Fluorine doping for the enhanced electrochemical performance of SrCo0·8Ti0·2O3-based perovskite cathode for Solid Oxide Cells
Fluorine doping in the oxygen sublattice has been previously employed to modify the physicochemical properties of perovskite-type oxides. However, the underlying mechanism responsible for the observed enhancements remains unclear. In this study, we systematically investigate the effects of F-doping on the crystal structure, electronic properties, oxygen ion transport, and electrochemical performance of SrCo 0 · 8 Ti 0 · 2 O 3- x - δ F x cathodes through a combination of experimental and DFT theoretical computation methods. The results indicate that the samples retain a cubic structure, while F-doping reduces the valence state of Co and decreases the oxygen vacancy concentration. Although the thermal expansion coefficients of SCTF x remain unchanged, the electrical conductivity of the F-doped SCTF 0.1 is improved. Partial substitution of F for O effectively increases the oxygen diffusion coefficient and reduces the polarization resistance in the charge transfer process, thereby enhancing the catalytic activity of the SCTF 0.1 cathode. The polarization resistance of SCTF 0.1 is as low as 0.050 Ω cm 2 at 700 °C. Notably, the peak power densities of a full cell with the SCTF 0.1 cathode exhibit a significant boost, particularly at lower temperatures. Theoretical calculations corroborate the experimental findings, demonstrating that F-doping effectively reduces the oxygen migration barrier. Overall, fluorine doping proves to be an effective strategy for optimizing SrCo 0 · 8 Ti 0 · 2 O 3 -based SOC cathodes.
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