Highly functional molten sodium hydroxide-BaZrO3 composite electrolyte with hybrid ionic conductivity for low-temperature solid oxide fuel cells

Abstract

Proton-conducting barium zirconate perovskite attracts considerable attention as an electrolyte for solid oxide fuel cells (SOFCs). To obtain BaZrO3-based electrolytes with high ionic conductivity at low temperatures, composite electrolytes named BaZrO3+x wt% NaOH are designed and synthesized. A study is conducted to explore the effects of molten-state NaOH and a small amount of Na2CO3 generated during SOFC operation on the performance of composite electrolytes systematically. As a result of the addition of NaOH, the composite electrolyte is created with rich surfaces and solid-liquid interfaces, compared to traditional condensed electrolytes.The solid-liquid interface can serve as a high-speed ion conduction channel. In-situ surface oxygen deficiency induced by NaOH and the bridge function of carbonate enable rapid ion migration along the interface of the composite electrolyte. The fuel cell with the prepared electrolyte can deliver an excellent maximum power density (MPD) of 1039 mW cm-2 at 550 °C. At 350 °C, the cells are also able to show a very impressive power density of 365 mW cm-2. The concise design, convenient preparation process, and outstanding performance of the fuel cell collectively offer an effective strategy for advancing the manufacture of electrolyte materials for low-temperature operation.