Mo doping-induced band gap narrowing and improved photocatalytic efficiency of La₀.₉Sr₁.₁CoO₄ layered perovskites for organic dye degradation

Layered perovskite oxides are promising materials for photocatalytic applications; however, their photocatalytic efficiency is often limited by wide band gaps and rapid charge recombination. In this study, the photocatalytic performance of Mo doped La0.9Sr1.1CoO4 layered perovskites for the degradation of methyl orange was investigated under UV irradiation, for the first time. Nanopowders of La0.9Sr1.1Co1−xMoxO4 (x = 0, 0.05 and 0.1) were successfully synthesized using a modified sol-gel route. The structural properties, morphology and lattice dynamics of the synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy, respectively. The structural analysis confirmed a tetragonal structure with the I4/mmm space group for all samples. UV-Vis spectroscopy showed a reduction in the optical band gap energy of Mo doped La0.9Sr1.1CoO4 from 3.6 eV (x = 0) to 2.9 eV (x = 0.1). Photocatalytic degradation of methyl orange revealed that the Mo-doped samples achieved higher efficiency (80%) compared with the undoped sample (37%). In addition, the nonlinear optical absorption of the synthesized powders was investigated using open-aperture Z-scan technique. All samples exhibited a positive nonlinear refractive index related to the self-focusing effect. The nonlinear refractive index and nonlinear absorption coefficients of Mo doped specimens were obtained in order of $$\:{10}^{-10}(c{m}^{2}/W)$$ and $$\:{10}^{-6}\left(\frac{cm}{W}\right)$$, respectively.