Improved thermodynamic stability and visible light absorption in Zr+X codoped (X = S, Se and Te) BaTiO3 photocatalysts: A first-principles study

Band gap tuning of titanium based perovskite oxides through chalcogen doping is an attractive avenue for realizing visible light driven photocatalysis for hydrogen production. Unfortunately, accommodating a chalcogen atom at an O-site of BaTiO ₃ is thermodynamically challenging owing to large differences in the atomic radii and electronegativities of oxygen and chalcogen atoms. In the present study we employ first-principles density functional theory calculations to examine the influence of Zr codoping on the structural, thermodynamic, opto-electronic properties and photocatalytic performance of X-doped (X = S, Se and Te) BaTiO ₃ systems. The atomic structure and energetic properties are computed using SCAN meta-GGA functional of density functional theory, while the electronic and optical properties are computed using the TB-mBJ meta-GGA potential functional. Within the valid limits of the atomic chemical potentials, we find that chalcogen doping in BaTiO ₃ lattice would be experimentally difficult despite a clear reduction in the electronic band gap of this system useful for application in visible light driven photocatalysis. In order to improve the synthesis feasibility of X-doped BaTiO ₃ under oxygen-rich as well as oxygen-poor chemical environments, we propose Zr as a codopant at a Ti-site in X-doped BaTiO ₃ which improves the thermodynamic stability and also retains the reduction in the electronic band gap of cubic BaTiO ₃ caused by the presence of chalcogen atom. Our results suggest that Zr+X (X = S, Se and Te) codoped BaTiO ₃ offer great opportunities as practical photocatalysts for hydrogen production through overall splitting of the water molecule.