Single composite electrolyte prepared by infiltration and characterization

Abstract

Oxygen-ion and proton-conducting electrolytes should be combined into a composite to improve fuel cell capacity and electrocatalytic efficiency. To realize a single membrane of a composite electrolyte with dual charge carriers, we use only a single process. A BaZr0.8Ni0.01Y0.19O3 (BZNY) proton-conducting electrolyte solution and suspension are infiltrated into a porous oxygen-ion-conducting electrolyte (La0.75Sr0.2Ba0.05)0.175Ce0.825O1.891 (LSBC) substrate using a simple pumping process. The infiltration of BZNY into the porous LSBC results in a gradient composition of BZNY. The obtained single-composite electrolyte, BZNY-LSBC, possesses individual perovskite and fluorite crystal structures after sintering. The BZNY solution infiltrates the porous LSBC substrate to a smaller depth than the phase-preformed nano-BZNY slurry. The effective infiltration depth is approximately 50 mu m for the BZNY solution, and 300 mu m for the nano-BZNY into a 400 mu m thickness of LSBC. The infiltrated composite electrolyte exhibites lower conductivity compared to the solid-state-prepared single-phase LSBC electrolyte at 600 degrees C, but almost the same conductivity at 800 degrees C from the AC impedance analyses. When the Sr2Fe1.5Mo0.5O6 (SFM) are applied as symmetric electrodes, the SFM|BZNY-LSBC|SFM fuel cells maintain the higher open circuit voltage of 0.8 V than 0.5 V for SFM|LSBC|SFM fuel cells at 600 degrees C. The fuel cell with nanoBZNY infiltrated composite electrolyte achieves over double power density than cells with single LSBC and solution BZNY infiltration electrolytes at 600 degrees C that may be due to the proton conduction enhancement at lower temperature and further promotes the triple power density at 800 degrees C contributed from the oxygen ions conduction of LSBC and BZNY at high temperature. Those results provide evidence that dual ions pass through individual conduction paths in a two-phase composite electrolyte.