Publication: Lanthanum strontium cobalt ferrite-nickel oxide as cathode for intermediate temperature solid oxide fuel cell
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Date
2022-03-01
Authors
Mohamed Rosli, Ahmad Zaki
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Abstract
Solid Oxide Fuel Cell (SOFC) is a device to produce high amount of energy with elevated conversion efficiency that produces water as by-product. Generally, SOFC is operated at a high temperature 1000 ºC with multiple types of fuel for the oxygen reduction reaction process. However, high capital and operating cost hinder SOFC application. Reducing operating temperature to intermediate temperature (600-800 ºC) also known as IT-SOFC can suppress the component degradation as well as improve cell durability and reduce system cost. Lowering the operating temperature decreases the electrode kinetics and increases interfacial polarization resistance and the effects is more prominent for the oxygen reduction reaction (ORR) at cathode side. To minimize the polarization resistance of the cathode, a favourable electronic and ionic conductivity along with excellent catalytic activity for oxygen reduction must be developed. In this research, NiO was added to the state-of-art cathode for IT-SOFC, which is lanthanum strontium cobalt ferrite (LSCF) forming a composite cathode LSCF-NiO. NiO was selected to be added to the LSCF because previous studies suggest that it can improve the performance by enhancing the oxygen reduction
reaction (ORR). This thesis focusing on the study regarding the impact on the physical, chemical, and electrochemical performance by utilizing the modified Pechini method.
Thermogravimetric analysis (TGA) result suggests that LSCF can form a complete perovskite structure as low as 650 ºC. Further analysis from Fourier transform infrared
spectroscopy (FTIR) confirms the complete perovskite structure formation achieved after calcined at 700 ºC. X-Ray diffraction (XRD) also showed the crystal size increase
as calcination temperature increases. These findings align with scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis where the particle size increase as increased in calcination temperature. BET result reveals the decrement of specific surface area from 18.3 to 7.9 m2/g when sintered at 700 ºC and 800 ºC, respectively. High purity and well-spread of NiO were confirmed by elemental analysis. There is no trace of gadolinium-doped ceria (GDC) in composite cathode LSCF-NiO via Energy Dispersive X-ray (EDX) indicating good chemical compatibility between the LSCF-NiO and GDC. The Electrochemical Impedance Spectroscopy (EIS) result shows that the LSCF-NiO 800 has a low polarization resistance, Rp of 0.07 Ω cm2 when tested at 800 ºC. The activation energy, Ea obtained was 159.5 kJ/mol. This suggests that LSCF-NiO 800 is suitable to be used as a cathode for IT-SOFC.