Integrated characterization and design of cathode microstructure for high performance solid oxide fuel cells
Author(s)
Xie, Zheng
Type
Thesis
Abstract
A composite electrode made of Pr4Ni3O10±δ-Ce0.75Gd0.1Pr0.15O2−δ was investigated in this work. Pr4Ni3O10±δ is a mixed ionic-electronic conducting phase and electrochemically active for the oxygen reduction reaction occurring within the cathode. Ce0.75Gd0.1Pr0.15O2−δ, an ionic conductor, is to extend the active sites for the oxygen reduction reaction from the electrode-electrolyte interface to the bulk of the composite cathode.
Initially, various cathodes were designed by varying the electrode thickness and the particle size of Pr4Ni3O10±δ. The microstructures of these cathodes were quanti- tatively analyzed through focused ion beam-scanning electron microscopy and subsequent 3D reconstruction. Electrochemical impedance spectroscopy was applied to characterize the impedance of the cathodes and the distribution of relaxation time supported the analysis regarding the deconvolution of impedance spectra. It was found that the steps of the oxygen reduction reaction exhibited different dependencies on both the cathode thickness and the particle size of Pr4Ni3O10±δ. The key to designing the cathode microstructure lies in balancing each step to achieve a lower area-specific resistance. Among these cathodes, the one with the lowest area-specific resistance is 0.055 Ω cm2, measured at 670 ◦C under pO2 of 0.21 atm. Additionally, an anode-supported full cell was fabricated and tested based on this cathode. The peak power density at 800 ◦C is 1.01 W cm−2.
Subsequently, cathodes with a layered structure were designed. The layered structure was confirmed to exhibit a lower area-specific resistance by simultaneously maintaining the advantages of different particle sizes. The lowest area-specific resistance obtained from layered cathodes is 0.059 Ω cm2, measured at 625 ◦C under pO2 of 0.21 atm (0.030 Ω cm2, measured at 670 ◦C under pO2 of 0.21 atm).
Initially, various cathodes were designed by varying the electrode thickness and the particle size of Pr4Ni3O10±δ. The microstructures of these cathodes were quanti- tatively analyzed through focused ion beam-scanning electron microscopy and subsequent 3D reconstruction. Electrochemical impedance spectroscopy was applied to characterize the impedance of the cathodes and the distribution of relaxation time supported the analysis regarding the deconvolution of impedance spectra. It was found that the steps of the oxygen reduction reaction exhibited different dependencies on both the cathode thickness and the particle size of Pr4Ni3O10±δ. The key to designing the cathode microstructure lies in balancing each step to achieve a lower area-specific resistance. Among these cathodes, the one with the lowest area-specific resistance is 0.055 Ω cm2, measured at 670 ◦C under pO2 of 0.21 atm. Additionally, an anode-supported full cell was fabricated and tested based on this cathode. The peak power density at 800 ◦C is 1.01 W cm−2.
Subsequently, cathodes with a layered structure were designed. The layered structure was confirmed to exhibit a lower area-specific resistance by simultaneously maintaining the advantages of different particle sizes. The lowest area-specific resistance obtained from layered cathodes is 0.059 Ω cm2, measured at 625 ◦C under pO2 of 0.21 atm (0.030 Ω cm2, measured at 670 ◦C under pO2 of 0.21 atm).
Version
Open Access
Date Issued
2024-01-02
Date Awarded
2024-04-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Skinner, Stephen
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)