An improved photocatalytic activity of Graphitic carbon nitride (CN) photocatalyst was achieved by incorporating Cu2+ into CN in the presence of hyperbranched polyethylene amine (HPEI) as a capping agent. The addition of Cu to CN (CNHPEI+Cu) increased the photocatalytic degradation efficiency of wastewater dye pollutant methylene blue (MB) from 42 % to 95 %. E. coli and MS2 performed best in terms of inactivation to CNHPEI+Cu, achieving 5.5 ± 0.3 and 5.3 ± 0.1 log inactivation after 60 min of exposure, respectively. Excellent catalyst reusability and photocatalytic activity for MB in various types were obtained. To investigate the photocatalyst structure, morphology, optical, and photoelectric properties, we used X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and photocatalytic activity. It was found through XRD and XPS that the prepared photocatalysts were made up of Cu-doped CN and that the valence state of Cu was Cu0. Under the visible part of the solar spectrum (>400 nm), the N2 adsorption-desorption isotherms of pure CN, CNHPEI, and CNHPEI+Cu showed that copper did not alter the microstructure of pure CN. The photocatalytic activity of CNHPEI+Cu was improved by incorporating Cu0 into CN, as this reduces the rate of electron-hole recombination in pure CN and accelerates the separation of electron-hole pairs. Electron spin resonance (ESR) spin trap experiments on the production of reactive oxygen species (ROS) from CNHPEI+Cu under visible light indicate that the presence of superoxide radicals (O2•−), hydroxyl radicals (•OH) and holes could enhance the photocatalytic activity of the material.
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