First-principles Study Of Toxic Gas Molecules Adsorption On The Two-dimensional GaN Nanosheet

In this paper,the adsorption characteristics of toxic gases?H₂S,NH₃,SO₂,CO and NO?interacting with two-dimensional GaN single-layer nanosheets simulated in the Vienna ab initio simulation package?VASP?are investigated by using the first-principles methods based on density functional theory?DFT?.The sensitivity and selectivity of gallium nitride monolayer?GaN-ML?adsorbing toxic gases are analyzed by comparing the adsorption energy of each system,the charges transfer of Bader calculation,the band structures and density of states of static non-self-consistent calculation,and the charge density difference obtained by VESTA.The electronic structure of the pristine GaN-ML is changed by introducing 3d,4d and 5d transition metal atoms and main group metal atom doping and single vacancy defects,which is to enhance the adsorption ability and sensitivity of GaN-ML for toxic gases.The gas adsorption characteristics of two-dimensional GaN nanomaterials are revealed by studying the geometry,stability,electronic properties and physical properties of toxic gases adsorbed on GaN nanosheets before and after modification.The studies demonstrate that the H₂S and NH₃ are physisorbed on pristine GaN-ML with small adsorption energy,charge transfer,and long adsorption distance.While chemical adsorption character of SO₂ on pristine GaN-ML can be obtained,which means that pristine GaN-ML is sensitive to SO₂.We find that the adsorption ability of pristine GaN-ML can be improved by introducing TM dopants.TM?Fe,Mn?doping can increase adsorption energy and charge transfer of the adsorbed systems,except for SO₂ adsorbed Fe doped GaN-ML.The enhancing interaction between adsorbed molecules and the TM doped GaN-ML can dramatically induce electrical conductivity changes.Therefore,the TM doped GaN-ML is more suitable for gas molecules detection compared with the pristine GaN-ML.In order to study the novel gas detection and sensing applications of GaN-ML for toxic gases?CO and NO?,the DFT-D2 method is used to describe the van der Waals forces existing between interactions in the paper.The calculations demonstrate that the pristine GaN-ML is not suitable for the detection of CO and NO due to its extreme insensitivity to them together with the existence of a physisorption nature.It is found that both N-vacancy defected GaN-ML and Fe-doped GaN-ML significantly increase the adsorption energy and charge transfer for CO adsorption.The CO adsorption causes the metallicity of N-vacancy GaN-ML to be converted to the half-metallic characteristics together with 100%spin polarization,and CO adsorption drastically changes the magnetic moment,indicating that N-vacancy GaN-ML exhibits excellent sensitivity to CO.However,Fe-doped GaN-ML is not conducive to CO detection.Moreover,N-vacancy defected and Pt-doped GaN-ML greatly enhance the adsorption ability towards NO compared to other substrates,and the presence of stronger orbital hybridization suggests that the interaction between them is chemisorption.Therefore,N-vacancy defected GaN-ML and Pt-doped GaN-ML can serve as potential materials in future NO sensing devices.The research results are expected to provide a better theoretical basis and possible ideas for the design and preparation of two-dimensional GaN-based gas sensing materials with high sensitivity and faster response.