Characterizing the Blocking Electron Ability of the Schottky Junction in SnO₂–SDC Semiconductor–Ionic Membrane Fuel Cells

Recent research has shown that fuel cells using semiconductor–ionic conductor material (SIM) as electrolytes can achieve good performance due to the enhancement of ionic conductivity, and the Schottky junction is expected to block the electron conduction to further address the shorting circuit issue, but efficient characterization of the blocking electron ability of the Schottky junction is absent. In this work, SnO₂-Ce_0.8Sm_0.2O_2−δ(SDC) SIM was applied as an electrolyte membrane to assemble the semiconductor–ionic membrane fuel cell (SIMFC). Although the SnO₂-SDC SIM electrolyte possessed certain electron conduction, such a device can also deliver an open circuit voltage above 1 V, and the maximum output power reached 1059 W cm^–2 at 550 °C without a shorting circuit problem. The rectifying curve was recorded under an inset gas atmosphere to evaluate the blocking electron ability of the Schottky junction. The UPS and UV–vis characterization revealed that the band energy alignment of the Schottky junction is the underlying reason for eliminating electron conduction in SIMFC, and the blocking electron capability is related to the barrier energy of the Schottky junction, which is determined by the difference between the work function of the metal and the Fermi level of the semiconductor. The characterization of band energy and rectifying curve provides a common methodology for SIMFC.