Combined Density Functional Theory Calculation and Non-Equilibrium Green's Function Approach to Predict the Sensitivity of Nitrogen-Containing Gases over PtTenS2-n Monolayers (n = 0–2)

Two-dimensional (2D) transition-metal dichalcogenide (TMD) monolayers are potential toxic gas sensors for next-generation industrial applications. In this study, we adopted density functional theory (DFT) calculations to investigate the sensing properties of harmful nitrogen-containing gases (NCGs) on Pt-based TMDs (PtTenS2-n monolayers, where n = 0-2). Our results showed that the electronic interactions of ammonia (NH3) on all TMDs and nitrogen oxides (NOx) on PtS2 were weak. However, the electronic interactions were strong between the NOx molecules and PtTe2 or Janus PtTeS monolayers. Moreover, the bandgap was reduced after NOx adsorption on the PtTe2 and Janus PtTeS monolayers; however, the reduced amplitude of NOx on the Janus PtTeS monolayer was more significant than that on the PtTe2 monolayer. By combining Non-Equilibrium Green's Function (NEGF) calculations, the sensitivities were all found to be poor for the NCGs on PtS2. Nitrogen dioxide (NO2) exhibited higher sensitivity than those exhibited by NH3 and nitric oxide (NO) at 1.0 V on the PtTe2 monolayer; therefore, the selectivity of NO2 was high under this condition. In addition, NO and NO2 possessed high sensitivities at 0.6 and 0.4 V on the Janus PtTeS monolayer, respectively. Consequently, the sensitivity of NOx molecules on the Janus PtTeS monolayer was higher than that on the PtTe2 and PtS2 monolayers at relatively low applied biases. The results of this study indicate that the Janus PtTeS monolayer is a promising NOx gas sensor with both high selectivity and sensitivity for NCG-sensing applications.