Adsorption mechanism of different toxic gases onto pristine BNC2 and Al-doped BNC2 monolayers

Abstract

Graphene-based ternary BNC materials have been widely explored for the fabrication of gas sensors because of their various two-dimensional conjugated structures, high conductivity and large specific surface areas. To understand the essential physics and gas sensing properties, we focus on a sheet with equal concentration of C and BN, i.e. a BNC₂ sheet. Using density functional theory, we have explored the effects of doping of an aluminium (Al) atom on the structural and electronic properties of a ternary BNC monolayer. We have studied the adsorption mechanism of various gas molecules such as CO, CO₂, NO, NO₂, SO₂, and SO₃ on BNC₂ and Al@BNC₂ MLs. Doping of the Al atom in BNC₂ changes the structural as well as electronic properties of the host dramatically. The large-sized Al atom protrudes out from the BNC₂ ML. The induced defects due to doping of the Al atom in BNC₂ reduce the band gap of the BNC₂ ML and enhance the reactivity of the BNC₂ ML. The adsorption of CO, CO₂, NO, NO₂, SO₂, and SO₃ gas molecules shows higher interaction towards the Al@BNC₂ ML as compared to the BNC₂ ML. Among all the gas molecules, the maximum interaction of NO₂ gas molecules is found with the Al@BNC₂ ML. Adsorbed gas molecules act as charge acceptors from both the MLs. The improved conductivity of the Al@BNC₂ ML as compared to BNC₂ with the adsorption of gas molecules offers the basis for the development of ternary BNC-based gas sensors.