Synthesis and characterization of nanocrystalline CuO/ZnO composite powders with enhanced photodegradation performance under sunlight irradiation

Abstract

In the present work, the sol–gel auto-combustion method has been used to synthesize nanocrystalline copper-zinc oxide composite powders with different weight ratios using diethanolamine (DEA) as fuel. The structural, morphological, optical, and magnetic properties including the local atomic structure of each calcined sample were systematically characterized by means of XRD, SEM, UV-DRS, VSM, and synchrotron XANES measurements. The XRD results revealed the complete formation of CuO/ZnO nanocomposites, composed of monoclinic CuO and hexagonal wurtzite ZnO structures without any impurity phases. The observation of XANES spectra confirms that both Zn and Cu ions in all samples exhibit only fourfold coordination with oxygen atoms. UV-DRS analysis demonstrated that CuO-rich composites exhibited strong absorption in visible light with moderate infrared reflection efficiency as compared to the pure ZnO sample, but ZnO-rich composites show distinctive absorption in infrared region. According to magnetic measurements, both paramagnetism and ferromagnetism can simultaneously arise as the CuO content increases within the CuO/ZnO composites. The photocatalytic activity of CuO/ZnO composites was evaluated by the decomposition of four types of pollutants: phenol rhodamine B (RhB), heteropolyaromatic methylene blue (MB), azoic methyl orange (MO), and methyl red (MR) under sunlight irradiation. In comparison with pure ZnO, those CuO/ZnO samples for which the ratio has been optimized exhibit enhanced photocatalytic degradation in all organic dyes, reaching 90–96% within a period of 150 min. From these results, it can be argued that CuO/ZnO composites show considerable potential for the harvesting of solar energy as well as environmental remediation.