Surface reconstruction of β-Ga2O3 nanorod electrolyte for LT-SOFCs

Solid oxide fuel cell (SOFC) is a promising energy conversion technology, but the high operating temperature caused by electrolytes impedes its widespread application. The development of alternative electrolytes with fast ionic transport plays a vital role in tackling this challenge. In this study, a new electrolyte is proposed based on the wide bandgap semiconductor Ga2O3, by using a facile surface treatment on the nanorods of β-Ga2O3 in hydrogen. The treatment reconstructs the surface of the β-Ga2O3 nanorod to form a core–shell structure with an oxygen vacancy-rich shell. The nanorod sample is applied as the electrolyte in SOFC, delivering a high ionic conductivity of 0.15 S cm−1 and promising power densities of 485 mW cm−2 at 550 °C. Further studies confirm dominated proton conduction in the electrolyte and propose different mechanisms to elucidate the fast proton transport in terms of surface reconstruction. Particular attention is paid to the homo-junction at the core–shell interface by discussing the modulating effect of the junction s built-in field on proton diffusion. This work develops a new electrolyte based on β-Ga2O3 for LT-SOFC and presents an effective method of surface reductive reconstruction to enable fast proton conduction in semiconductor electrolytes.