Adsorption Behaviors of Small Molecules on Two-Dimensional Penta-NiN2 Layers: Implications for NO and NO2 Gas Sensors

Penta-NiN2 is a two-dimensional layered material with pentagonal atomic arrangement and has recently been manufactured in experiments (ACS Nano 2021, 15, 8, 13539). We study systematically the adsorption of CO, CO2, NO, NO2, NH3, and CH4 on penta-NiN2 nanosheet and its effects on electronic properties employing the first-principles method combined with the nonequilibrium Green's function. Excellent sensing performance of penta-NiN2 is predicted for the NOx (x = 1, 2) molecules based on energetic, geometric, and electric analyses. The adsorption of NO and NO2 gas molecules may convert penta-NiN2 from a nonmagnetic semiconductor to magnetic metal. A current enhancement around 800% can be observed in penta-NiN2 connected to a circuit after its adsorption of NO. The unique selectivity and sensitivity to adsorption suggest that penta-NiN2 may become a widely used gas sensor for NO and NO2.