Enhanced H2S Gas-Sensing Performance of Zn2SnO4 Lamellar Micro-Spheres

With the rapid development of industry, the discharge of sulfide gas has been increasing in recent decades, which results in severe air pollution. H2S, as the typical representation of sulfide, is a harmful and toxic acidic gas and widely used in various industries. Even at low concentrations, it can cause hypoxia and seriously threatens the safety of human. When the concentration reaches 1 mg/L (659 ppm) or higher, inflammation or death will occur. According to the U. S. Scientific Advisory Board on Toxic Air Pollutants, the acceptable concentration of H2S in the environment is less than 83 ppb (North Carolina Department of Environment and Natural Resources, 20031). Therefore, it is necessary to fabricate gas sensors which can detect ppb-level H2S in time to reduce the environmental pollution and harm to human. Zinc stannate (Zn2SnO4) is a typical n-type ternary semiconductor, and has been employed as important multifunctional material in the fields of photocatalytic activity (Das et al., 2017), solar cells (Li et al., 2015), lithium ion batteries (Lim et al., 2016), and so forth. Especially, owing to the excellent gas-sensing performance of ZnO and SnO2 (Sukunta et al., 2017; Zhu and Zeng, 2017; Zhu et al., 2018), the application of Zn2SnO4 in the field of gas sensors has attracted extensive attention (An et al., 2015; Zhao et al., 2016; Yang et al., 2017). Up to now, only one case has concerned on the detection of H2S with Zn2SnO4 hollow octahedron (Ma et al., 2012), which showed the response to H2S with the detection limit being 1 ppm at 260 C. Meanwhile, such reported Zn2SnO4 sensor presents poor selectivity. Apparently, the sensor cannot satisfy the need of practical application for the detection of ppb-level H2S, especially in a complex environment involving other interfering gases due to its poor selectivity and higher working temperature. In view of the fact that gas-sensing performance of materials is highly dependent on their micro-structure and surface state (Yu et al., 2017; Zhang et al., 2018), therefore, it would be a meaningful work to prepare Zn2SnO4 with novel morphology to further decrease the working temperature and improve the selectivity and stability, thus performing the detection of ppb-level H2S. In this work, Zn2SnO4 lamellar micro-spheres have been synthesized by a facile ethylenediamine-assisted hydrothermal method followed by calcining at 600C. The diameter of micro-spheres is ∼1μm and they are composed of nanosheets with thickness of ∼85 nm. The sensor fabricated from the micro-spheres shows good response and selectivity to H2S at 170 C, and the lowest detection limit is down to 50 ppb. Moreover, it shows good linear relationship in the range of ppb (50–1000 ppb) and ppm (3–50 ppm) level. Meanwhile, the gas-sensing mechanism is also investigated.