ZnO-Layered Double Hydroxide@Graphitic Carbon Nitride Composite for Consecutive Adsorption and Photodegradation of Dyes under UV and Visible Lights

In this work, a ZnO-layered double hydroxide@graphitic carbon nitride composite (ZnO-LDH@C(3)N(4)) was synthesized via co-precipitation method with solvothermal treatment. The structure and morphology of ZnO-LDH@C(3)N(4) composite were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopes/transmission electron microscopes (SEM/TEM), N(2) adsorption/desorption, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis-DRS), photoluminescence spectrometer (PL) and electrochemical impedance spectroscopy (EIS). The adsorption and photocatalytic properties of ZnO-LDH@C(3)N(4) composite towards the organic dyes: Orange II sodium salt (OrgII, an anionic azo dye) and methylene blue (MB, a cationic azo dye) were investigated. Compared to ZnO-LDH and g-C(3)N(4), the ZnO-LDH@C(3)N(4) composite displayed an excellent performance in both adsorption and photocatalytic degradation of the organic dyes. Moreover, a combination of ZnO-LDH and g-C(3)N(4) significantly improved the photocatalytic performance of ZnO-LDH and g-C(3)N(4) under visible-light irradiation. The adsorption and photocatalytic mechanism were also investigated.