In the present study, crystal-facet-dependent gas sensing performance was thoroughly investigated and sensing mechanism of TiO2 was elaborated in depth. Anatase TiO2 nano-polyhedron with highly reactive (001) facet was successfully synthesized via a one-pot hydrothermal method using fluoride as facet stabilizer and was utilized for fabrication of carbon monoxide gas sensors, followed by characterization of microstructure, phase-purity and gas-sensing properties. Chemiresistive properties of (001)dominated gas sensor exhibit superior response to CO with a maximum response of 27.9 at 300 ppm in optimum working temperature as 350 degrees C. Particularly, first-principle calculation was carried out to expound the sensing mechanism, which shows that CO adsorption on (001) facet is more stable and favorable than that on normally exposed (101) facet, corroborating the reactive nature of (001) facet. (C) 2018 Elsevier B.V. All rights reserved.