Tailoring the Structural Durability and Proton Conduction of Electrolytes for Highly Fuel-flexible and Reversible Ceramic Cells

Abstract

A durable and high ionic conducting electrolyte is critical for achieving fuel-flexible and reversible protonic ceramic cells (PCCs) at reduced temperatures since the developed electrolyte materials are vulnerable to steam, CO2, or coking deterioration. Here, we report a fast-conducting electrolyte material BaZr0.06Ce0.7Y0.06Yb0.06Hf0.06Gd0.06O3-δ (BZCYYbHG), demonstrating excellent durability against CO2 and H2O under the realistic electrolysis operations, and a high conductivity of 0.017 S cm-1 at 550 °C for lowering the PCC operating temperature. Density functional theory calculations indicate that the higher configurational entropy of mixing at the B-site cations slightly reduces the hydrogen adsorption energy, suggesting a higher incorporation rate of protons or hydrogen atoms into electrolyte bulk. Ultimately, single cells with BZCYYbHG electrolyte deliver peak power densities of 1.39,1.12, and 0.7 W cm-2 in H2, NH3, and CH4 at 550 °C with promising durability. In addition, the PCCs achieve a current density of -1.61 A cm-2 at 1.3 V and 550 °C with a high Faradaic efficiency of 91.3% at -0.5 A cm-2, enabling stable operations in steam electrolysis mode under humid air (30% H2O), wet air containing CO2 (up to 10%), and reversible cycling.