Effect of carbon-dots modification on the structure and photocatalytic activity of g-C3N4

As a promising metal-free photocatalyst, graphitic carbon nitride (g-C3N4) has attracted increasing attention. However, from the viewpoint of practical application, the quantum efficiency of g-C3N4 needs to be further improved. In this article, carbon dots (C-dots) modified g-C3N4 hybrid was successfully prepared by a novel strategy using C-dots and dicyandiamide as starting materials. The photocatalyst was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectrum (DRS), X-ray photoelectron spectroscopy (XPS), powder photoluminescence (PL) and surface photovoltage spectrum (SPS). Both the photocatalytic activity of C-dots modified g-C3N4 was evaluated by degradation of Rhodamine B under UV irradiation and photocatalytic hydrogen production under visible irradiation. The experimental results show that C dots modification causes the lattice distortion of g-C3N4. With increase in the loading amount of C-dots, the photocatalytic activity of g-C3N4 increase first and then decrease. g-C3N4 modified with 0.25 wt.% C-dots shows the highest photocatalytic activity, which is 3 times higher than pristine g-C3N4. C-dots act as electron-sinks, which prevent the recombination of photo-generated electron-hole pairs, enhancing the photocatalytic activity of g-C3N4. However, too much C-dots become recombination centers, which is detrimental to the photocatalytic activity of g-C3N4. (C) 2015 Elsevier B.V. All rights reserved.