Predicting A New Quaternary Photocatalyst Suitable For PEC Process To Produce Hydrogen And Determnation of Its Structural, Electronics, And Optical Properties Using Density Functional Theory

Abstract

Our present work represents a comprehensive theoretical and computational research in quest for predicting new photocatalysts suitable for photoelectrochemical process (PEC) to produce hydrogen by splitting water. We predict a new photocatalyst, CuBiW₂O₈ that exhibits some promising photocatalytic features seemed elusive to date. It is well known that all physical properties are calculated once ground state structure is known. However, knowing crystal structure is extremely challenging and was considered unpredictable before the material is synthesized. Our density functional theory (DFT) determines the crystal structure of CuBiW₂O₈ to be monoclinic which was later found energetically equivalent to its experimental counterpart. In addition to structure determination, we calculate the electronic and optical properties of CuBiW₂O₈ for the first time. Our calculated band gap is 1.43 eV that validates the approach to make band engineering successful by forming suitable complex oxides. The band structure calculation also reveals that CuBiW2O possesses indirect band gap. Moreover, density of states (DOS) calculation demonstrates a successful band gap reduction approach with respect to binary and ternary oxides such as TiO₂, WO₃, BiW₂O₉ etc., where Cu 3d orbital plays a major role in band gap reduction. In addition, it explains why electron transition from valence band to conduction band is possible although both band edges are mostly dominated by d orbitals and d-d electron transition is forbidden. Finally, our optical calculation determines this material is optically anisotropic and has a high absorption rate that facilitates hydrogen production through photo-excitations.