Research on the construction and gas sensitivity mechanism of cerium oxide/cadmium sulfide ammonia gas sensor with multiple surface defect states induced by heterojunction

In this study, a high-performance ammonia (NH 3 ) gas sensor based on a CeO 2 /CdS heterojunction with increased surface defects was prepared using the hydrothermal method. First-principles calculations based on density functional theory (DFT) were employed to elucidate the sensing mechanism. Experimental results indicate that   more surface defects and surface hydroxyl groups can effectively enhance the performance of the CeO 2 /CdS NH 3 gas sensor at room temperature.   The response value of CeO 2 /CdS is 739.5 at a concentration of 500 ppm NH 3 , and the response/recovery time at 50 ppm is 1.27 s/1.63 s, which is faster   compared with the previously reported NH 3 gas sensors based on CeO 2 . Theoretical calculations suggest that the presence of more oxygen vacancies or sulfur vacancies on the surface of CeO 2 or CdS can lead to the generation of additional d electrons   and the capture of more NH 3 molecules. Furthermore, it was discovered for the first time that the d-band center of CeO 2 could shift upward   under   more surface oxygen vacancies and hydroxyl groups, which can improve the chemical activity of the CeO 2 /CdS and enhance its adsorption capacity for NH 3 molecules.   This research constructed CeO 2 /CdS with multiple surface defects through a heterogeneous structure, providing new ideas for developing high-performance NH 3 gas sensors.