Silicon-doped BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ electrolyte with high mechanical strength and electrical performance for protonic ceramic cells

Protonic ceramic cells (PCCs) are recognized as a promising energy conversion technology for green hydrogen and electricity production owing to their high efficiency, all-solid-state structure, and exceptional reversibility. However, the inadequate mechanical strength of proton-conducting electrolytes remains a critical challenge hindering the widespread application of PCCs. In this study, a cation regulation strategy is employed to enhance the electrolyte mechanical strength by doping silicon (Si) at the B-site of the conventional proton-conducting material BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ (BZCYYb). The optimized Ba(Zr_0.1Ce_0.7Y_0.1Yb_0.1)_0.99Si_0.01O_3−δ (BZCYYbSi) demonstrates significantly improved grain boundary conductivity, structural stability, and mechanical strength, achieving a hardness of 3.11 GPa—1.5 times greater than that of pristine BZCYYb (1.14 GPa). The PCC incorporating a thin-film BZCYYbSi electrolyte exhibits a peak power density of 1.179 W cm⁻² at 600 °C in fuel cell mode and an electrolysis current density of 1.591 A cm⁻² at 1.3 V/600 °C, outperforming the BZCYYb-based counterpart (0.994 W cm⁻² and 1.244 A cm⁻²). Additionally, the BZCYYbSi-based PCC maintains a stable operation for over 370 h at 550 °C in a continuous discharge and electrolysis situation. This work provides new insights for the design and fabrication of mechanically strengthened and high-performance electrolytes for low-temperature PCCs.