A fast response/recovery ppb-level H2S gas sensor based on porous CuO/ZnO heterostructural tubule via confined effect of absorbent cotton

The development of ZnO-based sensors towards the detection of trace H2S has recently aroused extensive attentions due to its very harmful to human health even at a concentration as low as 83 ppb. However, the fast response/recovery ZnO-based sensors for detecting ppb-level H2S were also challenging. In this study, porous CuO/ZnO heterostructural tubule was facilely and massively prepared by metal salt impregnation and subsequently calcination via confined effect of absorbent cotton. The influence of Cu2+ doping amounts and calcination temperature on the corresponding microstructure and gas sensing properties of the composites is investigated. The precursor with 3.67 at% Cu2+ doping was calcined at 600 °C to form heterostructural tubules (3.67 at% CuO/ZnO-600) with the specific surface area of 35.2 m2 g−1, which consist of monoclinic CuO (˜21.8 nm) and hexagonal ZnO (˜33.7 nm). The sensor based on 3.67 at% CuO/ZnO-600 shows better gas sensitivity to 50 ppb H2S at 170 °C with response and recovery times of 35 and 29 s, which represents the fastest response/recovery properties in reported ZnO-based ppb-level H2S sensors to date. Furthermore, the sensor has a low detection limit of 10 ppb and shows a wide linear range from 10 to 1000 ppb, good repeatability and long-term stability. Such excellent ppb-level H2S gas sensing performance is mainly ascribed to the inherent characteristics of hierarchically porous tubular structure, p-n heterojunction and surface adsorbed oxygen species. Moreover, the gas-sensing mechanism is also investigated in detail.