Specific Sn–O–Fe Active Sites from Atomically Sn-Doping Porous Fe2O3 for Ultrasensitive NO2 Detection

Abstract Conventional gas sensing materials (e.g., metal oxides) suffer from deficient sensitivity and serve cross-sensitivity issues due to the lack of efficient adsorption sites. Herein, the heteroatom atomically doping strategy is demonstrated to significantly enhance the sensing performance of metal oxides-based gas sensing materials. Specifically, the Sn atoms were incorporated into porous Fe 2 O 3 in the form of atomically dispersed sites. As revealed by X-ray absorption spectroscopy and atomic-resolution scanning transmission electron microscopy, these Sn atoms successfully occupy the Fe sites in the Fe 2 O 3 lattice, forming the unique Sn–O–Fe sites. Compared to Fe–O–Fe sites (from bare Fe 2 O 3 ) and Sn–O–Sn sites (from SnO 2 /Fe 2 O 3 with high Sn loading), the Sn–O–Fe sites on porous Fe 2 O 3 exhibit a superior sensitivity ( R g / R a = 2646.6) to 1 ppm NO 2 , along with dramatically increased selectivity and ultra-low limits of detection (10 ppb). Further theoretical calculations suggest that the strong adsorption of NO 2 on Sn–O–Fe sites (N atom on Sn site, O atom on Fe site) contributes a more efficient gas response, compared to NO 2 on Fe–O–Fe sites and other gases on Sn–O–Fe sites. Moreover, the incorporated Sn atoms reduce the bandgap of Fe 2 O 3 , not only facilitating the electron release but also increasing the NO 2 adsorption at a low working temperature (150 °C). This work introduces an effective strategy to construct effective adsorption sites that show a unique response to specific gas molecules, potentially promoting the rational design of atomically modified gas sensing materials with high sensitivity and high selectivity.