Spatially Tailored Asymmetric Oxygen Vacancies Induce Nonradiative Recombination for Ultrafast and Stable NO2 Sensing

Extending the lifetime of electrons while enhancing surface activity is crucial for improving charge transfer efficiency and reaction activity in photoactivated gas sensors. However, the inherent radiative charge recombination process significantly restricts the simultaneous enhancement of both kinetic and thermodynamic performance. In this study, leveraging the differences in surface oxygen vacancy migration barriers, we precisely regulated the spatial distribution of oxygen vacancies in CeO ₂ by controlling the vacuum heat treatment temperature, successfully constructing a vertically asymmetric oxygen vacancy structure. This asymmetric configuration induces localized electric dipoles and strong electron-phonon coupling, enabling rapid transfer and highly efficient non-radiative recombination of photogenerated carriers, thereby triggering a pronounced photothermal effect. Leveraging this strategy, the CeO ₂ -based sensor sets a new benchmark for response speed, achieving an ultra-rapid and stable detection of 5 ppm NO ₂ in merely 4 s at room temperature. Our work introduces a general strategy of inducing non-radiative recombination that can be extended to photoactivated gas sensor, creating more tunability and variability in gas sensor.