Tuning La₂O₃ to high ionic conductivity by Ni-doping

Ni-doped La₂O₃ was developed as an ionic conducting membrane corresponding to a conductivity of 0.187 S cm^-1 at 550 °C. A peak power density of 970 mW cm^-2 with an open circuit voltage of 1.05 V was achieved using 10 mol% Ni-doped La₂O₃ (10NLO). XPS and Raman investigations reveal that the performance enhancement is due to the high concentration of oxygen vacancies. Density functional theory calculations verify that Ni doping can tune the band structure of La₂O₃ to enhance its electrochemical performance. A Schottky junction barrier is formed at the anode to avoid short circuit problems and facilitate the ionic transportation at the anode/electrolyte interface. This study indicates that wide-band gap semiconductors with suitable element-doping can be tuned to be promising ionic conductors for advanced fuel cell applications.