Selenium-doped hematite (α-Fe2O3) hollow nanorods for highly sensitive and selective detection of trace NO2

Abstract

The selective and rapid detection of harmful gases, particularly nitrogen dioxide (NO₂), is critical for improving air quality and safeguarding human health, necessitating the development of advanced sensing materials with high sensitivity and selectivity. Density functional theory (DFT) calculations indicate that selenium (Se) doping optimizes the electronic structure of Fe₂O₃, improving its adsorption capacity for NO₂ molecules. With the aid of DFT calculations, hollow Fe₂O₃ nanorods and Se-doped Fe₂O₃ (Se–Fe₂O₃) nanorods have been synthesized and systematically evaluated for their structural and gas-sensing properties. The optimized Se–Fe₂O₃ demonstrates significantly higher responses to 10 and 20 ppm NO₂ than those of the pristine Fe₂O₃ (∼2.4 and 2.9 times higher), along with fast kinetics, a low detection limit (27 ppb), excellent sensing stability and NO₂ selectivity at 130 °C. Both theoretical and experimental investigations indicate that the doped Se atoms act as electron donors, enhancing the surface Lewis basicity of Fe₂O₃. This increased surface Lewis basicity facilitates the adsorption of acidic NO₂, thereby boosting its detection sensitivity. This research establishes surface acidity and basicity as critical factors in the rational design of efficient NO₂ sensors through doping modifications.