Lowering the Temperature of Solid Oxide Electrochemical Cells Using Triple‐Doped Bismuth Oxides

Abstract Despite the great potential of solid oxide electrochemical cells (SOCs) as highly efficient energy conversion devices, the undesirable high operating temperature limits their wider applicability. Herein, a novel approach to developing high‐performance low‐temperature SOCs (LT‐SOCs) is presented through the use of an Er, Y, and Zr triple‐doped bismuth oxide (EYZB). This study demonstrates that EYZB exhibits > 147 times higher ionic conductivity of 0.44 S cm⁻¹ at 600 °C compared to commercial Y‐stabilized zirconia electrolyte with excellent stability over 1000 h. By rationally incorporating EYZB in composite electrodes and bilayer electrolytes, the zirconia‐based electrolyte LT‐SOC achieves the unprecedentedly high performance of 3.45 and 2.02 W cm⁻² in the fuel cell mode and 2.08 and 0.95 A cm⁻² in the electrolysis cell mode at 700 °C and 600 °C, respectively. Further, a distinctive microstructural feature of EYZB that largely extends triple phase boundary at the interface is revealed through digital twinning. This work provides insights for developing high‐performance LT‐SOCs.