Oxygen vacancy engineering of self-doped SnO2-x nanocrystals for ultrasensitive NO2 detection

It remains a great challenge to engineer oxygen vacancies in metal oxides and elucidate the interrelation between oxygen vacancy contents and gas sensing performance. Herein, we report the self-doping of SnO2-x nanocrystals (NCs) through a solvothermal reaction using Sn powder and SnCl4 as precursors. The effect of Sn2+ doping concentration in the SnO2-x lattice on the nanocrystal size, band structure, and oxygen vancancies was investigated in detail. Gas-sensing tests revealed that the SnO2-x NCs showed ultra-high sensitivity to NO2 with low optimal operating temperature (100 degrees C). The detection limit of the sensor was as low as 500 ppb. This phenomenon is attributed to the active role of oxygen vancancies during the surface reactions with NO2, which was substantiated by in situ reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). This work highlights the possibility of simultaneous engineering of surface energistics and electronic properties of SnO2 based materials and provides an effective strategy to achieve excellent gas sensing performance for NO2 gas sensors.