Self-template synthesis of spherical mesoporous tin dioxide from tin-polyphenol-formaldehyde polymers for conductometric ethanol gas sensing

Abstract

Spherical mesoporous tin dioxides are emerging sensing materials for fabrication of gas sensor applied in various fields. However, the synthesis of spherical mesoporous SnO2 with uniform shape and small diameter (i.e., <100 nm) is still challenging. Herein, spherical mesoporous SnO2 materials with tunable diameter (55−110 nm), large pore size (∼5.8 nm) and high specific surface area (80.9-185.6 m2/g) are synthesized via a self-template strategy by direct thermal decomposition of tin-polyphenol-formaldehyde polymers (TPFPs). Spherical TPFPs are synthesized via a sol-gel process using a low-cost, nontoxic and renewable natural polyphenol (i.e., tannic acid) as a ligand, formaldehyde as a cross-linking agent, tin ions as a metal source in alkaline conditions. Block copolymers can regulate the polymerization process and promote the formation of uniform spheres. The diameter of TPFPs and their derived spherical mesoporous SnO2 can be adjusted by changing the amount of block copolymers. The gas sensors fabricated from spherical mesoporous SnO2 exhibit excellent sensitivity to ethanol ([email protected] ppm), fast response and recovery time (4 s / 44 s), good repeatability and long-term stability. This work demonstrates a reliable method for synthesis of spherical mesoporous SnO2, which could be potentially applied in catalysis, sensing and energy storage.