Tailoring BaCe0.8Y0.2O3 proton-conducting oxide with U ions for an enhanced stability.

Uranium cations were immobilized in the proton-conducting oxide BaCe 0.8 Y 0.2 O 3 (BCY) by partially replacing Ce with U. Uranium cations can be incorporated into the BCY lattice to form the new BaCe 0.7 Y 0.2 U 0.1 O 3 (BCUY) compound. This new BCUY material shows an improved chemical stability against CO 2 compared with the traditional BCY material. The first-principles calculations reveal that the doping of U elevates the energy barrier for the interaction between BCUY and CO 2 , which is the reason for the improved chemical stability. Despite the improved chemical stability, U-doping inhibits the grain growth for the BaCeO 3 proton-conducting oxide, making the grain size of the sintered BCUY reach only 0.5 μm, which is approximately one-tenth of that for BCY sintered at the same temperature. As a result, the conductivity of BCUY is 2.8 × 10−3 S cm−1 at 700 °C. The H-SOFC using a BCUY electrolyte reaches a peak power density of 237 mW cm−2 at 700 °C, which is lower than that for BCY cells, but comparable to that using other proton-conducting electrolytes. The current study demonstrates that U cations can be immobilized in BCY proton-conducting oxide, and that U-doping improves the stability of the material at the cost of reducing the sinterability, and thus conductivity. [ABSTRACT FROM AUTHOR]