Synergistic multielement effect at the B-site of high entropy double perovskite oxide: A promising fuel electrode for efficient co-electrolysis of H2O and CO2

• A novel high-entropy perovskite SFTCMMC is proposed as a fuel electrode for SOEC, demonstrating superior co-electrolysis performance. • The SOEC achieves a high current density of 1.47 A·cm−2 at 850°C and 1.5 V during H2O/CO2 co-electrolysis. • The cell exhibits excellent long-term stability over 150 hours at 1.3 V with no carbon deposition, addressing durability issues of conventional Ni-based electrodes. • The synergistic multielement effect at the B-site enhances catalytic activity and stability, offering a promising alternative for efficient and stable co-electrolysis.