High-Response Room-Temperature NO2 Sensor and Ultrafast Humidity Sensor Based on SnO2 with Rich Oxygen Vacancy.

SnO2 nanosheets with abundant vacancies (designated as SnO2- x) have been successfully prepared by annealing SnSe nanosheets in Argon. The transmission electron microscopy results of the prepared SnO2 nanosheets indicated that high-density SnO2- x nanoplates with the size of 5-10 nm were distributed on the surface of amorphous carbon. After annealing, the acquired SnO2- x/amorphous carbon retained the square morphology. The stoichiometric ratio of Sn/O = 1:1.55 confirmed that oxygen vacancies were abundant in SnO2 nanosheets. The prepared SnO2- x exhibited excellent performance of sensing NO2 at room temperature. The response of the SnO2- x-based sensor to 5 ppm NO2 was determined to be 16 with the response time and recovery time of 331 and 1057 s, respectively, which is superior to those of most reported room-temperature NO2 sensors based on SnO2 and other materials. When the humidity varied from 30 to 40%, Δ R/ R was 0.025. The ultrafast humidity response (52 ms) and recovery (140 ms) are competitive compared with other state-of-art humidity sensors. According to the mechanistic study, the excellent sensing performance of SnO2- x is attributed to its special structure.