Competitive influence of surface area and mesopore size on gas-sensing properties of SnO₂ hollow fibers

In this work, the effects of surface area and mesopore size on gas-sensing properties of SnO₂ hollow microfibers assembled by nanocrystals were investigated. When the sintering time was increased from 2 to 24 h, the specific surface area (SSA) of SnO₂ microfibers decreased from 103.6 to 59.8 m² g⁻¹, whereas the mesopore diameter gradually increased from 2.8 to 10.9 nm. Interestingly, it was found that their gas-sensing properties to ppb-level formaldehyde were determined by both SSA and mesopore size. The gas response increased firstly and then decreased with decreasing SSA and increasing mesopore size and reached the maximum value when the sintering time was 11 h. When the sintering time was <11 h, mesopore size (<8.5 nm) dominated sensing behavior by controlling gas diffusion rate. Once the sintering time was more than 11 h, the decreased SSA (<70.8 m² g⁻¹) dominated sensing performance by influencing the surface reaction activity. Therefore, the competitive influence of surface area and mesopore size on gas-sensing properties of mesoporous SnO₂ microfibers was revealed. This work could provide a new understanding for microstructural design of the mesoporous gas-sensing metal oxide materials.