Three-Dimensional Mesoporous Graphene Aerogel-Supported SnO₂ Nanocrystals for High-Performance NO₂ Gas Sensing at Low Temperature

A facile and cost-efficient hydrothermal and lyophilization two-step strategy has been developed to prepare three-dimensional (3D) SnO₂/rGO composites as NO₂ gas sensor. In the present study, two different metal salt precursors (Sn²⁺ and Sn⁴⁺) were used to prepare the 3D porous composites. It was found that the products prepared from different tin salts exhibited different sensing performance for NO₂ detection. The scanning electron microscopy and transmission electron microscopy characterizations clearly show the macroporous 3D hybrids, nanoporous structure of reduce graphene oxide (rGO), and the supported SnO₂ nanocrystals with an average size of 2–7 nm. The specific surface area and porosity properties of the 3D mesoporous composites were analyzed by Braunauer–Emmett–Teller method. The results showed that the SnO₂/rGO composite synthesized from Sn⁴⁺ precursor (SnO₂/rGO-4) has large surface area (441.9 m²/g), which is beneficial for its application as a gas sensing material. The gas sensing platform fabricated from the SnO₂/rGO-4 composite exhibited a good linearity for NO₂ detection, and the limit of detection was calculated to be as low as about 2 ppm at low temperature. The present work demonstrates that the 3D mesoporous SnO₂/rGO composites with extremely large surface area and stable nanostructure are excellent candidate materials for gas sensing