Synergistic optical, dielectric and visible-light photocatalytic enhancement in Mo-modified BaTiO₃ nanostructures

Molybdenum-doped barium titanate (BaTiO₃) nanostructures were fabricated by a solid-state reaction and evaluated for simultaneous enhancement of dielectric and optical performance. X-ray diffraction confirmed that progressively higher Mo content drives a tetragonal to cubic phase transformation, evidencing effective lattice tuning. Complementary SEM and EDX analyses showed well-defined grain morphology and uniform elemental distribution, verifying successful Mo incorporation. XPS detected Mo in mixed valence states (Mo³⁺/Mo⁴⁺/Mo⁶⁺) together with Ti³⁺ species, implicating abundant oxygen vacancies that promote charge transport and surface reactivity. Dielectric measurements revealed a marked rise in room-temperature permittivity accompanied by lower loss, indicating improved polarization dynamics. UV-vis diffuse-reflectance spectra displayed a red-shifted absorption edge and a band-gap narrowing from 3.24 eV (pristine BaTiO₃) to 2.92 eV (MBT4), thereby extending visible-light harvesting. All Mo-doped BaTiO₃ samples exhibited notable visible-light photocatalytic performance, with the 3% Mo-doped sample (MBT3) achieving significantly enhanced degradation of Congo red dye under direct sunlight. Notably, MBT3 demonstrated about 90% degradation efficiency within 60 min, compared to the slower response of undoped BaTiO₃, and the corresponding photocatalytic rate constant increased from 0.01754 min^-1 (pure BTO) to 0.03673 min^-1, underscoring the superior reactivity and light-harvesting capability imparted by Mo incorporation. These results demonstrate that Mo incorporation simultaneously tailors BaTiO₃ crystal structure, electronic structure, and dielectric response, positioning the material as a promising multifunctional candidate for sustainable energy and environmental applications.