Assembly of stacked In2O3 nanosheets for detecting trace NO2 with ultrahigh selectivity and promoted recovery

Abstract

Assembly of two-dimensional (2D) nanosheets into organized three-dimensional (3D) architectures, coupled with open interspaces and surface-rich nanopores, is favorable for gas-interface diffusion and reaction. In this case, this kind of In2O3 morphology consisted of stacked nanosheets is successfully prepared through a facile hydrothermal and subsequent annealing route. And its morphology evolution route is also investigated using a time-dependent reaction. The gas sensor fabricated using this In2O3 product shows a remarkable response (Rgas/Rair = 5208.57) towards 20 ppm NO2, and an obvious response to 0.1 ppm NO2 at 100 °C. Moreover, the sensor signal can achieve a fast recovery after NO2-sensing event using a pulse-heating strategy. A negligible interference is also observed when exposed to other interfering vapors (including ethanol, acetone, toluene, NH3, and H2S), even though the concentrations of these gases are 100-folds than that of NO2. This ultrahigh selectivity towards NO2 is further confirmed by the first-principles theoretical results. The apparent NO2-sensing of this stacked In2O3 nanosheet could be tracked from following aspects: well-defined 3D architectures (ultrathin 2D nanosheets with abundant active sites, interspaces and nanopores for fast gas-transfer), strong adsorption energy of NO2 molecules on the exposed In2O3{111} facet, and favorable desorption kinetics at suitable temperature.