Hierarchical Porous CdS–Co₃O₄ Heterostructures for H₂S Gas Sensing at Room Temperature

This paper reports a liquid-borne ultrasound-assisted pretreatment method for preparing a CdS–Co3O4 nanohybrid with high specific surface area and hierarchical porous structure via a hydrothermal synthesis method. In this work, the CdS NPs are uniformly dispersed within the framework of nanoflower spherical Co3O4 nanomaterials under the effect of acoustic cavitation, forming a stable heterojunction structure with Co3O4. The results indicate that the microstructure of the CdS–Co3O4 nanohybrid can be regulated by adjusting the ultrasonic parameters. The fabricated CdS–Co3O4-based gas sensor has an ultralow H2S concentration detection limit (0.2 ppm) at room temperature. After 3000 bending–unbending cycles at a bending angle of approximately 45° and 0.5 Hz frequency, the sensing response decreases about 3.26% and 6.43% for 5 and 50 ppm of H2S gas, respectively. Additionally, experiments on the freshness detection of different food using the fabricated sensor demonstrate its potential for practical applications.