Intermediate-Temperature Solid Oxide Fuel Cells Based on Heterostructure p-Type Sr₂Nb_1.9Ti_0.1O_7–δ Microplates and n-Type ZnO Nanoparticles

The development of heterostructure electrolytes represents a promising strategy for enhancing the performance of solid oxide fuel cells for the intermediate-temperature solid oxide fuel cell (IT-SOFC). In this work, a p–n semiconductor ZnO-SNT heterostructured electrolyte based on p-type Sr 2 Nb 1.9 Ti 0.1 O 7 –δ (SNT) and n-type ZnO nanoparticles is proposed. In addition, its structural characterization and electrochemical performance are also investigated. Particular attention is paid to the effect of the commercial ZnO particle size on the electrical conductivity. It was revealed that the resulting ZnO-SNT electrolyte exhibited a desirable heterostructure and was enriched with oxygen vacancies. Electrochemical studies demonstrated that the 6ZnO-4SNT fuel cell achieved a peak power density of 570 mW cm –2 at 550 °C, with an open-circuit voltage of 1.06 V, and an ionic conductivity of 0.163 S cm –1 . Meanwhile, such optimal cell performance was yielded at an average size of 30 nm for the ZnO, which indicated that the interfacial area plays a crucial role in the ionic conductivity of the ZnO-SNT composites. Further investigation of the rectification properties showed that there was a pronounced p–n rectification effect in the ZnO-SNT heterostructure. Building upon this finding, the band alignment effect was exploited to explain the electron-blocking and ion-promoting behavior of such p–n heterojunctions. Our findings not only show that ZnO-SNT nanocomposites are promising electrolytes but also provide insights into the development of effective IT-SOFC electrolytes utilizing semiconductor heterostructure materials.