Fabrication of Reduced Band Gap Copper Oxide Photocatalysts with Enhanced Dye Degradation under Visible Light

The copper oxide (CuO) and CuO doped with bismuth (Bi-CuO) nanoparticles (NPs) were synthesized using the co-precipitation technique. The crystalline structure of CuO was confirmed by x-ray diffraction (XRD), and the metal oxide band was confirmed using the Fourier-transform infrared (FTIR) spectroscopy. The crystallite size of CuO calculated from XRD was 18.11 nm and that of Bi-CuO was 14.82 nm. The Bi-CuO NPs having band gap (Eg) reduced to 1.9 eV were synthesized by doping CuO (Eg 2.2 eV) with Bi. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the morphology and particle sizes. The decomposition of the precursor to CuO was confirmed using the thermal gravimetric analysis (TGA). The chemical structure of indigo carmine (IC) dye degradation products was explained by performing the liquid chromatography-mass spectrometry (LC-MASS) of dye and its degraded products. The indigo carmine (IC) dye was degraded 97.05% and 84.12% by Bi-CuO and CuO, respectively, under visible light within 120 min. The optimized conditions for achieving maximum degradation efficiency of the dye were pH (4), an initial concentration of dye (10 ppm), the dosage of catalysts (15 mg) and a temperature of 30 °C.