Preadsorption of O2 on the Exposed (001) Facets of ZnO Nanostructures for Enhanced Sensing of Gaseous Acetone

The O2 preadsorption properties prior to the application for nanomaterials have rarely attracted attention; however, they greatly affect the surface nature between gas and nanomaterials. Here, a hierarchically ZnO nest-like architecture (ZnO NAs) with nanosheets was synthesized by a facile hydrothermal method without structure-directing agents and templates. The percentage of exposed (001) facet for ZnO NAs is ∼95% according to its micromorphology. A gas sensor fabricated by ZnO NAs exhibits high sensitivity, low detection limit, fast response, and good selectivity to acetone at the low working temperature (105 °C). The distinct gas-sensing properties of ZnO NAs are mainly attributed to the specific surface area (63.46 m2/g) and high active (001) facet for the nanosheets. Note that a preadsorption of O2 from air on ZnO NAs and the gas reaction mechanism are put forward based on the preadsorbed behavior and target gas response. Moreover, by the aid of first-principles on the analysis of its surface adsorption energy and adsorption structure at (001) facet of ZnO NAs, it is identified that an oxygen preadsorption step on the facet occurs once it makes contact with air due to a lowest surface adsorption energy (−3.149 eV) for oxygen molecule. After the O2 preadsorption onto the surface, acetone is with the lowest surface adsorption energy of −0.687 eV, assigned to a chemical adsorption compared with the other gases. It benefits the acetone adsorption on the (001) facet for ZnO NAs, as well as following electron transfer and gas response. The sensitivity and selectivity for gas sensor based on ZnO NAs are well certified by both gas-resistance response and computational simulation.