Pre-reacted approach for enhanced electrolyte densification in proton-conducting solid oxide electrolysis cells

The electrolyte membrane plays a central role in determining the electrochemical performance of proton-conducting solid oxide electrolysis cells (H-SOECs). However, obtaining dense membranes with high proton conductivity remains challenging because widely used barium cerate–zirconate perovskite oxides exhibit low sintering activity and typically require high processing temperatures. Here, a pre-reacted powder approach is proposed to enhance electrolyte densification while preserving high conductivity. Powders synthesized directly in the perovskite phase with a compact particle structure achieve full densification at a shrinkage of 13%, whereas conventionally processed precursors remain porous even at 17% shrinkage. The strategy is effective for both BaCe 0.7 Zr 0.1 Y 0.2 O 3−δ (BCZY) and BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3−δ (BCZYYb) electrolytes, resulting in conductivity increases of approximately 150% and 60%, respectively. The improvement arises from enhanced bulk transport and reduced grain boundary resistance. When combined with a shrinkage-assisted support design, thin electrolyte membranes can be densified at 1400 °C, lower than conventional sintering temperatures. The resulting H-SOEC single cells exhibit 20-50% higher current density, and resistance contributions are analyzed by electrochemical impedance spectroscopy. This reduced-shrinkage densification strategy provides a scalable route for high-quality proton-conducting electrolytes and offers potential applicability to other ceramic membrane systems.