**Yohannes Teklemariam Gaim \*, Gebrekidan Mebrahtu Tesfamariam, Gebretinsae Yeabyo Nigussie and Mengstu Etay Ashebir**

Department of Chemistry, College of Natural and Computational Sciences, Mekelle University, Mekelle P.O.Box: 231, Ethiopia; gebrekidanmebrahtu11102007@gmail.com (G.M.T.); g.tinsae21@gmail.com (G.Y.N.); mengstu.etay@mu.edu.et (M.E.A.)

**\*** Correspondence: yohannesteklemariam1@gmail.com; Tel.: +25-19-3203-4081

Received: 19 September 2019; Accepted: 14 October 2019; Published: 16 October 2019

**Abstract:** In this study, a N-doped Cu2O/ZnO nanocomposite was prepared by a co-precipitation and thermal decomposition technique from CuCl2, 2H2O, ZnSO4, 7H2O and CO(NH2)2 as precursors. The as-synthesized nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared analysis (FT–IR) and an ultraviolet–visible (UV–Vis) reflectance spectrometer. From the XRD diffractogram of N-doped Cu2O/ZnO nanocomposite, cubic and hexagonal wurtzite crystal structures of Cu2O, and ZnO, respectively were identified. The UV-vis reflectance spectra illustrated that the absorption edge of N-doped Cu2O/ZnO nanocomposite is more extended to the longer wavelength than ZnO, Cu2O and Cu2O/ZnO nanomaterials. FT–IR bands confirmed the presence of ZnO, Cu2O, and nitrogen in the N-doped Cu2O/ZnO nanocomposite. Photocatalytic activity of the as-synthesized nanocomposite was tested for methyl red degradation using sunlight as an energy source by optimizing the concentration of the dye and amount of the catalyst loaded. The degradation efficiency was greater in N-doped Cu2O/ZnO nanocomposite as compared to ZnO, Cu2O and Cu2O/ZnO nanomaterials. This is due to the coupling of the semiconductors which increases the absorption and exploitation capability of solar light and increases the charge separation as well. Besides that, nitrogen doping can extend absorption of light to the visible region by decreasing the energy gap. Therefore, N-doped Cu2O/ZnO nanocomposite is a solar light-active photocatalyst which can be used in the degradation of organic pollutants.

**Keywords:** photocatalyst; nanocomposite; dye degradation; co-precipitation
