Stabilizing the isolated Sn2Bi nanosheet and tailoring its electronic structure by chemical functionalization: A computational study

Very recently, a two-dimensional nanomaterial, the Sn2Bi nanosheet, has been synthesized on a silicon wafer. Here, utilizing first-principles calculations, we explore the structural stability and electronic property of the free-standing Sn2Bi nanosheet. Different from the experimentally supported one, we find that the isolated Sn2Bi nanosheet is a metal and suffers from dynamical instability. Its structural stability can be greatly enhanced by surface hydrogenation, which can completely eliminate the soft modes from the high-buckled tricoordinate Sn atoms. Both the single-side and double-side hydrogenated Sn2Bi (s-/d-H-Sn2Bi) nanosheets possess robust energetic, dynamical, and thermal stabilities and exhibit a semiconducting behavior akin to the supported Sn2Bi system. In particular, the band edge of the s-H-Sn2Bi nanosheet can saddle the redox potential of water under a strong alkaline condition, and its analogue by the iodization (s-I-Sn2Bi) is even suitable for photocatalytic water splitting under the pH neutral condition. Moreover, these functionalized systems exhibit high solar-to-hydrogen efficiencies, which reach up to 18% and 36% in the s-H-Sn2Bi and s-I-Sn2Bi nanosheets, respectively. Our study demonstrates that the functionalized Sn2Bi nanosheets have robust structural stabilities and promising electronic properties for potential applications in nano-energy and nano-electrics. Published under license by AIP Publishing.