Enhancing protonic ceramic electrolysis cell performance through electrolyte composition optimization

Polarization resistance, chemical stability against high steam, and faradaic efficiency (FE) are important parameters for steam electrolysis using protonic ceramic electrolysis cells (PCEC) at an intermediate temperature range of approximately 500 °C. To investigate the effects of electrolyte composition on these parameters, PCECs were fabricated using two electrolyte compositions: one without Zr, Ba(Ce0.8Y0.1Yb0.1)O3-δ (BCYYb), and one with Zr, Ba(Ce0.3Zr0.5Y0.1Yb0.1)O3-δ (BCZYYb), as well as a double-layered electrolyte BCYYb/BCZYYb. Although Zr in BCZYYb is required for chemical stability, BCYYb without Zr can also be chemically stable against high steam at 500 °C. Additionally, BCYYb has a higher conductivity compared to BCZYYb, which contributes to lower ohmic resistance and the highest peak power density in H2 fuel at 700 °C (2.04 W/cm2) among the cells with three different electrolytes. However, the BCYYb electrolyte exhibits a slightly higher polarization resistance than BCZYYb. In PCEC operation at 500 °C, the electrolyte composition significantly affects the FE. At a high current density (0.8 A/cm2), the FE of the PCEC with the BCYYb electrolyte (85%) is significantly larger than that with BCZYYb (68%).