Comparative Investigation of Electronic Leakage in Proton-Conducting Ceramics for High-Temperature Water Electrolysis

Abstract

The electronic conduction within proton-conducting ceramics represents a significant problem for the efficiency of hydrogen production through water electrolysis at high or intermediate temperatures. The doped barium-cerium-zirconate oxides, which have been successfully used for fuel cell applications, however, show electronic leakage when used in water electrolysis that ultimately lowers the Faradaic efficiency of hydrogen production. In this work, the defect chemistry of proton-conducting ceramics was used to evaluate the proton, hole, and electron conductivity from the total conductivity of BaCe0.7Zr0.1Y0.1Yb0.1O3-δ, BaCe0.4Zr0.4Y0.1Yb0.1O3-δ and BaZr0.8Y0.2O3-δ ceramics studied under different steam and oxygen partial pressures. The intrinsic electronic leakage was then related to the Ohmic potential, steam and oxygen partial pressures and temperature. The proton and electronic current densities were calculated from transport equations and then used to estimate the electronic leakage at the specified electrolysis conditions. The comparison of these three materials revealed that the rational material design and optimization of operating conditions can mitigate electronic leakage in electrolytes, which promotes the fast and efficient hydrogen production by proton-conducting solid oxide electrolysis cells.