Adsorption of toxic gases on silicene/Ag(111)

Silicene is a two-dimensional nanomaterial, composed of Si atoms arranged into a buckled honeycomb network. It has become of great interest in recent years due to its remarkable properties such as its natural compatibility with current silicon-based technology. Due to its extreme thinness on the nanoscale, and large lateral dimensions, it has potential applications in gas sensing, gas storage and components in modern electronic devices. In this work, density functional theory calculations and ab initio molecular dynamics simulations are used to examine the reaction of SO₂, NO₂ and H₂S on the Si/Ag(111) surface. It was shown that each gas will adsorb on the surface in different orientations and adsorption sites. SO₂ and NO₂ were found to chemisorb on the surface, whereas H₂S was found to physisorb. SO₂ and H₂S adsorb associatively, whereas NO₂ readily dissociates, producing adsorbed oxygen, and gaseous NO. At elevated temperatures, the SO₂ and NO₂ remain strongly bound to the surface, resulting in poisoning of the silicene, while H₂S readily desorbs. Ab initio molecular dynamics also show that NO₂ will selectively bind before SO₂ when both gases are present in the same environment. This work shows that Si/Ag(111) may provide useful properties for gas sensing and storage applications.