A fast response and recovery H2S gas sensor based on free-standing TiO2 nanotube array films prepared by one-step anodization method

The free-standing TiO2 nanotube (TiNT) array film was firstly synthesized by a one-step anodization method. The characterization results with SEM, TEM, XRD and EDX indicated that the main compound on the TiNT array film was titania with anatase phase, and the average inner diameter of the nanotube was around 110 nm with a wall thickness of 16 nm and a layer thickness of 3.8 mu m. Subsequently, the TiNT-based gas sensor was fabricated and its sensing properties toward H2S were investigated. The results showed that, operating under the optimum temperature of 300 degrees C, the TiNT-based gas sensor not only had excellent reversibility, selectivity and stability, but also attained the response values 4.5-26.2 to the detected H2S gas at 1-50 ppm, and good linearity between the sensor response and H2S concentration could be observed. Meanwhile, the response and recovery time of the sensor to 50 ppm H2S gas were as low as 22 s and 6 s, respectively. In addition, the growth mechanism of the free-standing TiNT array film and the gas sensing mechanism of the TiNT-based gas sensor towards H2S were also given in the article. Lastly, the outstanding gas sensing properties and easy fabrication of the TiNT-based gas sensor presented the potential industrial applications in the future.