Application of CuO and its composite with polyaniline on the photocatalytic degradation of methylene blue and the Cr(VI) photoreduction under visible light

Copper oxide (CuO) as the photocatalyst nanoparticle was prepared by the solution combustion technique. During the synthesis, iron atom source, which was iron nitrate, was added to the reaction medium to obtain iron doped CuO nanoparticles. In addition, the iron doped CuO nanoparticles were combined with the conducting polymer, which was polyaniline, through the in-situ polymerization technique. The chemical and crystal structure, optical property and the photocatalytic activity of the CuO nanoparticles and their composites were studied as a function the dopant atom concentration of CuO and the photocatalyst composition of the composites. The prepared samples were characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, fluorescence spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray (EDX) spectroscopy and UV-Vis absorption spectroscopy. The photocatalytic activity of the prepared samples was evaluated by the photocatalytic degradation of a model dye, methylene blue, under visible light irradiation. In addition, the Cr(VI) photoreduction efficiency of the prepared samples were studied. Iron atoms might enter into the substitutional sites of CuO. The iron atoms might act as a trapping center to capture the photoinduced charge carriers of CuO, promoting both the charge separation and the photocatalytic activities. The photocatalytic dye degradation efficiency and the Cr(VI) photoreduction efficiency of the iron doped CuO increased by almost 17% compared to undoped CuO. The composites with low polyaniline content might promote the charge separation because of the difference between the band potentials of CuO and polyaniline as shown in the graphical abstract. The composite with 80 wt.% of the iron doped CuO exhibited the highest photocatalytic dye degradation of almost 72% and the Cr(VI) photoreduction efficiency of almost 56%.