Moisture-Resistant and Highly Selective NH₃ Sensor Based on CdS/WS₂ Composite Heterojunction

This study reports the synthesis of CdS/WS₂ composites via a green and ultra-low-cost hydrothermal method. By controlling the relative mass ratio between WS₂ and CdS, an n-n type CdS/WS₂ heterostructure, with excellent NH₃ gas-sensitive properties, was developed and investigated at room temperature. Compared with pristine WS₂ and CdS, the CdS/WS₂-40%wt composite exhibited excellent selectivity of more than 4 orders of magnitude for sensing NH₃, a very short recovery time of 3 s, and ultrahigh selectivity at room temperature. The large specific surface area of the CdS/WS₂ composite increased the active sites for the gas-sensitive reaction. Additionally, the 2D morphology of CdS/WS₂ and the heterojunction formed between WS₂ and CdS contributed to the improved performance. Anti-humidity interference tests showed that the CdS/WS₂ sample remained stable under real-time monitoring of NH₃ at different ambient humidity values. This study paves the way for designing high-performance gas sensors operating at room temperature.