H2S sensor based on SnO2 nanostructured film prepared by high current heating

In this work, SnO2 nanostructures prepared by a new high current heating (HCH) route are systematically studied for H2S gas sensing applications. In addition, their gas-sensing properties are compared with those of high-performance SnO2 nanoparticles prepared by flame spray pyrolysis (FSP). The SnO2 nanostructures were fabricated by gradually heating 30%SnO/70%C wires to a high temperature by passing high current in argon atmosphere. The material properties were characterized by XRD, AFM, SEM, EDS, TEM and XPS. The nanostructures formed around the wire were found to be mainly one-dimensional SnO2 nanowires (NWs) (10-100 nm in diameter and tens to hundreds micrometers in length) with high aspect ratios (∼1000) and occasionally hierarchical nanoflowers while zero-dimensional SnO2 nanoparticles (5-20 nm) were produced by FSP process. The sensing films were fabricated by spin coating of SnO2 powders made by both methods above Al2O3 substrates equipped with Au interdigitated electrodes and tested toward H2S (0.2-10 ppm) at 150-350 °C. It was found that the SnO2 NWs fabricated by HCH showed high and rapid response to H2S with a high response of ∼380 and a short response time of ∼2.3 s at 10 ppm of H2S and a low optimal temperature of 250 °C. A comparison between the two SnO2 materials reveals that HCH-made SnO2 NWs exhibits better H2S-sensing performances in terms of sensor response, response time and optimal operating temperature than FSP-made SnO2 nanoparticles. The superior sensing performance of SnO2 NWs could be attributed to better physical properties, particularly higher surface-to-volume ratio and highly reactive surface of single crystal NWs. Therefore, the SnO2 NWs sensor prepared by HCH is a promising candidate for sensitive detection of H2S.