Tunable and optimal interlayer spacing of 2D VS2 with high response and fast recovery for NO2 detection

Abstract

Due to the restricted interlayer spacing, the large active regions between the interlayers of most two-dimensional (2D) materials are difficult to be utilized efficiently, which greatly limits their performance for gas sensing. Herein, a novel NO2 sensor based on expanded VS2 (abbreviated as VS2-E) is reported by regulating the interlayer spacing to 11.6 Å (VS2-E3). Compared with VS2-N (natural interlayer spacing of 5.8 Å), VS2-E1 (10.0 Å) and VS2-E2 (10.2 Å), the increased interlayer spacing of the VS2-E3 significantly improved its NO2 sensing performance. With a high response (∼2.77–10 ppm NO2), rapid response/recovery speed (∼10/10 s), low detection limits (distinct response to 200 ppb NO2), and good stability at 100 °C, the sensor based on VS2-E3 demonstrates excellent NO2 sensing qualities. In addition, the interlayer sensing mechanism is explained by simulating the diffusion movement of NO2 between different spacing VS2 interlayers. Enlarging the interlayer space boosts the interaction of VS2 and NO2, increases the diffusion coefficient of NO2 and accelerates their desorption between interlayers, thereby evidently enhancing the response intensity and the recovery speed. These results suggest that VS2-E3 has promising prospect in the realm of low-concentration and rapid NO2 detection.