Vacancy-assisted exposed Sn atoms enhancing NO room temperature sensing of SnSe nanoflowers.

NO is a hazardous gas extremely harmful to the ecosystem and human health, so effective detection of NO is critical. SnSe is a promising candidate for gas sensors owing to its unique layered configuration that facilitates the diffusion of gas molecules. Here, ultrathin self-assembled nanoflowers F-SnSe rich in defects were synthesized by a simple solvothermal method. It exhibits excellent gas sensing performances for NO at room temperature (25 °C), with a high gas sensing response of 8.6 for 1 ppm NO and a lower detection limit as low as 200 ppb, capable of sensitively detecting ppb-level NO. DFT calculations revealed that the presence of Se vacancies assists the central Sn atoms to break through the shielding effect of the surface Se atoms and become exposed active sites. The higher reactivity leads to more charge transfer and higher adsorption energy, which strongly promoted the adsorption of NO. This work verifies the important role of vacancies for the exposed active sites and provides new guidance for defect engineering to modulate the gas sensing performances of SnSe.