DFT Study of Methylene Blue Adsorption on ZnTiO₃ and TiO₂ Surfaces (101)

The search for alternative materials with high dye adsorption capacity, such as methylene blue (MB), remains the focus of current studies. This computational study focuses on oxides ZnTiO₃ and TiO₂ (anatase phase) and on their adsorptive properties. Computational calculations based on DFT methods were performed using the Viena Ab initio Simulation Package (VASP) code to study the electronic properties of these oxides. The bandgap energy values calculated by the Hubbard U (GGA + U) method for ZnTiO₃ and TiO₂ were 3.17 and 3.21 eV, respectively, which are consistent with the experimental data. The most favorable orientation of the MB adsorbed on the surface (101) of both oxides is semi-perpendicular. Stronger adsorption was observed on the ZnTiO₃ surface (-282.05 kJ/mol) than on TiO₂ (-10.95 kJ/mol). Anchoring of the MB molecule on both surfaces was carried out by means of two protons in a bidentate chelating (BC) adsorption model. The high adsorption energy of the MB dye on the ZnTiO₃ surface shows the potential value of using this mixed oxide as a dye adsorbent for several technological and environmental applications.