Interface enhancement effect of hierarchical In2S3/In2O3 nanoflower heterostructures on NO2 gas sensitivity

Cocatalysts have been extensively employed to improve gas sensing performance in gas detection. However, the interface effect of the heterojunction on gas sensing has rarely been addressed. This study investigated the interface effect of constructive hierarchical In2S3/In2O3 nanoflowers on NO2 gas sensitivity using a rapid and facile microwave-assisted hydrothermal method. The structure was then modulated from In2S3, to In2S3/In2O3 heterostructures, and finally In2O3 alone by increasing the calcination time. In2S3/In2O3 heterostructures with an appropriate interface were found to significantly promote NO2 gas sensitivity with a high gas-sensing selectivity compared with pure In2S3 and In2O3. An interface enhancement model has also been developed. The strong interfacial coupling effect was key to high gas sensitivity, which likely originated from hole-electron pair separation through tuning of the interfacial electronic structure of In2S3/In2O3 nanoflowers using different calcination times. This resulted in improved charge separation efficiency and carrier collection efficiency of electrons from In2S3 to In2O3, and increased active sites. This boosted gas diffusion and adsorption, accelerated surface chemical reactions, and expedited charge transport and kinetic processes. This work provides a new approach for designing high-performance sensor using the interface effect of heterostructure nanomaterials.