The "screening behavior" of lithium: Boosting H₂S selectivity of WO₃ nanofibers

An ideal way to boost the selectivity of sensing materials is that improving the sensitivity of the target gas while suppressing that of other interfering ones. Here, the "screening behavior" of the Li doped WO₃ nanofibers (Li/WO₃ NFs) have been discovered in suppressing the response from interfering gases, while elevating the H₂S sensing response. Beneficially, the H₂S response of Li/WO₃ NFs sensor prototype is three times (R_a / R_g = 64@10 ppm) as high as that of the pristine WO₃ ones (R_a / R_g = 21@10 ppm) at ~75% relative humidity and 260 °C. Moreover, Li/WO₃ NFs sensor prototype presents the detection limit as low as 100 ppb. Particularly, the Li/WO₃ NFs sensors detect simulated halitosis breath, of which the accuracy is comparable with gas chromatography. Theoretically, the decrease of the responses of Li/WO₃ NFs to interfering gases is ascribed to the enhancement of the adsorption of water molecules by Li dopant. While the improved response to H₂S is attributed to stronger adsorption of H₂S and WO₃ and to the increased defect oxygen. The "screening behavior" of Li doped into WO₃ NFs provides a new strategy that might improve the selectivity of other gas sensing.