Effects of P-N and N-N heterostructures and band alignment on the performance of low-temperature solid oxide fuel cells

Reducing the operating temperature of solid oxide fuel cells (SOFCs) has attracted worldwide attention in recent years. This has prompted massive efforts in developing new electrolyte materials for low-temperature SOFCs, typically including heterostructure materials consisting of semiconductors and ionic conductors. In this study, a p-n heterostructure (LiZnO–SnO2) and an n-n heterostructure (ZnO–SnO2) are proposed and evaluated in SOFCs to tap further the potential of a heterostructure for low-temperature electrolyte use. The results show that the developed LiZnO–SnO2 and ZnO–SnO2 both capably play competent electrolyte roles in SOFCs with high ionic conductivities and promising fuel cell performance, achieving peak power outputs of 376 and 255 mW cm−2 at 530 °C, respectively. To interpret the good performance of the two heterostructure electrolytes, energy band alignment mechanisms based on p-n hetero-junction and n-n heterostructure are employed to illustrate the ionic enhancement and electronic suppression processes of the materials. These findings reveal new insight into developing heterostructure electrolytes for low-temperature SOFCs.