CuO/ZnO/g-C3N4 heterostructures as efficient visible light-driven photocatalysts

[Display omitted] •Direct Z-scheme CuO/ZnO/g-C3N4 heterostrurcture has been fabricated for the first time.•The prepared heterostructure has a mixture of two morphologies, nanoparticles and flowers composed of nanosheets.•CuO/ZnO/g-C3N4 heterostrurcture exhibits higher photocatalytic activity than CuO/ZnO heterostrurcture. Photocatalytic degradation of organic pollutants is an environmentally friendly technique for water treatment. In this work, CuO/ZnO/g-C3N4 heterostructure is prepared via solution combustion route to take advantage of the porous structure which is resulted from releasing the gases during the combustion. XRD, EDX, TEM, XPS, and TEM analyses confirm the successful construction of CuO/ZnO/g-C3N4 heterostructure. SEM images reveal that the as-prepared heterostructure consists of flower-like nanosheets decorated with nanoparticles. The CuO/ZnO/g-C3N4 heterostructure exhibits improved photocatalytic activity for methylene blue (MB) degradation in comparison to the CuO/ZnO system under visible light irradiation. At optimal experimental conditions, about 98% of MB is degraded within 45 min. Moreover, about 91% of ammonia- nitrogen is degraded after 6 h visible light illumination. The enhanced photocatalytic activity is attributed to the improved redox potential of the photocatalyst and efficient electrons and holes separation induced by the Z-scheme charge carrier transfer.