XSnS3 (X = Ga, In) monolayer semiconductors as photo-catalysts for water splitting: a first principles study

Abstract

Considering the growth of global population, energy requirements and industrialization, and acceleration of the global warming issue, finding new clean energy resources is necessary for the sustainability of civilization. Pure hydrogen is considered as a new possible source of clean energy that promises to reduce carbon emissions. In this regard, photocatalytic water splitting is a promising approach that can be employed for the production of hydrogen. In this paper, using first principles calculations based on the density functional theory (DFT), two novel two-dimensional (2D) monolayer materials named 2D XSnS₃ (X = Ga, In) monolayers with promise for water-splitting applications are predicted. After confirming their stability, their electrical and optical features were assessed. By using the hybrid functional level of theory, it was found that these two predicted materials are semiconductors showing moderate indirect band gaps of 1.38 and 1.68 eV for GaSnS₃ and InSnS₃, respectively. Our optical properties investigation shows that the proposed monolayers exhibit good absorption properties in the visible region. Moreover, it is found that both electrical and optical characteristics of these predicted 2D materials can be functionally adjusted by strain and, interestingly, an indirect–direct band gap transition occurs under compression strain. Considering their moderate band gaps and good absorption in the visible region, we further computed the absolute band edge positions and Gibb's free energy for hydrogen adsorption of the materials and it was found that the 2D InSnS₃ monolayer is a promising material for water splitting applications.