Hybrid Fuel Cells with Carbonate/Oxide Composite Electrolytes: An Electrochemical and Theoretical Insight
The aim of the current presentation is to get a deeper understanding on the origins of such improved performances by combining both experimental and modeling approaches. Experimentally, systematic studies dealing with the impact on conductivity of molten salts composition, oxide phase conductivity, environmental parameters (reducing and oxidizing atmospheres, temperature, cycling) were performed by impedance spectroscopy . Moreover, Density Functional Theory calculations were carried out to provide a better understanding on the transport mechanisms and the species involved, by first determining the most stable surface structures for both phases, separately, before building different carbonate/oxide interfaces and investigating the operating principles of these cells. Regarding the theoretical calculations, periodic DFT calculations were performed on the bulk structure of ZrO2, LiKCO3, LiNaCO3, evaluating the performances of different Gaussian-type basis sets and various exchange-correlation functionals, in order to select a reliable computational protocol that accurately describes the basic components of hybrid fuel cells. Considering the importance of the interface phenomena in composite materials, this protocol has then been used to examine the surface chemistry of the oxide and carbonate phases. The study of the electronic and structural properties of the most stable (001) and (110) surfaces of (LiK)CO3 and (LiNa)CO3 and the systematic investigation of the reducibility properties and of the stabilization of the cubic (111) of ZrO2 through doping with Y2O3 (8 mol %) allowed us to identify a suitable surface model relative to the two phases that can be used to further simulate the interface of the composite material [4,5]. As far as we know, the combination of both approaches has never been reported in the literature and the first results dealing with YSZ and Li-Na or Li-K carbonates eutectics will be presented.
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