Synergistic effect of sodium content for tuning Sm2O3 as a stable electrolyte in proton ceramic fuel cells

Samarium oxide (Sm 2 O 3 ), a rare earth sesquioxide, shows that a great potential in proton-conducting fuel cells. However, the stability of Sm 2 O 3 based cell remains a challenge. Herein we reported a facile method for enhancing the stability via the incorporation of sodium content into Sm 2 O 3 . This study discloses that the existence of sodium induces phase transition of Sm 2 O 3 from monoclinic to cubic phase beneficial for fast proton transportation. Further mechanism investigation reveals that the cubic phase structure of Sm 2 O 3 is stabilized resulting from substitution of sodium. Compared with commercial Sm 2 O 3 (CSM), the fuel cell employing Na–Sm 2 O 3 (NSM) as electrolyte delivers an improved peak power density of 570 mW cm −2 and the extended stability over 100 h under 130 mWcm −2 at 520 °C. In this study, NSM is successfully developed as a stable electrolyte material for proton conduct fuel cells, expanding its application in electrochemical devices.