Materials Chemistry and Physics 256 (2020) 123754 Available online 25 August 2020 0254-0584/© 2020 Elsevier B.V. All rights reserved. Remarkable photocatalytic activity of Zr doped ZnO and ZrO 2 /ZnO nanocomposites: Structural, morphological and photoluminescence properties Mohammed Ahmed Wahba , Saad Mabrouk Yakout * , Walied A.A. Mohamed , Hoda R. Galal Inorganic Chemistry Department, National Research Centre (NRC), El Buhouth St., Dokki, Cairo, 12622, Egypt HIGHLIGHTS G R A P H I C A L ABSTRACT • Zr doped ZnO and ZrO 2 /ZnO nano- composites were prepared by sol gel method. • Increasing ZrO 2 concentration enhances the photocatalytic of ZnO. • ZrO 2 /ZnO (1:1) composite exhibits su- perior photocatalytic activity. • Hydroxyl radicals have active role in photodegradation. A R T I C L E INFO Keywords: ZnO/ZrO 2 nanocomposites Photocatalysis Organic dyes Methylene blue Indigo carmine ABSTRACT Industrial effuents containing synthetic organic dyes impose a signifcant level of threatening to the environment and to the health of living organisms. In the context to develop active materials able to degrade synthetic textile dyes, we report highly effcient photocatalysts composed of Zr doped ZnO and ZrO 2 /ZnO heterostructures syn- thesized via modifed sol-gel Pechini method. The crystal structure, morphology and the optical properties of the synthesized powders were characterized using XRD, Rietveld refnement, SEM, EDX and diffuse refectance. A single phase of ZnO hexagonal structure was found in pure and 5 wt% Zr doped ZnO, whereas multi-phases consist of hexagonal ZnO plus either tetragonal or monoclinic ZrO 2 were detected using higher concentrations of Zr (10–50 wt %). Pure ZnO shows nanospherical-shaped particles with average size of 36 nm ZrO 2 /ZnO nanocomposites with ZrO 2 content of 30, 40 and 50 wt% show similar spherical grains with homogeneous particle size distribution. EDX spectrum of ZrO 2 /ZnO nanocomposite confrms the existence of Zn, Zr and O elements and the absence of any impurities. ZrO 2 /ZnO nanocomposites exhibit two band gaps related to their individual components. The results of photocatalytic experiments revealed that both Zr doped ZnO and ZrO 2 /ZnO nanocomposites demonstrate remarkable photocatalytic activities for indigo carmine (IC) and methylene blue (MB) degradation. The highest degradation rate was realized by ZrO 2 /ZnO (50:50) nanocomposite with degradation effciencies of 99% and 97% for IC and MB in 300 and 150 min, respectively. The superior activity of ZrO 2 /ZnO nanocomposite was attributed to the increases in the charge separation due to strong interfacial surface interaction. The fuorescence studies based on conversion of coumarin to 7-hydroxycoumarin showed similar results to the photocatalytic activity and proved the effective role of the hydroxyl radicals in the degradation process. * Corresponding author. E-mail address: s_mabrok2002@yahoo.com (S.M. Yakout). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys https://doi.org/10.1016/j.matchemphys.2020.123754 Received 13 April 2020; Received in revised form 29 June 2020; Accepted 20 August 2020