Tandem Electric-Fields Prolong Energetic Hot Electrons Lifetime for Ultra-Fast and Stable NO₂ Detection

Prolonging energetic hot electrons lifetimes and surface activity in the reactive site can overcome the slow kinetics and unfavorable thermodynamics of photo-activated gas sensors. However, bulk and surface recombination limit the simultaneous optimization of both kinetics and thermodynamics. Here tandem electric fields are deployed at (111)/(100)Au-CeO₂ to ensure a sufficient driving force for carrier transfer and elucidate the mechanism of the relationship between charge transport and gas-sensing performance. The asymmetric structure of the (111)/(100)CeO₂ facet junction provides interior electric fields, which facilitates electron transfer from the (100)face to the (111)face. This separation of reduction and oxidation reaction sites across different crystal faces helps inhibit surface recombination. The increased electron concentration at the (111)face intensifies the interface electric field, which promotes electron transfer to the Au site. The local electric field generated by the surface plasmon resonance effect promotes the generation of high-energy energy hot-electrons, which maintains charge concentration in the interface field by injecting into (111)/(100)CeO₂, thereby provide thermodynamic contributions and inhibit bulk recombination. The tandem electric fields enable the (111)/(100)Au-CeO₂ to rapidly detect 5 ppm of NO₂ at room temperature with stability maintained within 20 s.