Thermally activated electric-field relay for ultra-fast and stable NO2 detection over wide temperature range

Conventional metal oxide sensors often suffer from limited long-term stability over an ultrabroad temperature range, primarily due to their single-type active sites and a static electronic configuration. To overcome this limitation, we constructed a dual local electric field (LEF) with a graded electron concentration profile by precisely modulating the local chemical environment of CeO₂. This design introduces a thermally activated electric-field switching mechanism, which enables ultrafast and stable response value toward NO₂ detection from -50 to 800 °C. We demonstrate that at low temperatures, the divergent hybridization between Pt and Ce orbitals leads to a lower thermal activation energy for LEF-1 than for LEF-2. As temperature rises, electron migration from the 4f orbitals of Ce³⁺ to adjacent Ce⁴⁺ weakens LEF-1, whereas thermal activation promotes efficient electron transfer in LEF-2, allowing LEF-2 to dominate at high temperatures and ensuring continuous activity. This relay sensing mechanism sustains rapid response (within 12 s) and long-term stability (over 75 d) at both -50 and 800 °C. This work presents an adaptive sensing mechanism through electron gradient differentiation and thermal-driven field switching, offering a new paradigm for the design of intelligent sensors under extreme conditions.