Cupric Oxide Nanoleaves for the Oxidative Degradation of Methyl Orange without Heating or Light

Low-cost 2D cupric oxide nanoleaves (CuO NLs) are straightforwardly synthesized at room temperature by precipitation varying the addition method of the alkali. No further treatments are necessary to obtain high purity NLs. The effect of the different addition methods of alkali on the morphological, structural, vibrational, and optical properties is studied by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) and ultraviolet–visible (UV–vis) spectroscopies. NLs grown by alkali addition in a dropwise manner are on average 281, 178, and 17 nm long, wide, and thick, respectively, and composed of crystallites of 14 nm corresponding to the crystallographic planes (1̅11)/(002) and (111)/(200). NLs obtained by this method agglomerate forming flower-like nanostructures, exhibiting indirect band gap energy of 1.21 eV. NLs grown by alkali addition in a one-step manner are on average significantly bigger, being 602, 219, and 26 nm long, wide, and thick, respectively, composed of crystallites of 19 and 16 nm corresponding to the crystallographic planes (1̅11)/(002) and (111)/(200), respectively. These NLs agglomerate randomly with no predominant form observed, exhibiting indirect band gap energy of 1.39 eV. The addition method of alkali does not influence the average crystallite size of NLs, whereas the microstrain distribution is sensitive to the initial concentration of OH– ions. Our results suggest that an indirect electronic transition between the valence and conduction bands might be more feasible than a direct one. NLs grown by the one-step method present the highest efficiency as catalyst toward catalytic oxidative degradation of the methyl orange dye with no heating and without the influence of light. Finally, this catalyst is easily recycled several times preserving its high catalytic activity.