecule then it would be possible to save a million times more data to a cm-sized chip than today. In energy storage applications ionic liquids have gained a lot of attention due to high stability under applied electrode potential and thus applicable in various electrical power sources, including supercapacitors and novel batteries. All the mentioned development directions demand an extensive understanding of adsorption processes at electrode|electrolyte interface. In this work the in situ scanning tunneling microscopy (STM) method has been applied to study the interfacial structure of Cd(0001) and Sb(111) single crystal electrodes in various electrolytes including ionic liquids. In situ STM method enables to visualise the surface structure of an electrode at atomic scale and to study the influence of the electrode potential to the interfacial structure. The studies revealed that the surface structure of Cd(0001) and Sb(111) electrodes are stable in a wide potential region in ionic liquid and aqueous electrolytes. The adsorption of 4,4′-bipyridine (4,4′-BP) from aqueous solution on Cd(0001) electrode and the adsorption of 2,2′-bipyridine (2,2′-BP) from ionic liquid on Sb(111) electrode has been analysed. It was demonstrated that at moderate negative electrode potentials the adsorbed 4,4′-BP molecules form stripes on Cd(0001) surface with an adlayer coverage of 4.73×10−10 mol cm−2 2,2′-BP also forms a distinctive pattern at the Sb(111) surface. However, this formed layer is significantly denser and the adlayer coverage is a very high 7.72×10−10 mol cm−2.
Nowadays the main focus in science is on molecular technology and energy storage. All electronic devices like phones, computers, etc. have trend to be miniaturised, but at the same time offering a higher level of performance. One method to achieve this is to create smaller electronic components and memory modules, providing at the same time better performance and higher memory capacity. Hence the importance of molecular technology – if the size of a single transistor would be one molecule then it would be possible to save a million times more data to a cm-sized chip than today. In energy storage applications ionic liquids have gained a lot of attention due to high stability under applied electrode potential and thus applicable in various electrical power sources, including supercapacitors and novel batteries. All the mentioned development directions demand an extensive understanding of adsorption processes at electrode|electrolyte interface. In this work the in situ scanning tunneling microscopy (STM) method has been applied to study the interfacial structure of Cd(0001) and Sb(111) single crystal electrodes in various electrolytes including ionic liquids. In situ STM method enables to visualise the surface structure of an electrode at atomic scale and to study the influence of the electrode potential to the interfacial structure. The studies revealed that the surface structure of Cd(0001) and Sb(111) electrodes are stable in a wide potential region in ionic liquid and aqueous electrolytes. The adsorption of 4,4′-bipyridine (4,4′-BP) from aqueous solution on Cd(0001) electrode and the adsorption of 2,2′-bipyridine (2,2′-BP) from ionic liquid on Sb(111) electrode has been analysed. It was demonstrated that at moderate negative electrode potentials the adsorbed 4,4′-BP molecules form stripes on Cd(0001) surface with an adlayer coverage of 4.73×10−10 mol cm−2 2,2′-BP also forms a distinctive pattern at the Sb(111) surface. However, this formed layer is significantly denser and the adlayer coverage is a very high 7.72×10−10 mol cm−2.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
elektroodprotsesside keemia, faasieralduspinnad, adsorptsioon, chemistry of electrode processes, interfaces (chemistry), adsorption