Electrospun ZnO Nanotubes Decorated with Zinc Ferrite Nanoparticles as Sensing Material for Hydrogen Sulfide Detection

Coaxial electrospinning is first employed for loading zinc ferrite (ZnFe 2 O 4 ) nanoparticles onto zinc oxide (ZnO) nanotubes for sensing hydroxide sulfite (H 2 S) in the gaseous phase. The obtained ZnFe 2 O 4 /ZnO composite consists of protruding ZnFe 2 O 4 nanoparticle-decorated inner ZnO nanotubes, forming a unique double-layer core–shell structure with a large amount of p–n heterojunction interfaces and oxygen vacancy defects. The nanotubes have a diameter range from 47 to 88 nm and a wall thickness range from 17 to 46 nm. The ZnFe 2 O 4 /ZnO sensors demonstrate enhanced sensitivity, selectivity, and fast response to H 2 S gas compared to the ZnO nanowire sensor, particularly at lower operating temperatures (50–240 °C). With the molar ratio of zinc nitrate to iron nitrate at 7:3, the derived ZnFe 2 O 4 /ZnO sensor had maximal responses of 3.3–98.5 to H 2 S at 0.1–10 ppm under the optimal temperature of 130 °C, significantly higher than that of the ZnO nanowire sensor. The significant enhancement in H 2 S-sensing is attributed to the synergistic effect between the ZnFe 2 O 4 and ZnO species and the presence of abundant oxygen vacancies. This research suggests exploiting high-performance H 2 S-sensing materials based on coaxial electrospinning.