g-C3N4/Ag/GO Composite Photocatalyst with Efficient Photocatalytic Performance: Synthesis, Characterization, Kinetic Studies, Toxicity Assessment and Degradation Mechanism

The g-C3N4/Ag/GO (CNAG) photocatalysts were synthesized by a facile two-step reaction route. The as-prepared CNAG samples were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and ultraviolet-visible diffuse reflectance spectroscopy techniques (UV-vis DRS). The photocatalytic activity was obtained by degrading rhodamine B (RhB) under simulated sunlight and the results showed that photocatalytic activity of CNAG was much higher than that of pure g-C3N4 and g-C3N4/Ag. When the mass ratio of GO was 6%, the as-prepared CNAG-6% sample possessed the highest photocatalytic activity and the kinetic constant of RhB degradation was 0.077 min(-1), which was almost 4.3 times higher than that of pure g-C3N4 (0.018 min(-1)) and 2.5 times higher than that of the g-C3N4/Ag (0.031 min(-1)) composite, respectively. The toxicity of CNAG samples was assessed via seed germination experiment and no significant inhibitory effect was observed. The enhanced photocatalytic activity could be attributed to the synergistic effect of partial surface plasma resonance (SPR) effect of Ag, strong visible light absorption and the high separation efficiency of photon-generated carrier. The CNAG-6% sample exhibited excellent stability during the cycle experiment. Finally, a possible photocatalytic mechanism was proposed.