Transition Metal-Engineered Oxygen Vacancy-Mediated Al-Doped WO₃ Nanoplates for NO₂ Detection

The pursuit of exceptional performance stands as a perpetual focus in gas sensor research. Given the intricacies of response and recovery processes, achieving selectivity, high response, and swift response/recovery time remains a challenging endeavor in the atmospheric environment. Chemiresistive metal oxide semiconductor gas sensors find extensive use, operating effectively at moderate temperatures, for detecting toxic gases such as nitrogen dioxide (NO2). The gas-sensing performance of pristine and Al-doped tungsten trioxide (WO3) has been comprehensively examined, and the findings demonstrate that an NO2 sensor based on hierarchical nanoplates exhibits an impressive and well-rounded gas sensitivity performance profile. This includes a low limit of detection of 4.7 ppm, a broad detection range spanning from 2.5 to 10 ppm (with a sensing performance of 9683%), exceptional selectivity, rapid response and recovery characteristics of 17 s/72 s for an AW3 sensor, outstanding repeatability, as well as better long-term stability. The remarkable gas-sensing performance can be attributed to the presence of defects in the oxygen vacancy structure. This effectively enhances the surface reactivity of monoclinic WO3 nanoplates, contributing to their high sensitivity and broad-range sensing performance. Consequently, this study showcases significant potential for the application of environmental NO2 monitoring.