Unraveling the promoted nitrogen dioxide detection performance of N-doped SnO2 microspheres at low temperature

Nitrogen doping has been proven an efficient strategy to modulate the electronic structure of metal oxides to tune their properties. Herein, we report the synthesis of N-doped SnO2 microspheres through calcining the pristine SnO2 in NH3 atmosphere. Texture characterizations show that N–SnO2 microspheres exhibit 3D-porous architectures with a diameter of ca. 300–500 nm. After NH3 treatment, the SnO2 exhibits the formation of the N-doping and oxygen vacancies on the surface of the material, rich free-electrons and the narrow energy band. It is found that the as-prepared N-doped SnO2 microspheres at 200 °C (N–SnO2-200), show superior selectivity and high response (S = 155 to 5 ppm NO2) compared with its counterparts. DFT calculations and experimental results illustrate that N impurities and oxygen vacancies as N-induced active sites favor the adsorption of NO2 molecules; rich free-electrons increase the amount of adsorbed NO2 molecules; and the narrow energy band promotes the effectively electron transfer during the sensing reaction. Therefore, in this work we unravel the improved NO2 gas-sensing performances of the N-doped SnO2 and provide new guidance for the development of highly efficient metal oxide sensing materials for NO2 detection. •The N-doped SnO2 nanospheres were synthesized via NH3 heat treatment of the pristine SnO2.•The correlation between the content of N doping and the gas-sensing property was further studied.•The N–SnO2 nanospheres obtained at 200 °C shows improved response and selectivity to NO2 at 80 °C.•The improved sensing mechanism of the N–SnO2 sensor to NO2 was further studied via DFT calculation.