Enhanced electrochemical behavior of ceria based zirconia electrolytes for intermediate temperature solid oxide fuel cell applications

摘要

Ceria based zirconia solid electrolytes for intermediate temperature solid oxide fuel cells were synthesized using a simple and environment-friendly sol-gel route via hydrolysis process. Influence of Zr~(4+) ions on three different compositions Ce_(0.8)Zr_(0.2)O_(1.9), Ce_(0.7)Zr_(0.3)O_(1.85)and Ce_(0.6)Zr_(0.4)O_(1.8) were investigated. Phase identification and cell parameters were determined by powder X-ray diffraction studies. Rietveld refinement was confirmed the synthesized cerium zirconium oxide possess a cubic fluorite type structure. BET surface analysis exhibited that the materials which possessed high surface area may increase the probability of effective electron transport at the electrode/electrolyte interface. Charge-transfer transition from O~(2-)(2p) to Ce~(4+)(4f) orbitals in cerium oxide were examined by UV-vis and photoluminescence studies. The Zr~(4+) ions on cerium lattice create the oxygen vacancy and lead to the formation of Ce~(3+) from Ce~(4+). The electrical conductivity was analyzed using electrochemical impedance spectroscopy. CZ0.4 showed a higher electrical conductivity of 0.745 × 10~(-3) Som~(-1) and lower activation energy of 0.97 eV at 600 ℃ than the other compositions. The incorporation of Zr~(4+) ions influence to reduce the ionic band between Ce and O, which makes the motion of oxygen as flexible and it was confirmed with cyclic voltammetry analysis. The stability of electrolyte was examined by chronoamperometry studies. A very quick current drop (t = 0.17 s) was revealed the stability of electrolyte. Hence, these results suggest that the modified ceria based zirconia solid electrolytes can be a suitable material for solid oxide fuel cell applications.