Interfacial active-sites p-n heterojunction SFT-WO₃ for enhanced fuel cell performance at 400–500 °C

The enhanced ionic conductivity of electrolytes in fuel cells could be optimized by inhibiting the e-conduction, constructing heterostructure, built-in electric field (BIEF), and creating a more active site within the lattice. High ionic conductivity and suppression of e-conductivity are of paramount significance in the field of a fuel cell. One possible approach is synthesizing the type-II heterojunction to achieve high ionic conductivity and enhanced fuel cell performance. In this perspective, we have synthesized p-n heterojunction SFT (SrFe_0.3Ti_0.8O₃)-WO₃ via compositing the individual SFT (p-type) and WO₃ (n-type) semiconductors. The obtained SFT-WO₃ exhibit impressive fuel cell performance of 875 mW/cm², high ionic conductivity of 0.2 S/cm, and better OCV 1.04 V at a low operating temperature of 520 °C. The excellent fuel cell performance and high ionic conductivity can be interpreted as the synergistic effect between SFT-WO₃ heterojunction and BIEF. Various characterizations (XRD, SEM, HR-TEM, UV–visible, UPS, and XPS) confirmed heterojunction formation between SFT and WO₃. Furthermore, the energy band structure and valence band deviation of the SFT-WO₃ junction were approved. Also, the theoretical calculation (DFT calculation) has been performed to support the experimental results. Our finding reveals that the synthesized heterostructure SFT-WO₃ is a competent and promising electrolyte indicating the insight of developing low-temperature-based electrolytes for fuel cell technology.