Normal-pressure microwave rapid synthesis of hierarchical SnO2@rGO nanostructures with superhigh surface areas as high-quality gas-sensing and electrochemical active materials

Abstract

Hierarchical SnO₂@rGO nanostructures with superhigh surface areas are synthesized via a simple redox reaction between Sn²⁺ ions and graphene oxide (GO) nanosheets under microwave irradiation. XRD, SEM, TEM, XPS, TG-DTA and N₂ adsorption–desorption are used to characterize the compositions and microstructures of the SnO₂@rGO samples obtained. The SnO₂@rGO nanostructures are used as gas-sensing and electroactive materials to evaluate their property–microstructure relationship. The results show that SnO₂ nanoparticles (NPs) with particle sizes of 3–5 nm are uniformly anchored on the surfaces of reduced graphene oxide (rGO) nanosheets through a heteronucleation and growth process. The as-obtained SnO₂@rGO sample with a hierarchically sesame cake-like microstructure and a superhigh specific surface area of 2110.9 m² g⁻¹ consists of 92 mass% SnO₂ NPs and ∼8 mass% rGO nanosheets. The sensitivity of the SnO₂@rGO sensor upon exposure to 10 ppm H₂S is up to 78 at the optimal operating temperature of 100 °C, and its response time is as short as 7 s. Compared with SnO₂ nanocrystals (5–10 nm), the hierarchical SnO₂@rGO nanostructures have enhanced gas-sensing behaviors (i.e., high sensitivity, rapid response and good selectivity). The SnO₂@rGO nanostructures also show excellent electroactivity in detecting sunset yellow (SY) in 0.1 M phosphate buffer solution (pH = 2.0). The enhancement in gas-sensing and electroactive performance is mainly attributed to the unique hierarchical microstructure, high surface areas and the synergistic effect of SnO₂ NPs and rGO nanosheets.