Boosting Bulk-to-Surface Electron Transfer in CeO₂ via Oxygen Vacancy Channels for Ultrafast NO₂ Sensing

Modulating the electron transport dynamics in gas sensors is crucial for achieving rapid-response gas detection. However, polaron localization causes sluggish electron migration from the bulk to the surface, severely limiting surface electron concentration and reaction activity. In this work, we leverage the difference in migration barriers of surface V_o in CeO₂ to drive the directional migration of surface V_o into the bulk via precisely controlled thermal treatment, thereby forming electron transfer channels bridging the bulk and the surface. Experiment result confirm that the formation of electron channels enhances electron transfer efficiency from bulk to surface, leading to a dual improvement in both electron concentration and reaction activity at surface V_o sites, which further promotes the adsorption and activation of O₂ and NO₂. Enabled by this strategy, CeO₂ achieves long-term stability and new benchmark for ultra-fast detection of 20 ppb NO₂ in 5 s at room temperature. This work provides a new strategy to resolve the kinetic contradiction between bulk electron transport and surface reactions.