First-Principles Calculations of Holey Graphyne for Sensing Nitrogen-Containing Gases and Humidity

This study employs density functional theory (DFT) to examine the properties of holey graphyne (HGY) upon adsorption of nitrogen-containing gases (NO₂, NO, NH₃) and water (H₂O) for evaluating its potential for gas sensing. NO exhibits the highest adsorption energy on pristine HGY, creating a strong interaction with the electronic band structure, while other gases display weaker adsorption energies, affecting the substrate’s electronic structure to a lesser extent. All four molecules are predicted to have a positive free energy change upon adsorption, resulting in poor surface coverage at temperatures relevant for gas sensing. To improve HGY’s effectiveness as a sensor material, boron (B) and nitrogen (N) substitutional doping are introduced, producing p- and n-type free charge carriers, respectively. B-doping leads to strong chemisorption for the nitrogen-containing molecules, resulting in high surface coverage but also causing very long recovery times. Similar behavior is observed with H₂O, though with weaker chemisorption. N-doping significantly increases the NO adsorption energy relative to the other three molecules, leading to high surface coverage and reasonable recovery times. Band structure analysis indicates that N-doped HGY results in the passivation of the n-type doping. Conversely, for NO₂, NH₃, and H₂O, only minor changes occur in the HGY electronic structure near the band edges, with little or no dopant passivation, suggesting minimal impact on electrical conductivity upon molecular adsorption. These findings imply that N-doped HGY shows promise for NO detection, offering high sensitivity, selectivity, and robust conductance changes. The study highlights the potential of defect engineering to tailor HGY’s properties for detecting specific molecules.