Deciphering the Humidity Resistance and Oxygen-Content Independence of Conductometric Hydrogen Sulfide Sensors Based on Electrospun CeO2/CuO Nanotubes

Abstract

Limited by inherent physicochemical properties and surface-adsorption-dominated gas-sensing behavior, traditional metal oxides are susceptible to ambient humidity levels and oxygen content within test environments. To overcome this issue, we proposed one highly sensitive MEMS-type H₂S sensor featuring electrospun cerium oxide (CeO₂)/copper oxide (CuO) nanotubes as the sensing layer. The constituent ratio-optimized sensors (CeO₂/CuO-5) exhibited superior H₂S-sensing performance over pure CeO₂ counterparts, including lower operation temperature, more than two times stronger response (7.4 vs 3.1@4 ppm), and favorable selectivity. Density functional theory calculations and a series of characterization methods found that the increased oxygen vacancies and abundant CeO₂/CuO n-p heterojunctions jointly contributed to the promotion of receptor and transducer function. In addition, a humidity-resistant and oxygen content-independent sensor performance was demonstrated. On the one hand, the self-refreshing effect of CeO₂ endowed the CeO₂/CuO-5 sensor with 75.6% retention of response toward 4 ppm of H₂S under 70% RH with respect to the dry case, thus showcasing an excellent humidity tolerance. On the other hand, the decent oxygen storage ability of CeO₂ favored a high response even under oxygen-lean environments. Furthermore, a patrol monitor apparatus loaded with the as-prepared sensor was designed, which showed efficient detection and alerting for on-site H₂S leakage.