酸素欠損型n型混合タングステン酸化物2Dナノシートにおける非従来型ガスセンシングメカニズムと酸化タングステン(VI)との比較

Unconventional gas sensing underlies a mixed phase composition of 2D tungsten oxide nanosheets with multiple charge states, which are otherwise inaccessible, generating select catalytic surfaces. Here, we report an unconventional gas-sensing in oxygen-deficient WO_3-x. These materials are n-type phase-separated metal oxide semiconductors comprised of distinct poorly insulating WO_2.9 domains embedded in the hard insulating WO₂ host, consisting of spatially separated competing phases. Our study highlights the fundamental differences between phase-separated WO_3-x and WO₃ systems, where WO_3-x exhibits unconventional sensitivity towards NO₂ (-125% at 10 ppm) and CO (94% at 10 ppm), unlike pristine WO₃ (685% at 10 ppm NO₂ and -84% at 10 ppm CO). The WO_3-x sensor shows excellent cross-sensitivity towards NO₂ and CO, dominated by their chemisorption onto different surface(s) of 2D WO_2.9 and WO₂ nanosheets, validated by theory. The pristine WO₃ sensor exhibits high sensitivity with fast response/recovery times at room temperature, setting records among existing conventional sensors. These results suggest an unknown, possibly novel mechanism is required to explain the unconventional sensing in WO_3-x. Unconventional gas sensing, coupled with cross-sensitivity and a combination of conventional sensing across a wide temperature range, is desirable for real-world applications for sensors operating in mixed gas environments.