Computational discovery of diverse functionalities in two-dimensional square disulfide monolayers: auxetic behavior, high curie temperature ferromagnets, electrocatalysts, and photocatalysts

Abstract

By means of systematic density functional theory (DFT) computations, we identified 12 stable two-dimensional (2D) disulfide monolayers featuring a square lattice from a pool of 68 candidate monolayers. Our screening process comprehensively assessed their thermodynamic, dynamic, mechanical, and thermal stabilities. These 12 stable monolayers (S-XS₂ with X = Si, Ge, Sn, Pb, Ti, V, Cr, Mn, Zr, Mo, Re, and Os) all exhibit low in-plane Young's modulus (25.30–96.09 Nm⁻¹). Notably, four S-XS₂ (X = Si, Ge, Sn, and Pb) monolayers possess negative Poisson's ratios (NPRs). The magnetic and electronic properties vary across the monolayers, with S-ReS₂ and S-OsS₂ being nonmagnetic and metallic, S-MoS₂ being antiferromagnetic and metallic, and S-SiS₂, S-GeS₂, S-SnS₂, S-PbS₂, S-ZrS₂, and S-TiS₂ being nonmagnetic and semiconducting (bandgaps ranged between 1.59 and 2.79 eV). The S-VS₂ monolayer exhibits ferromagnetic half-semiconductor behavior, while S-CrS₂ and S-MnS₂ are ferromagnetic half-metals. The carrier mobilities of the seven semiconducting monolayers range widely (0.20–17 068.47 cm² V⁻¹s⁻¹), and hole mobility could be controlled through uniaxial strains in S-ZrS₂, S-TiS₂, and S-VS₂. Additionally, certain monolayers (S-XS₂ with X = V, Cr, and Mn) have high Curie temperatures and magnetic anisotropy energies. Two semiconducting monolayers (S-XS₂ with X = Si and Ge) are promising candidates for photocatalyzing water splitting, and the metallic or half-metallic S-ReS₂ and S-OsS₂ can boost the electrochemical hydrogen evolution reaction. This work not only adds novel members to the family of 2D materials, but also provides theoretical guidance for further explorations to both experimental and theoretical communities.