First theoretical framework of Al9N9 and B9N9 nanorings for unveiling their unique detection and sensing potential for SF6 decomposition gases (H2S, SO2, SOF2, and SO2F2): toward real-time gas sensing in high-voltage power systems

Abstract

Sulfur hexafluoride (SF₆) is widely used as an insulating gas in high-voltage electrical equipment due to its excellent dielectric properties. However, its decomposition under electrical discharges can generate toxic and corrosive byproducts such as H₂S, SO₂, SOF₂, and SO₂F₂, which pose serious threats to insulation integrity and the reliability of power systems. Rapid and accurate sensing and detection of these decomposition products is thus critical for fault diagnosis and preventative maintenance. Despite various experimental advances, the development of efficient, sensitive, and real-time nanomaterial-based gas sensors remains a challenge. In this study, we systematically investigate the sensing capabilities of Al₉N₉ (AlN) and B₉N₉ (BN) nanorings for SF₆ decomposition gases using density functional theory (DFT) with the B3LYP-D3/6-31G(d,p) method. Different key electronic and structural evaluations including adsorption energy (E_ads) measurements, energy gap (E_g) determinations, natural bond orbital (NBO), density of states (DOS), thermodynamic studies, atom in molecules (AIM), non-covalent interactions (NCI) and sensing mechanism were carried out to assess the sensing performance. The adsorption of these gases on AlN nanoring results in higher adsorption energies ranging from −8.690 kcal mol⁻¹ to −38.221 kcal mol⁻¹ while these gases are weakly adsorbed on BN nanorings (−7.041 to −7.855 kcal mol⁻¹). The reduction of the energy gap is observed after the adsorption of SF₆ decomposed gases on both rings. The most notable reduction is observed after the adsorption of SO₂ on AlN (1.103 eV) and BN (2.883 eV) nanorings. The study demonstrated that SO₂ showed maximum sensitivity on BN nanorings (0.9797), accompanied by a substantial work function increase of 36.715% which confirmed BN as the most reactive material for SO₂ detection. The adsorption of SF₆ on AlN and BN nanorings produced fast recovery times, which shows their potential for real-time sensor applications, with the increase in temperature further decreasing the recovery time. Both AlN and BN nanorings showed better detection performance for SO₂, while AlN nanorings proved more efficient for SOF₂ and SO₂F₂ detection because of their superior electrical conductivity, better charge transfer, and quicker recovery times. These findings recommend the integration of Al₉N₉ and B₉N₉ nanorings in advanced gas sensor technologies for real-time, reliable detection of SF₆ decomposition gases, crucial for enhancing the safety and efficiency of high-voltage power systems.