First-principles investigations on the conducting photocatalytic behaviour in SrZr_xGe_1−xO₃ (x = 1, 0.96, 0.92 and 0.88)

Strontium Zirconate (SrZrO₃) is a well-known perovskite-type material that has generated significant interest in materials research due to its unique structural and functional features. In addition, it has appeared as a potential photocatalyst in the realm of environmental remediation and energy conversion. The electronic structure and structural geometry of the SrZrO₃ crystal were computed employing the five functionals of GGA, including GGA with PBE, GGA with RPBE, GGA with PW91, GGA with WC, and GGA with PBEsol, as well as DFT + U using by computational approaches. Next, to improve the photocatalytic activity with reduced band gap, the doping by 4%, 8%, and 12% of Ge atoms in substituting Zr atoms has the empirical formula: SrZr_0.96Ge_0.04O₃, SrZr_0.92Ge_0.08O₃ and SrZr_0.88Ge_0.12O₃, respectively. Secondly, GGA with PBE method conveyed almost overlapping band gap (3.72 eV) with the experimental value at 3.72 eV for standard, SrZrO₃ crystal. As a result, it was used for calculation of the density of state (DOS), the partial density of state (PDOS), and optical properties. At last, the absorption ability regarding their photocatalytic activity against methylene blue (MB) dye was assessed and calculated. First of all, the band gaps by the most accurate method of GGA with PBE are at 3.72, 2.43, 2.18, and 1.20 eV for SrZrO₃, SrZr_0.96Ge_0.04O₃, SrZr_0.92Ge_0.08O₃ and SrZr_0.88Ge_0.12O₃, respectively. Secondly, having the sharp peak for all crystals in valence band (VB), they are considered as p-type semiconductor materials, creating holes in the VB thereby enabling more hydroxyl free radical for photocatalysis. Doping showed no effect on absorbance at photon energies greater than 4.0 eV, but it can have an effect at lower photon energies, which is more supportive of band gap or electronic structure. In case of absorption, SrZr_0.88Ge_0.12O₃ illustrates the highest photocatalytic activity against MB dye, and have a larger surface energy.