Semiconductor Heterostructure (SFT-SnO₂) Electrolyte with Enhanced Ionic Conduction for Ceramic Fuel Cells

Electronic conduction inhibition, heterostructure construction, constituting built-in electric field (BIEF), and the generation of an energetically more active region in the lattice and at the interface are ways to increase the ionic conductivity (σ_i) of electrolyte materials for ceramic fuel cells (CFCs). The conduction of ions and stoppage of e^- conductivity are of utmost importance in semiconductor-based electrolytes. Type-II heterojunction can be synthesized to improve fuel cell performance by increasing ionic conductivity. SFT (SrFe_0.3Ti_0.7O₃)-SnO₂ p-n heterojunction was produced by combining p-type SFT and n-type SnO₂ semiconductors. The resulting SFT-SnO₂ heterostructure unveiled a high ionic conductivity of 0.18 S/cm and an open-circuit voltage (OCV) of 1.04 V, contributing to a remarkable power output of 805 mW/cm² at a low operating temperature of 520 °C. High ionic conductivity and efficient fuel cell performance are attributed to a synergistic interaction between the SFT/SnO₂ heterojunction and BIEF. Heterojunction production between SFT and SnO₂ was confirmed by numerous characterization techniques (X-ray diffractometer (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV-visible, ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS)). The SFT/SnO₂ junction valence band deviation and energy band structure were also validated. Our research shows that the constructed heterostructure SFT-SnO₂ is an effective and efficient electrolyte material for future fuel cell technology.