Detection of SOF2 and SO2F2 through aluminium nitride nanosheets: A DFT study

Abstract

Detection of sulfuryl fluoride (SO2F2) and thionyl fluoride (SOF2) can be used to find out the degradation of sulfur hexafluoride (SF6), indicating gas insulation switchgear equipment failures. In the present work, we study through first-principle DFT calculations the SOF2 and SO2F2 adsorption on aluminium nitride nanosheets (AlNNS), with the aim of to evaluate the performance of this nanomaterial as gas sensor. First, we performed an energetic, geometric and bonding analysis, obtaining considerable adsorption energy values for SO2F2 and SOF2 (−1.63 and −1.93 eV, respectively), which suggests these gases are chemisorbed on the AlN surface. Furthermore, certain S−F bonds were broken during adsorption, while new Al−F and S−N overlaps were developed. Simultaneously, an important weakening was observed for Al−N bonds close to the adsorption site. The adsorption selectivity of AlNNS toward SO2F2 and SOF2 was also studied, noting that other molecules normally present in air show a lower reactivity.Band structure and electronic density of states were realized in order to evaluate the sensing capacity of AlNNS surface. The obtained plots show a notorious narrowing of the band gap after gas adsorption, particularly in the case of SOF2, so an important change in the conductivity of AlNNS could be expected during gas exposition. Charge density analysis reveals an important charge transfer from AlNNS to both adsorbed gases, which suggest that this nanomaterial could behave as an n-type semiconductor. These results seem to indicate that AlNNS could act with good sensibility and selectivity for SOF2 and SO2F2 detection, showing high potential as gas sensing material.