Electrochemical Properties of a Dual-Ion Semiconductor-Ionic Co0.2Zn0.8O-Sm0.20Ce0.80O2-δ Composite for a High-Performance Low-Temperature Solid Oxide Fuel Cell

Semiconductor heterostructures offer a high ionic conduction path enhanced by built-in electric field at the interface, which helps to avoid electronic conduction in low-temperature solid oxide fuel cells (LT-SOFCs). In this study, we synthesized a semiconductor heterostructure based on Co-doped ZnO and Sm0.2Ce0.8O2-delta (SDC) for LT-SOFC application. First, we optimized the composition of the Co-doped ZnO by varying the doping concentration. The cell with Co0.2Zn0.8O composition (sigma(i) =0.158 S cm(-1)) yielded the best performance of 664 mW cm(-2) at 550 degrees C. This optimized composition of Co-doped ZnO was mixed with a well-known ionic conductor Sm0.2Ce0.8O2-delta (SDC) to further improve the ionic conductivity and performance of the cell. The heterostructure formed between these two semiconductor materials improved the ionic conductivity of this composite material to 0.24 S cm(-1) at 550 degrees C, which is 2 orders higher in magnitude than that of bulk SDC. The fuel cells fabricated with this promising semiconductor-ionic heterostructure material produced an outstanding power density of 928 mW cm(-2) at 550 degrees C. Our further investigation shows protonic conduction (H+) in the Co0.2Zn0.8O-SDC composite, which exhibited protonic conduction 0.088 S cm(-1) with a power density of 388 mW cm(-2). at 550 degrees C. A detailed characterization of the material and the fuel cells is performed with the help of different electrochemical (electrochemical impedance spectroscopy (EIS)), spectroscopic (X-ray diffraction (XRD), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS)), and microscopic techniques (scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectrometry (EDX)). The stability of the cell was tested for 35 h to ensure stable operation of these devices. This semiconductor-ionic heterostructure composite provides insight into the development of electrolyte membranes for advanced SOFCs.