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

Highlights: • The stacked In₂O₃ nanosheets with interspaces and rough surfaces were successfully prepared. • The adsorption energies were calculated by first-principles theoretical method to confirm the ultrahigh NO₂ selectivity. • This In₂O₃-based sensor presented a fast recovery rate under pulse-heating strategy. 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 (R_gas/R_air = 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{1 1 1} facet, and favorable desorption kinetics at suitable temperature.