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 μm for the BZNY solution, and 300 μm for the nano-BZNY into a 400 μm thickness of LSBC. The infiltrated composite electrolyte exhibites lower conductivity compared to the solid-state-prepared single-phase LSBC electrolyte at 600 °C, but almost the same conductivity at 800 °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 °C. The fuel cell with nano-BZNY infiltrated composite electrolyte achieves over double power density than cells with single LSBC and solution BZNY infiltration electrolytes at 600 °C that may be due to the proton conduction enhancement at lower temperature and further promotes the triple power density at 800 °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.