Towards highly dense electrolytes at lower sintering temperature (∼1200 °C): Optimization strategies for BaCe0.7Zr0.1CuxY0.2-xO3-δ in SOFCs.

High-conducting and long-term stable proton-conducting electrolytes are of utmost importance. This study investigates the synthesis and characterization of BaCe 0.7 Zr 0.1 Cu x Y 0.2-x O 3-δ (BCZCu x Y; x = 0, 0.005, 0.01, 0.02, 0.05, and 0.1) electrolytes tailored for proton-conducting solid oxide fuel cells (SOFCs). Through Cu2+ doping at the B-site of BaCe 0.7 Zr 0.1 Y 0.2 O 3-δ (BCZY), a successful reduction of the sintering temperature to 1200 °C was achieved. BCZCu 0.02 Y exhibited a high relative density of approx. 98.1% at this temperature, but beyond 2 mol% Cu doping, the appearance of a BaCuO 2 secondary phase adversely impacted conductivity. The electronic properties of BCZY and BCZCu x Y are elucidated via partial density of states (PDOS) analysis, revealing optimized crystal structures and band gap reductions (from approx. 1.9 eV–1.1 eV) upon Cu doping. Notably, BCZCu 0.02 Y demonstrated a commendable conductivity, with values of 3.5 × 10−2 S. cm−1 in air and 4.8 × 10−2 S. cm−1 in a moist atmosphere at 750 °C. Remarkably, excellent electrochemical stability was observed in a moist hydrogen atmosphere for up to 450 h at 600 °C. Single cells incorporating BCZCu 0.02 Y electrolytes exhibited peak power densities of 380 mW/cm2 at 750 °C. The incorporation of 2 mol% Cu2+ in the BCZY lattice holds promise for achieving low-temperature sintering and high-performance proton-conducting SOFCs. [ABSTRACT FROM AUTHOR]