Sintering-induced cation displacement in protonic ceramics and way for its suppression

Protonic ceramic fuel cells with high efficiency and low emissions exhibit high potential as next-generation sustainable energy systems. However, the practical proton conductivity of protonic ceramic electrolytes is still not satisfied due to poor membrane sintering. Here, we show that the dynamic displacement of Y³⁺ adversely affects the high-temperature membrane sintering of the benchmark protonic electrolyte BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ, reducing its conductivity and stability. By introducing a molten salt approach, pre-doping of Y³⁺ into A-site is realized at reduced synthesis temperature, thus suppressing its further displacement during high-temperature sintering, consequently enhancing the membrane densification and improving the conductivity and stability. The anode-supported single cell exhibits a power density of 663 mW cm^-2 at 600 °C and long-term stability for over 2000 h with negligible performance degradation. This study sheds light on protonic membrane sintering while offering an alternative strategy for protonic ceramic fuel cells development.