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

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 (similar to 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 degrees 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.