Structural, optical and photocatalytic studies of trimetallic oxides nanostructures prepared via wet chemical approach

Multi metal based photocatalyst (CdO-MgO-Fe2O3) was synthesized via wet chemical approach i.e. co-precipitation method. The single transition metal oxides like CdO, MgO and Fe2O3 were also prepared for comparative studies. Structural elucidation of all prepared powder catalysts (CdO, MgO, Fe2O3 and CdO-MgO-Fe2O3) was conducted by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). XRD showed the presence of the MgO (cubic) - Fe2O3 (rhombohedral)- CdO (cubic) phase with an average crystallite size of MgO (9 nm), Fe2O3 (12 nm), CdO (23 nm). FTIR proved the existence of Mg-O, Fe-2-O-3 and Cd-O by distinctive vibrational bands at 772 cm(-1), 581 cm(-1) and 480 cm(-1) respectively. UV-vis spectral studies showed that the bandgap for CdO-MgO-Fe2O3 nanocomposite was 1.76 eV which made it an efficient photocatalyst for use both in the UV and visible regions. Two probe I-V measurements confirmed the pure semiconducting behavior and possible formation of heterojunction in the CdO-MgO-Fe2O3 nanocomposite. The photocatalytic performance of the CdO-MgO-Fe2O3 nanocomposite with equal metal ion concentration of Mg, Fe and Cd at different pH values was explored by visible light illumination on methylene blue (MB) dye as a standard organic pollutant. The CdO-MgO-Fe2O3 nanocomposite with metal ion ratio 1:1:1 in an alkaline medium showed the maximum photocatalytic performance. The rate constant (kMB) value for the degradation of MB was similar to 0.0820 min(-1). The photocatalytic activity has been improved due to the effective decrease in the recombination rate of charge carriers. The possible mechanism for improvement of the photocatalytic performance using visible light illumination has also been suggested and discussed.