Band-Engineering W18O49 with Cu Single Atoms Enables Efficient Photo-Induction of Oxygen Radicals for Highly Sensitive Room-Temperature NO2 Detection

Abstract Metal oxide semiconductor gas sensors suffer from insufficient sensitivity and slow response/recovery due to inefficient charge separation and sluggish surface reaction kinetics at room temperature. Herein, we demonstrated that single-atom Cu doping enabled precise band structure engineering of W18O49, thereby enabling photoassisted room-temperature NO2 detection with high sensitivity and selectivity. Single-atom Cu induced abundant oxygen vacancies and regulated the electronic configuration, facilitating oxygen radical generation and interfacial charge transfer. Consequently, the Cu1–W18O49 sensor exhibited a high response (RNO2/Rair = 572.3) toward 10 ppm of NO2 and excellent selectivity under light. In situ Fourier transform infrared spectroscopy confirmed the formation of multiple nitrogen oxide species on the Cu1–W18O49 surface and revealed that the Cu doping induces a transformation of the NO3 adsorption configuration from a weak monodentate to a bidentate binding mode, highlighting the enhanced surface reactivity by Cu doping. This work provides fundamental insights into the rational design of high-performance photoactivated gas sensors.