Hierarchical Heterojunctions of Metal Sulfide WS₂ Nanosheets/Metal Oxide In₂O₃ Nanofibers for an Efficient Detection of Formaldehyde

The construction of transition metal dichalcogenides (TMDs) heterojunctions for high-performance gas sensors has garnered significant attention due to their capacity to operate at low temperatures. Herein, we realize two-dimensional (2D) WS₂ nanosheets in situ grown on one-dimensional (1D) In₂O₃ nanofibers to form heterostructures for formaldehyde (HCHO) gas sensors. Capitalizing on the p-n heterojunctions formed between WS₂ and In₂O₃, coupled with the high surface-to-volume ratio characteristic of 1D nanostructures, the WS₂/In₂O₃ NFs sensor demonstrated an elevated gas response of 12.6 toward 100 ppm HCHO at 140 °C, surpassing the performance of the pristine In₂O₃ sensor by a factor of two. Meanwhile, the sensor presents remarkable repeatability, rapid response/recovery speed, and good long-term stability. The superior sensing capabilities of WS₂/In₂O₃ NFs heterojunction are attributed to the combined impact of the increased charge transfer and the presence of more sites for gas adsorption. The research endows a potent approach for fabricating TMD heterojunctions to significantly enhance the gas sensing properties of gas sensors at relatively low temperatures.