High-Response\nRoom-Temperature NO₂ Sensor\nand Ultrafast Humidity Sensor Based on SnO₂ with Rich Oxygen\nVacancy

Abstract

SnO₂ nanosheets\nwith abundant vacancies (designated\nas SnO_2–<i>x</i>) have been successfully\nprepared by annealing SnSe nanosheets in Argon. The transmission electron\nmicroscopy results of the prepared SnO₂ nanosheets indicated\nthat high-density SnO_2–<i>x</i> nanoplates\nwith the size of 5–10 nm were distributed on the surface of\namorphous carbon. After annealing, the acquired SnO_2–<i>x</i>/amorphous carbon retained the square morphology.\nThe stoichiometric ratio of Sn/O = 1:1.55 confirmed that oxygen vacancies\nwere abundant in SnO₂ nanosheets. The prepared SnO_2–<i>x</i> exhibited excellent performance\nof sensing NO₂ at room temperature. The response of the\nSnO_2–<i>x</i>-based sensor to 5 ppm NO₂ was determined to be 16 with the response time and recovery\ntime of 331 and 1057 s, respectively, which is superior to those of\nmost reported room-temperature NO₂ sensors based on SnO₂ and other materials. When the humidity varied from 30 to\n40%, Δ<i>R</i>/<i>R</i> was 0.025. The ultrafast\nhumidity response (52 ms) and recovery (140 ms) are competitive compared\nwith other state-of-art humidity sensors. According to the mechanistic\nstudy, the excellent sensing performance of SnO_2–<i>x</i> is attributed to its special structure.