Investigation of Cobalt Substitution on the Structural, Optical Band Gap, and Photocatalytic Dye Degradation Properties of Spray Deposited SnO2Thin Films

Pure and cobalt substituted tin oxide thin films are successfully formed on a glass substrate using the simple spray pyrolysis technique. XRD patterns reveal the polycrystalline nature of the samples with tetragonal rutile structure. The shift in X-ray diffraction peak to a higher 2θ value and its subsequent contraction of the SnO2 rutile lattice along the c-axis manifests the infusion of the guest cobalt ions. Crystallite size and microstrain values are found to vary with cobalt substitution. SEM analysis shows the uniform dispersion of the nanoparticles in the prepared thin films. The optical band gap values are found to narrow down with cobalt substitution from 4.04 eV–3.93 eV. Photoluminescence study hints at the presence of intermediate states within the forbidden energy band gap of SnO2. Photocatalytic dye degradation of Methylene blue (MB) highlights the role of cobalt with a high photocatalytic activity of 86 % compared to other investigated thin films.