High-Performance NO2 Gas Sensing via W6+-Doped ZnO Ultrathin Nanosheets through Morphological Control and Oxygen-Vacancy Synergy

Doping with transition metal ions is an effective way to significantly enhance the performance of MOS-based gas sensors. Conventional doping strategies often lack control over morphological evolution and fail to elucidate the complex interactions between dopants and intrinsic defects. Herein, we demonstrated a rational defect-engineering approach by introducing W 6+ dopants into morphology-prefabricated layered ZnO hexagonal prisms, which triggered a controlled transformation into ultrathin nanosheets (15-20 nm thickness) while systematically changing oxygen vacancy and zinc vacancy concentrations. The concentration changes of intrinsic defect, as well as the formation energy, were confirmed through various characterization methods and DFT calculations. The gas sensitivity test results showed that the response has been significantly enhanced after doping W 6+ , which can reach 64 to 1 ppm of NO 2 , and the detection limit was as low as 200 ppb. At the same time, it has excellent stability and selectivity. Finally, the gas-sensing mechanism thoroughly explored the charge balance process caused by W 6+ doping, the functions of oxygen vacancy and zinc vacancy, and the NO 2 sensitization mechanism.