Galvanic replacement reaction in perovskite oxide for superior chemiresistors

Abstract

It is well known that certain gas molecules can serve as specific markers for characterizing the physiological and environmental nature of a subject, such as acetylene gas which can be used for determining a person's smoking status as well as for monitoring air pollution levels. For their reliable detection, gas sensors should be designed with high sensing capabilities in terms of selectivity, sensitivity and low detection limit. In this work, we present a rational design approach for the synthesis of p-type LaFeO₃/n-type SnO₂ composite nanotubes (NTs) via galvanic replacement reaction (GRR) on electrospun perovskite LaFeO₃ NTs for p–n type-converted sensing. The GRR process provides LaFeO₃/SnO₂ NTs with high surface area (146.6 m² g⁻¹) by generating SnO₂ nanograins (<10 nm), as controlled by varying the reaction time. The abundant heterogeneous p–n junctions formed in LaFeO₃/SnO₂ NTs contribute to the dramatic improvements in their sensing characteristics. In fact, the LaFeO₃/SnO₂ NTs exhibited 31.2-fold increased response toward acetylene (5 ppm) with a far improved response speed (16 s) compared to that of pristine LaFeO₃ NTs (64 s). Our results demonstrate that the GRR process can be used to engineer the morphology and composition of p-type perovskites to achieve exceptional chemical sensing performances.