Visible-light-induced dye degradation over copper-modified reduced graphene oxide.

Previously, it was found that reduced graphene oxide (RGO) can degrade rhodamine B (RhB) under visible-light irradiation, but with an extraordinarily slow rate. It was also found that modification of RGO with gold nanoparticles can dramatically accelerate the photoreaction rate. Herein, we describe the preparation and photocatalytic properties of copper-ion-modified RGO composite materials, which display a faster photocatalytic reaction rate and better mineralization under visible-light irradiation than gold-modified RGO. The copper-ion-modified RGO composites were prepared by an immersion method. The characterization results of X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy show the presence of crystalline copper species Cu(2)(OH)(3)NO(3) and Cu(2)(OH)(3)Cl on the surface of RGO. Modification of RGO with the copper species greatly enhances the degradation of RhB--after 3 hours of reaction under visible-light irradiation, the total organic carbon is decreased by about 31%. The copper species act as an electron relay, passing the excited electrons from the RGO sheets to adsorbed oxygen, thus leading to continuous generation of reactive oxygen species for the degradation of RhB.