Tailoring oxygen vacancy of WO₃ nanoparticles for high-performance gas sensing: room-temperature NO₂ and...

Achieving the effective room-temperature detection of gaseous pollutants has long been a sought-after yet highly challenging goal in the field of gas sensors. In this work, through calcination of H₂W₁₂O₁₁·2H₂O precursor at different temperatures, three WO₃ products with varying oxygen vacancy concentrations were prepared. Oxygen vacancies, serving as active sites, promote the adsorption of target gases, increase the carrier concentration, and modify the band gap width of WO₃. Consequently, the prepared WO₃ exhibited gas-sensing performance positively correlated with the oxygen vacancy content. Among them, the WO₃-NP-600 product with the highest oxygen vacancy concentration demonstrated an ultra-high response (703.6) and ultra-fast recovery (21 s) to 10 ppm NO₂ at room temperature, representing the highest response value and fastest recovery speed reported to date for WO₃-based sensors detecting NO₂ at room temperature. Furthermore, when the operating temperature was raised to 130 °C, the WO₃-NP-600 sensor underwent a complete switch in selectivity towards triethylamine (TEA). This transition is attributed to the fundamental difference in sensing mechanisms between oxidative NO₂ and reductive TEA gases, as well as the distinct desorption behaviors of active oxygen species on the material surface at different temperatures, as revealed by O₂-TPD, XPS and in-situ IR spectroscopy analysis. This work provide a highly viable strategy for the design and application of low-cost, low-energy- consumption, and dual-sensing gas sensors.