High-Performance Sr and Mg Co-Doped LaAlO3 Proton Conducting Electrolyte for Semiconductor Ion Fuel Cells

A major challenge for semiconductor ion fuel cells (SIFCs) is to design an electrolyte with proton transport properties so that it can maintain high ionic conductivity within relatively low temperatures. Herein, we develop a Sr and Mg codoped LaAlO₃ electrolyte that facilitates efficient conduction of protons and oxygen ions by enriching oxygen vacancies and reducing the activation energy of ion conduction. The optimized electrolyte shows a low activation energy of 0.31 eV and demonstrates remarkably elevated ionic conductivity at low temperatures, e.g., 0.1994 S cm^–1 at 550 °C. This is attributed to the significant increase in oxygen vacancies, which has been verified by XPS technology. Meanwhile, the Sr and Mg codoped LaAlO₃ electrolyte exhibits remarkable proton transport properties, confirmed by proton filtration experiments, which provide further evidence for the improvement of the electrolyte ionic conductivity. As a result, the fuel cell with an optimized LaAlO₃ electrolyte delivers an impressive peak power density of 977 mW·cm^–2 with an open circuit voltage (OCV) of 1.126 V at 550 °C. Particularly, compared with the fuel cell with a pure LaAlO₃ electrolyte, the peak power density is increased by 38.4%. The dual-ion doping strategy provides crucial insight into the further development of high ionic conductivity electrolytes for SIFCs.