Two-Dimensional Janus Nanostructures M₂AB (M = Si, Ge, Sn, A/B = N, P, As) for Piezoelectric Power Generation

Abstract

Two-dimensional (2D) Janus structures, as a newly derived form of 2D materials, have recently attracted great attention due to their structural symmetry breaking along with a piezoelectric effect and potential applications in nanoscale sensors, surface acoustic waves, and energy harvesters. To date, 2D Janus materials mainly appear in the IV−VI and III−V systems but are scarce involving the IV−V elements. Hereby, utilizing firstprinciples structure prediction, a stable IV−V−V family of 2D Janus structure 1T-M 2 AB (M = Si, Ge, Sn, A/B = N, P, As) was proposed. Their electronic, elastic, and piezoelectric properties are systematically investigated and compared. The calculated piezoelectric coefficient results reveal that the 1T-Sn 2 NP exhibits superior piezoelectric performance with a high in-plane piezoelectric constant (−8.07 pm/V), beyond many known 2D piezoelectric materials. Three independent factors of charge density distribution, vertical mirror asymmetry, and electrostatic potential gradients were assessed, which can well account for the piezoelectric characteristics of 1T-M 2 AB. This work not only demonstrates the potential applications of 2D Janus 1T-M 2 AB monolayer in piezoelectric devices but also enriches the family of 2D Janus structures.

Thermal Transport Properties of Two-Dimensional Janus MoXSiN2 (X = S, Se, and Te)

“…Two-dimensional materials (2D) benefiting from unique physical and chemical properties have garnered considerable attention and are potentially applied in various fields, including catalysis, , piezoelectricity, , and optoelectronics. − Among them, 2D materials with extremely high or low lattice thermal conductivity (κ l ) play a vital role in engineering thermal management and thermoelectric applications. − Notably, materials like graphene (∼5000 W/mK), , h-BN (751 W/mK), , PdSe 2 (3 W/mK), , and GeAs 2 (0.68 W/mK), , all of which have been successfully synthesized, demonstrated significant potential in engineering thermal management and thermoelectricity. However, challenges persistgraphene lacks a bandgap, PdSe 2 has a thermal-to-electric conversion efficiency of less than 5%, and challenges in exfoliating GaAs 2 due to the quasi-covalent bonds between layerswhich limit their practical applications.…”

Piezoelectric, Thermoelectric, and Photocatalytic Water Splitting Properties of Janus Arsenic Chalcohalide Monolayers

“…The piezoelectric properties of 2D monolayers are specified by in-plane ( d 11 ) and out-of-plane ( d 31 ) piezoelectric coefficients. Janus TiXY (XY = SCl and SeBr), group IV(A) Janus dichalcogenides, YBrI, MoAZ 3 H (A = Si and Ge: Z = N, P, and As), BiXY (X = S, Se, and Te; Y = F, Cl, Br, and I), PtXO (X = S and Se), MoSSiX 2 (X = N, P, and As), BMX 2 (M = Ga and In; X = S and Se), M 2 AB (M = Si, Ge, and Sn; A/B = N, P, and As), and γ-Ge 2 XX’ (X, X’ = S, Se, and Te) show a very high out-of-plane piezoelectric behavior, which is beneficial for piezoelectric devices. Furthermore, the corrected solar-to-hydrogen conversion efficiencies of Janus monolayer-based photocatalysts such as WSSe, MoSSe, PtSSe, WSeTe, AsTeX (X= Cl and Br), AsXY (X= Se and Te; Y = Br and I), and AlXY (X= S and Se; Y= Cl, Br, and I) exceed the 10% criteria for commercial use of photocatalysts.…”