Structural, optical, and photocatalytic performance of Sr-site (Nd) and Ti-site (Ni) Doped SrTiO₃ for Methylene Blue Degradation

Strontium Titanate ( SrTiO3 or STO ) is a perovskite semiconductor extensively studied for photocatalytic applications, particularly in methylene blue (MB) degradation from wastewater. Its photocatalytic performance can be enhanced by site-specific doping either at the A-site ( Sr ) and/or B-site (Ti) of the perovskite lattice. Here, pure, Ni-doped, and Nd-doped STO photocatalysts (SrTi_1−xNi_xO_3 and Sr_1−xNd_xTiO_3; x = 0.05) were successfully fabricated via the coprecipitation technique. Structural, vibrational, and optical properties were characterized by X-ray diffraction (XRD), Fourier Transform infrared (FTIR), UV-Vis diffuse reflectance spectra (DRS), and UV-Vis spectroscopy instruments. The cubic SrTiO_3 perovskite phase was achieved in all samples, where both Ni and Nd doping enlarged the crystallite sizes of STO. The success of photocatalyst formation was also confirmed by emerging FTIR spectra at about 570 cm^−1, corresponding to Sr -Ti-O vibrations. DRS analysis revealed a bandgap of 3.23 eV for STO, which widened to 3.55 eV upon Ni doping, while Nd doping narrowed it slightly to 3.17 eV. The photocatalytic activity was evaluated by measuring the degradation of MB under UV light. Nd-doped STO revealed the highest photocatalytic performance, achieving a degradation efficiency of 52%. These findings highlight the distinct roles of Sr-site and Ti-site dopants in modifying the structural and optical properties of STO, which directly influence its photocatalytic activity.