FeSe₂/Hematite n-n heterojunction with oxygen spillover for highly efficient NO2 gas sensing

Increasing the efficiency of nitrogen dioxide (NO2) sensing has been researched in-depth owing to the destructive and pernicious impacts of the gas on both the environment and human health. In this work, a novel n-n FeSe2/ hematite heterojunctions have been constructed through the controllable surface oxidation of FeSe2 nanoparticles and used for NO2 detection. Theoretical calculations suggest that the FeSe2/Fe2O3 interface can facilitate the electron and mass transfer through the n-n junction and oxygen spillover effect, energetically contributing to enhanced NO2 adsorption. In terms of NO2 sensing, the FeSe2/Fe2O3 nanocomposite exhibits a higher response (14.1-100 ppm) and faster sensing kinetics (10-30 s) than its FeSe2 and Fe2O3 counterparts. Such a heterostructure also demonstrates a ppb-level detection capacity, outstanding stability and selectivity to NO2 gas against other interfering gases at low temperatures (110 celcius). In situ Raman and Mott-Schottky measurements were further conducted to analyze the interface electronic properties and NO2 gas adsorption behaviors. The results from this investigation suggest that the NO2 gas could be reversibly chemi-adsorbed and desorbed on the surface of the FeSe2/Fe2O3 heterostructure for fast sensing response and recovery. This study presents fundamental insights into the rational design and implementation of highly efficient NO2 sensing materials through oxide/chalcogenide interface coupling.