Strategy for improving the low-temperature moisture resistance of H₂S sensors and its sensing mechanism

The severe impact of humidity on low-temperature sensing performance has long been an urgent issue to be addressed in the field of semiconductor gas sensors. In many scenarios, such as breath analysis, sewers, swamps and mines, H₂S coexists with a large amount of water vapor, making it particularly necessary to improve its low-temperature moisture resistance. In this paper, A HEA was fabricated and employed to improve the low-temperature moisture resistance of SnO₂-based H₂S sensors. The results show that 1.5 wt% HEA modified SnO₂ exhibits the best sensitization performance toward H₂S gas sensor, and excellent moisture resistance at low temperatures. At high relative humidity (RH = 80%), a response of 15 was maintained with no decline over the 7-day test period. At the same time, it can also enhance the H₂S (0.5 ppm) response on SnO₂ from 1.2 to 22, lower the response time from 30 s to 4 s, the recovery time from 140 s to 101 s, and decrease the limit of detection (LOD) down to 41 ppb at 70 °C. Theoretical calculations show that HEA can enhance the competitive adsorption of oxygen to water, thereby increasing the concentration of reactive oxygen species (ROS). Additionally, the electron transfer from HEA to SnO₂ can jointly regulate the energy-to-structure and carrier concentration of SnO₂, promoting the adsorption of oxygen and the reaction with H₂S. This study offers a new strategy for improving the low-temperature performance of gas sensors under high-humidity environments.