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

Detecting hydrogen sulfide (H₂S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO₄^2– deposition. To address this issue, we developed a sensing material comprising Fe₂O₃-decorated WO₃ nanowires (FWO) with strong interfacial interaction. During the H₂S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe₂O₃ cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H₂S 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 O₂ is the key step in the formation of SO₄^2–. This overactivation can be partially modulated by the synergistic effect of Fe₂O₃ decoration and the in situ generated OVs, regulating the oxidation product to SO₂ rather than the toxic SO₄^2–. Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO₄^2– deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H₂S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.