Comparison of GDC electrolyte-LSCF cathode IT-SOFC system with conventional power sources

Abstract

Remarkably high electrical efficiency at attractive economics can be achieved by using Ce_0.8Gd_1.2O_1.2 (Gadolinium Doped Ceria (GDC)) as solid electrolyte in IT-SOFC (Intermediate Temperature-Solid Oxide Fuel Cell) and using La_1-xSr_xCo_1-yFe_yO_3-δ (LSCF) as cathode where, 0 <; x ≤ 0.5, 0 <; y ≤0.8. Different solid oxide electrolyte samples were synthesized employing dry pressing technique, thereafter the samples were sintered at different temperatures ranging from 1350°C to 1600°C. Relative density as high as 93.93% was achieved for electrolyte samples. X-Ray Diffraction (XRD) pattern for sintered GDC samples reveals the presence of crystalline crystallographic system of cubic phases with crystal orientation such as (111), (200), (220), (311), (222), (400), (331), (420), thereby ensuring productive sintering. Impedance Analysis at different temperatures indicates that the ionic conductivity increases with the increase in sintering temperature and was found to attain its peak value at 1550 °C. Exceptionally high power density of 347mW/cm², 539mW/cm² and 747mW/cm² of 700 °C, 750°C and 800 °C were achieved indicating excellent electrolytic performance. This justified the competency of GDC to replace conventional YSZ (Yttrium Stabilized Zirconia) electrolyte. Further, different cathode samples were synthesized using combustion synthesis technique, thereafter the samples were sintered at different temperatures ranging from 1050°C to 1150°C for 4 hours in air. Single phase rhombohedral of LSCF is obtained and is confirmed by the peaks corresponding to (104), (110), (024), (300) and (306). Surface area of the sample having highest cobalt concentration is found to be much higher than other samples, that is, 14.579 m²/g. TG graphs shows that drastic weight loss occurs in three steps in the temperature range of 195-200 °C, 300-340 °C and 430-460 °C. Arrhenius plot suggests that DC conductivity increases with increase in densification for sample having lowest cobalt concentration while decreases in case of other samples, Of all the prepared samples, La_0.54Sr_0.4Co_0.8Fe_0.2O_3±δ was found to be most efficient as it achieved current density as high as 2.12A/cm² at 800 °C under cell operation voltage of 0.7 V. Hence the GDC electrolyte and LSCF cathode IT-SOFC fuel cell system can deliver attractive economics and consequently can be used for the production of clean energy allowing sustainable development.