A comparative first-principles investigation of bilayer NbOX2 (X=Cl, Br, I) for Photocatalytic water splitting applications

Abstract

Motivated by our previous work on bulk NbOX2 , where we have reported its high 1dielectric polarisation and finite piezoelectric response, this work extends to its 2D homo bilayer system to explore its potential for photocatalytic water splitting. Herein, density functional theory (DFT) were employed in probing the structural, electronic, optical, and photocatalytic properties of 2D homo bilayer NbOX2 (X = Cl, Br, and I). Our results show that structurally, NbOCl2 and NbOBr2 prefer AC bilayer stacking,while AB stacking was preferred by NbOI2 . All the considered bilayers are dynamically, thermally, and mechanically stable. From the analysis of electronic structure we have found a decreasing trend in the energy band gap as X goes down the group from Cl to I, with the position of the valence band maximum shifting upward along the high symmetry points. In terms of carrier mobility, all 2D bilayer systems possess high carrier mobility comparable to known 2D materials. It also exhibits an anisotropic carrier transfer property by which charge carriers are separated efficiently. These materials show similar trends to BiOI and PtSe2 , in which photocatalytic efficiency was increased by forming the multiple layers. The materials under investigation are suitable for photocatalytic water splitting under visible and ultraviolet regions with absorption coefficients of 105 cm-1.