Enhancing proton conductivity and stability in Sn-doped Ba3(BaTa2)O9 for low-temperature solid oxide fuel cells

In the development of proton-conducting fuel cells, improving the proton conductivity and chemical stability of electrolytes is crucial. Ba4Ta2O9-based proton conductors represent a novel class of composite perovskite proton conductors. Elemental doping is expected to enhance the electrical properties of Ba4Ta2O9, which offers valuable insights for exploring higher-performance proton-conducting materials. This study investigates the effects of Sn and Ba doping on the proton conductivity, chemical stability, and electrochemical performance of Ba4Ta2O9. Ba3(BaSn0.3Ta1.7)O9−δ (BSnT30) and Ba3(BaBa0.3Ta1.7)O9−δ (BBaT30) are successfully synthesized via the solid-state reaction method. Among them, Sn doping effectively improves the chemical stability of Ba4Ta2O9 and endows it with higher proton conductivity under a humid H2 atmosphere in the temperature range of 400–650 °C. Defect equilibrium model analysis and hydrogen concentration cell experiments demonstrate that BSnT30 exhibits a higher proton transport number. Specifically, under a typical H2/air atmosphere, BSnT30 achieves a peak power density of 1088 mW cm−2 at 550 °C, which represents an increase of 162 % compared with that of BBaT30. Distinct from conventional ABO3-type proton conductors, Sn doping in the complex perovskite Ba4Ta2O9 simultaneously enhances chemical stability and proton transport, avoiding the typical conductivity–stability trade-off. This study provides a rational doping strategy to obtain composite perovskite proton conductors with high proton conductivity and excellent chemical stability, enabling efficient and sustainable energy conversion in low-temperature solid oxide fuel cell technology.