High sensitivity and selectivity chlorine gas sensors based on 3D open porous SnO₂ synthesized by solid-state method

A simple solid-state reaction method was employed to synthesize the three-dimensional open porous SnO₂ (3D OP-SnO₂) by grinding the mixture of tin tetrachloride pentahydrate, sodium hydroxide and sodium chloride. Sodium chloride worked as a template to build the 3D open porous structure. The morphological feature was three-dimensional open porous with diameters about 300–500 nm and the edge of the 3D open porous were composed of numerous SnO₂ nanoparticles with grain size around 5.8 nm. The chlorine (Cl₂) gas sensing properties of 3D OP-SnO₂ and bulk SnO₂ (B–SnO₂) sensors were systematically investigated. Gas response of the 3D OP-SnO₂ sensor was 792.85 to 5 ppm Cl₂ at 160 °C, which was 61 times higher than that of B–SnO₂. Such outstanding gas sensing performance was mainly ascribed to the small grain size, which resulted in the change of conductivity mechanism and the decreased mobility of electrons. Thereby, the resistance of OP-SnO₂ increased dramatically. Moreover, the unique structure and abundant oxygen vacancies also contributed to the excellent gas sensing performance, because they can elevate the specific surface area and provide sufficient Cl₂ adsorption sites.