Study of Structural, Thermoelectric and Electrochemical Analysis of LaSrCoFeO Cathode Materials Prepared by Different Methods

Abstract

World is moving towards renewable energy sources to avoid carbon dioxide emission causing global warming and climate change. Solid oxide fuel cells SOFCs are one of the best alternatives for energy production due to its maximum energy conversion and zero/low emission. To use biogas as a clean and high energy conversion, SOFC is the good option. However, there are still some complications that need to be addressed; one of the significant challenges, activity of SOFC at low temperature is decreased because of interfacial polarization obstructions and also oxygen reduction reaction (ORR). Thus, to improve the activity and ORR, Lanthanum based perovskite structured cathode materials were synthesized. The proposed materials were Lanthanum Strontium Cobalt Ferric oxide (La1−xSrxCo1−yFeyO3–δ (LSCF)), where x=0.3 and y=0.7. Samples were prepared by different methods such as: sol-gel method, co-precipitation method, solid state reaction method and ball milling method. The structural properties were analyzed through Raman, FTIR and XRD.UV visible analysis were also implemented to check the direct and indirect band gap of La0.7Sr0.3Co0.3Fe0.7O3-δ prepared by different methods. Electrical Impendence Spectroscopy was uses to check the conductivities of the prepared samples at different temperatures. Results revealed the Rhombohedral Structure of LSCF belongs to the R3c space group. FTIR Spectra shows the absorption peaks at 650cm-1, 656cm-1, 657cm-1, is due to the stretching vibration of Co-O/Fe-O in LSCF perovskite structure. The maximum conductivity was obtained 0.08 S/cm at intermediate temperature of LSCF which was prepared by Co Precipitation Method. This suggests that resistance lowers as temperature rises, leading to an increase in conductivity and ORR as well. La0.7Sr0.3Co0.3Fe0.7O3- δ, which was made using the co-precipitation method, has a direct band gap of 2.51 eV. This sample has the lowest band gap of all the samples made using various methods. AC conductivity is measured by four-point probe spectroscopy for the LSCF cathodes. The data obtained from four-point probe spectroscopy electrical conductivity for all prepared cathode sample is calculated At Intermediate temperature (500°C) material with different methods such as sol-gel, co- precipitation, solid state reaction and ball milling give maximum conductivity such as 0.049,0.0889,0.0250 and 0.0159 respectively. The La0.7Sr0.3Co0.7Fe0.7O3–δ has maximum conductivity of 0.0889 Scm -1 at 500 °C prepared by co-precipitation method. The maximum value of OCV and current for the prepared pallets are 0.53V and 0.011A respectively. Whereas the maximum value of current density and power density is 17.18mA/cm2 and 2.88mW/cm2 respectively at 600℃.