Fabrication of efficient visible light activated Cu–P25–graphene ternary composite for photocatalytic degradation of methyl blue

Abstract Cu–P25–graphene nanocomposite was fabricated through hydrothermal method at relatively low temperature. The technique used is P25–graphene (PG) binary composite was firstly prepared by P25 and graphite oxide (GO), and then Cu 2+ ions were impregnated into PG composite. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. As the results showed, the Cu–P25–graphene (CPG) nanocomposites possessed the extended light absorption in visible light and better charge separation capability as compared to the pure P25 and PG system. Moreover, CPG-4 (4 mM Cu(NO 3 ) 2 ) showed the highest degradation rate of methyl blue (MB) under the visible light, which the removal efficiency can reach 98% after 100 min. The corresponding hydrogen evolution rate of CPG-4 was 7.9 times than pure P25. It was concluded that the synergistic effects of Cu 2+ ions and graphene narrowed the band gap of TiO 2 and promoted charge separation, which played significant roles for the enhancement of photoactivity of CPG composite catalysts. In addition, it was observed that the photodegradation of MB followed the first order reaction kinetics. The effects of pH values of MB solution for photocatalysts had also been investigated. The result confirmed that the optimum values of pH were found to be 7. Finally, the stability test of photocatalysts was carried out and the photocatalytic mechanism was explained concretely.