<i>In Situ</i> Generatable and Recyclable Oxygen Vacancy-Modified Fe₂O₃-Decorated WO₃ Nanowires with Super Stability for ppb-Level H₂S Sensing

Detecting hydrogen sulfide (H 2 S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO 4 2– deposition. To address this issue, we developed a sensing material comprising Fe 2 O 3 -decorated WO 3 nanowires (FWO) with strong interfacial interaction. During the H 2 S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe 2 O 3 cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H 2 S at 250 °C, with an experimentally measured detection limit of 1 ppb. It also exhibits remarkable stability, with no significant change observed over a long period of 150 days. Based on a combination of in situ DRIFT and DFT calculations, we have identified that the overactivation of O 2 is the key step in the formation of SO 4 2– . This overactivation can be partially modulated by the synergistic effect of Fe 2 O 3 decoration and the in situ generated OVs, regulating the oxidation product to SO 2 rather than the toxic SO 4 2– . Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO 4 2– deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H 2 S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.