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Title: Materials development and spectroscopic characterisation of solid oxide cells
Author: Manerova, Jevgenija
ISNI:       0000 0004 7431 8791
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Solid oxide cells (SOCs) are highly efficient electrochemical energy conversion devices capable of on-demand, reversible energy conversion: chemical energy into electricity and vice versa. Operating at intermediate to high temperatures, SOCs have a great potential for high conversion efficiencies using a wide variety of reactants, including carbon dioxide (CO2) and low-grade fuels such as biogas. An enhanced understanding of the electrochemical reactions occurring at the triple phase boundary (TPB) active sites of the electrodes and the cell degradation mechanisms is critical to the development of the robust, reversible SOCs. Nickel-based electrodes, commonly used in SOCs, are susceptible to carbon deposition and poisoning by contaminants, such as sulfur and silica, causing detrimental effect on the electrochemical performance of the SOCs. The research aims of this work were threefold. First of all, an electrochemical reactor capable of simultaneous vibrational Raman spectroscopy, voltammetry and electrochemical spectroscopy measurements of operating SOCs was developed; creating a high temperature operando Raman spectroscopy research capability at the University of Sheffield. Secondly, in situ formation of the carbon deposits on Ni-YSZ electrodes with applied negative bias exposed to a CO2-CO atmosphere was studied using the reactor developed previously. The applied bias has shown to promote carbon deposition on the Ni-YSZ surface. The post-mortem analysis showed carbon nanofibers formation at the NiYSZ/electrolyte interface as well as presence of larger deposits with disordered carbon structure (D1/G ratio higher than 1.5) on the electrode surface at 700 °C and 50/50 CO2/CO ratio. Lastly, a novel concept of using mixed ionic-electronic conducting oxides as SOC electrodes, consisting of a samarium-doped ceria oxygen ion-conductive phase and an oxygen-deficient cobalt iron oxide phase, to extend the reaction sites from the traditional TPB, was investigated. Samples sintered in N2 atmosphere showed increased electrical conductivity compared to the ones sintered in air.
Supervisor: Rothman, R. H. ; Sinclair, D. C. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available