Enhanced NO2 gas sensing properties based on Rb-doped hierarchical flower-like In2O3 microspheres at low temperature

Highly sensitive NO2 gas sensor based on Rb-doped hierarchical flower-like In2O3 microspheres and the possible gas sensing mechanism. [Display omitted] •Rb-doped hierarchical flower-like In2O3 microspheres were successfully synthesized via a facile solvothermal method.•Sensor response to NO2 was significantly enhanced by slight alkali metal Rb doping.•The mechanism for enhanced NO2 gas sensing performances was discussed in detail. In this work, Rb-doped hierarchical flower-like In2O3 microspheres were synthesized via a facile one-step solvothermal method along with the subsequent thermal treatment. The morphology and structure of the as-synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Gas sensors based on the pure and Rb-doped In2O3 were fabricated and their gas sensing properties were systematically investigated. The sensors based on 1 mol% Rb-doped In2O3 exhibited ultrahigh response (Rg/Ra = 1502) to 5 ppm NO2 at 75 °C, which was over 2 times higher than that of pure In2O3. Moreover, the sensors showed good response towards NO2 down to ppb level (Rg/Ra = 10.2–100 ppb), a very low theoretical detection limit of 3.5 ppb, high selectivity and reliable repeatability. The excellent and enhanced NO2 gas sensing properties were mainly owing to its high specific surface area, novel hierarchical structure and increased surface chemisorbed oxygen species induced by Rb doping.