Trace carbon nitride-decorated SnO2 lamella boosting ultra-high response and fast recovery of NO2 gas at low temperature

The low-temperature NO2 gas sensors with ultra-high response are more helpful for their real-time and accurate monitoring in complex environment, however, the relevant reports are very less. Herein, we firstly prepared graphitic carbon nitride (g-C3N4) by pyrolysis of inexpensive melamine, which was used as template and directly soaked into SnCl4 ethanol/water solution. Afterwards, the immersed precursors were calcined to generate different SnO2-based materials. Among, the morphology of g-C3N4/SnO2-5 calcined at 500 °C is lamella structure composed of trace g-C3N4 and small-size SnO2 nanoparticles, which possesses narrow mesopores, large specific surface area, rich oxygen vacancy defects, as well as high concentration of surface O2-(ad) species. Under the synergy of multiple favorable factors, g-C3N4/SnO2-5 sensor exhibits ultra-high response (S = 12171) for 10 ppm NO2 gas at 92 °C, which is 1.93 times than that of SnO2-6 sensor. It is also the highest response value among reported g-C3N4/metal oxide composites. In addition, this sensor has fast recovery time (5 s), low detection limit, good moisture resistance and stability. Thus, the simple g-C3N4 template method provides a new strategy for the fabrication of gas sensors with highly efficient sensing ability.