The development of ceramic fuel electrode for solid oxide cells
Failid
Kuupäev
2021-04-14
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Tänapäeva ühiskonna üks olulisemaid väljakutseid on kliimamuutuste pidurdamine. Selleks tuleks oluliselt vähendada õhku paisatava CO2-e hulka. Tahkeoksiidelemendil (TOE) kui kõrge efektiivsusega energiamuundamisseadmel on selles oluline roll. TOE-d saab kasutada rohelise jääkelektri (päikesepatareidest ning tuulegeneraatoritest) muundamisel kütuseks (vesinik, sünteesgaas jne.) ja ka kütuse muundamisel tagasi elektriks. Selle tehnoloogia konkurentsivõime tõstmiseks oleks vaja alandada TOE süsteemide hinda ja parandada vastupidavust.
Käesoleva töö eesmärgiks oli uudse TOE vesinikelektroodi uurimismeetodi demonstreerimine ning elektrokeemiliselt aktiivse redoksstabiilse kütuseelektroodi arendamine. Selleks, et jälgida TOE töötamise käigus materjali sisemuses toimuvaid kristallograafilisi muutusi, disainiti uudne kõrgtemperatuurne operando röntgendifraksiooni (XRD) mõõterakk. Näidati, et selle meetodiga saadud info aitab mõista elektroodis toimuvaid dünaamilisi, töötingimustest sõltuvaid muutusi ja degradatsiooniprotsesse. Need teadmised on aidanud valmistada stabiilsemaid TOE täiselemente.
Töö teises pooles keskenduti uudsete redoksstabiilsete materjalide arendamisele. Parimaks materjaliks osutus katalüütiliselt aktiivne ning 120 h pikkustes testides väga hea stabiilsusega La0,25Sr0,25Ca0,4Ti0,95Ni0,05O3-d. Elektroodi polarisatsiooniline takistus 850 °C juures ning avatud ahela potentsiaalil oli 0,084 Ω cm2. Selle materjaliga valmistatud kütuseelemendi võimsustiheduseks saadi samal temperatuuril 325 mW cm-2.
Tackling climate change is one of the challenging yet vital problems of modern society. Solid oxide cells (SOC) as highly efficient energy conversion devices can be useful in several ways in this field. Firstly, in solid oxide electrolysis mode, the cell can convert surplus electric energy from intermittent energy sources like wind and solar to fuels. Secondly, when electricity demand is high, the conversion system is switched to a solid oxide fuel cell (SOFC) mode. It can convert chemical energy back to electrical energy. However, some issues need to be addressed to increase the stability and economic viability of SOC based devices. This work aimed to demonstrate a powerful novel approach for analysing the SOC hydrogen electrodes and to develop a robust, stable and catalytically active fully ceramic fuel electrode for SOCs. The high temperature operando X-ray diffraction (XRD) method has been developed and applied for studies of two different SOC hydrogen electrodes to understand the processes taking place in the SOC fuel electrode during its operation. This knowledge has proven useful for designing new cells with fewer degradation problems. The second part of the theses focused on developing novel redox stable electrode materials. One of these stable and catalytically active materials developed in this work is La0,25Sr0,25Ca0,4Ti0,95Ni0,05O3-d.. It has a polarization resistance value of 0.084 Ω cm2 at 850 °C and OCV conditions, and no degradation was observed during 120 h. The power density of 325 mW cm-2 was achieved in fuel cell mode using this material.
Tackling climate change is one of the challenging yet vital problems of modern society. Solid oxide cells (SOC) as highly efficient energy conversion devices can be useful in several ways in this field. Firstly, in solid oxide electrolysis mode, the cell can convert surplus electric energy from intermittent energy sources like wind and solar to fuels. Secondly, when electricity demand is high, the conversion system is switched to a solid oxide fuel cell (SOFC) mode. It can convert chemical energy back to electrical energy. However, some issues need to be addressed to increase the stability and economic viability of SOC based devices. This work aimed to demonstrate a powerful novel approach for analysing the SOC hydrogen electrodes and to develop a robust, stable and catalytically active fully ceramic fuel electrode for SOCs. The high temperature operando X-ray diffraction (XRD) method has been developed and applied for studies of two different SOC hydrogen electrodes to understand the processes taking place in the SOC fuel electrode during its operation. This knowledge has proven useful for designing new cells with fewer degradation problems. The second part of the theses focused on developing novel redox stable electrode materials. One of these stable and catalytically active materials developed in this work is La0,25Sr0,25Ca0,4Ti0,95Ni0,05O3-d.. It has a polarization resistance value of 0.084 Ω cm2 at 850 °C and OCV conditions, and no degradation was observed during 120 h. The power density of 325 mW cm-2 was achieved in fuel cell mode using this material.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Märksõnad
electrochemistry, fuel cells, solid electrolytes, oxides, electrodes