Three-dimensional TiO2/SiO2 composite aerogel films via atomic layer deposition with enhanced H2S gas sensing performance

The SiO2 aerogel films with three dimensional (3D) networks were chosen as the templates to deposit TiO2 nanoparticles by atomic layer deposition (ALD). The microstructure, morphology and gas sensing properties of the composite aerogel films were investigated. The composite aerogel films kept the mesoporous structures with TiO2 nanoparticles uniformly coated on. After the 500 degrees C calcination, the TiO2 nanoparticles changed from amorphous to anatase phase. The calcined composite aerogel films were used to fabricate the gas sensor to detect H2S gas. The sensor had an excellent gas sensitivity of 1.34 with the response and recovery time of 53 and 74 s, respectively, at 250 degrees C when the H2S gas concentration was as extremely low as 0.5 ppm. The sensor still had a high gas sensitivity with the H2S concentration of 10 ppm even when the operating temperature was 100 degrees C. Compared to other H2S gas sensors based on TiO2 materials, the enhanced sensing performance could be due to the larger specific surface area of the aerogel template, the smaller grain size and the lattice mismatch between TiO2 nanoparticles and SiO2 aerogels, which made the composite aerogel films had more active sites and lattice defects, resulting in the increase of oxygen vacancy and enhancement of the gas sensitivity.