Activating the\nScreened Thermoelectric and Photocatalytic\nWater-Splitting Potential in Janus Sn<sub>2</sub>XY (X ≠ Y\n= Te, Se, and S) Monolayers via Doping and Strain Engineering

A recent\ntheoretical report discovered that the relatively\nnew\nJanus γ-Sn<sub>2</sub>XY (X ≠ Y = Te, Se, and S) monolayers\npossess enhanced piezoelectricity performance, with a reported near\nShockley–Queisser limit band gap (<i>E</i><sub>g</sub>) and high carrier mobility. Inspired by these positive traits, further\ndetailed studies on their untested green energy conversion properties\nare warranted. Herein, the unexplored thermoelectric and photocatalytic\nproperties of these materials have been extensively investigated using\nfirst-principles density functional theory, Boltzmann transport theory,\nand Bethe–Salpeter method, respectively. Their stability from\nenergy, mechanical, and thermal up to the 800 K viewpoint was, respectively,\nconfirmed via the cohesive energies, ab initio molecular dynamics,\nand elastic tensor coefficients analyses. Attributed to their intrinsically\nlow thermal conductivity, large Seebeck coefficients, and high electrical\nconductivity, the n-doped Sn<sub>2</sub>TeSe and Sn<sub>2</sub>TeS\nmonolayers exhibit a combined desirable figure of merit of ∼0.9\nand ultrahigh power factor above 0.06 W m<sup>–1</sup> K<sup>–2</sup> from 300 to 700 K, rendering them a promising candidate\nfor efficient thermoelectric energy conversion. Findings also reveal\nthat these monolayers have rather significant visible region optical\nabsorption spectra. Particularly, based on its HSE06-calculated band\nedges and free energy studies, Sn<sub>2</sub>TeS under minimal tensile\nstrain displays favorable photocatalytic water-splitting ability with\na solar-to-hydrogen conversion efficiency of 23.8%. Graphical analysis\nalso indicates the feasibility of CO<sub>2</sub> and lesser N<sub>2</sub> reduction by these monolayers.