Bismuth and indium co-doping strategy for developing stable and efficient barium zirconate-based proton conductors for high-performance H-SOFCs

High-temperature proton conductors gained ever-increasing interest as electrolyte materials alternative to oxygen-ion conductors due to their high conductivity associated with low activation energy at reduced temperatures. In this study, we reported our findings on chemically stable, easily sintered and highly proton-conductive BaZrO₃ oxides with Bi₂O₃ and In₂O₃ co-addition as electrolyte materials for proton conducting solid oxide fuel cells (H-SOFCs). Among the composition series, BaZr_0.75In_0.2Bi_0.05O_3−δ (BZIB5) exhibited the improved sinterability and good conductivity. Correspondingly, high-temperature gravimetry results indicated that the concentrations of protonic defect and oxygen vacancy strongly depended on P(H₂O) and temperature rather than P(O₂). Importantly, single cells with 12-μm-dense BZIB5 electrolyte films were successfully fabricated, and achieved high performance with the maximum power density of 0.34 Wcm⁻² at 700 °C. The encouraging results demonstrated that BZIB5 is a promising candidate as the electrolyte material for high performance H-SOFCs.