Nonmetallic Atom Regulation for Enhanced NiPr Monolayer Sensing of SF₆ Decomposition Gases: A DFT Study

The identification and mitigation of SF₆ decomposition gases (SO₂, H₂S, HF, SOF₂, and SO₂F₂) are critical for environmental protection and human health. In this study, we utilized density functional theory (DFT) to systematically investigate the adsorption characteristics and sensing properties of these gases on pristine nickel-porphyrin (NiPr) and nonmetal-atom-modified nickel-porphyrin (NiNPr, N = B/O) monolayers. The studied results indicate that the NiPr monolayer is not suitable as a gas-sensitive material for the detection of SF₆ decomposition gas molecules due to its weak adsorption ability and low sensitivity. However, the incorporation of nonmetallic B and O atoms into the NiPr monolayer significantly enhances the binding energy, ensuring the structural stability of the resulting NiBPr and NiOPr monolayers. The bandgap values of these doped monolayers are reduced to 0.326 eV (NiBPr) and 0.057 eV (NiOPr) compared to 0.985 eV for the pristine NiPr monolayer. Notably, the NiBPr and NiOPr monolayers demonstrate enhanced adsorption energy for SO₂, H₂S, SOF₂, and HF gases (-0.56 eV to -1.08 eV), indicating chemical adsorption. A comprehensive analysis of the total electron density distribution, charge density difference, and density of states was conducted to elucidate the interaction mechanisms between the gases and the monolayers. Additionally, significant changes in work function and bandgap values confirm the high sensitivity of these monolayers. Recovery time assessments for gases including SO₂, H₂S, HF, SOF₂, and SO₂F₂ reveal that the NiBPr monolayer is viable as a reusable gas sensor for SO₂, H₂S, HF, and SOF₂, while the NiOPr monolayer is apt for sensing H₂S, HF, and SOF₂ gases. These findings are significant in highlighting the potential of NiBPr and NiOPr monolayers as innovative sensors for the SF₆ decomposition gases.