Efficient ion conductivity enhancement mechanism induced by metal ion diffusion of SOFCs based on Fe-doped Gd₂O₃ electrolyte

Considerable efforts have been made in the past several decades to search for electrolytes that can work at low temperatures for solid oxide fuel cells (SOFCs). The rare-earth oxide Gd₂O₃ is a thermodynamically stable semiconductor material, but it has not yet been thoroughly explored for use in SOFC devices. In this study, a series of Fe-doped Gd₂O₃ with varying compositions were successfully synthesized to function as electrolytes for SOFCs. The as-prepared material, 10% Fe-doped Gd₂O₃ (Fe_0.1Gd_1.9O₃), exhibited an excellent peak power density of 1352 mW/cm² at 550 ℃, while the ionic conductivity reached 0.25 S cm⁻¹. Various spectroscopic measurements, such as X-ray photoelectron spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, and density functional theory calculations, were employed to understand the enhanced ion transportation mechanism and the improved performance of Fe-doped Gd₂O₃. The results showed that the Fe-doped Gd₂O₃ and energy bandgap tuning of electrolytes can significantly improve fuel cell performance at low temperatures, which is of great significance for the future development of low-temperature ceramic fuel cells.