Facile synthesis of doped ceria-based oxide by co-precipitation technique and performance evaluation in solid oxide fuel cell

Co-precipitated nanocrystalline gadolinium (Gd)-doped ceria (CeO₂) has been synthesized with varying mole ratios of Gd in CeO₂ from 0.1-0.8 with intricate maintenance of solution pH. Phase pure Gd-doped CeO₂ (CGO) is obtained after calcination at 750°C and depending on the mole % dopant concentration, the typical crystallite size is found to vary in the range 9-27 nm. Careful observation reveals that, calcined particle size decreases with the decrease in Gd content and an optimization of the particle size with exposed (111) [stable] and (100) plane [reactive] happens to occur for Ce_0.8Gd_0.2O_2−δ (CG_0.8). High resolution transmission electron micrograph of CG_0.8 reveals highly interpenetrating lattice planes corresponding to cubic fluorite structure. The effectivity of such CG_0.8 is further supported by its high electrical conductivity of 0.02 and 0.105 S/cm @ 600 and 700°C respectively. The bulk impedances exhibit ohmic (R₀) and interfacial (R_p) polarizations to be 146 and 29.96 Ω cm² at a temperature of 600 and 700°C with activation energies 0.36 and 0.8 eV respectively. The application of CG_0.8 is further established as an interlayer in nickel oxide-yittria stabilized zirconia (NiO-YSZ)/YSZ/CGO/La-Sr-Co-Fe-based single cell with a current density of 1.2 A/cm² @ 0.5 V and 700°C using hydrogen as the fuel and oxygen as the oxidant.