Nature-Mimic Method To Fabricate Polydopamine/Graphitic Carbon Nitride for Enhancing Photocatalytic Degradation Performance

In this paper, polydopamine/graphitic carbon nitride (PDA/g-C₃N₄) has been synthesized by the dopamine (DA) polymerization modification of the surface of g-C₃N₄. For a study of the morphology and optical property of catalysts, the obtained PDA/g-C₃N₄ composites were characterized by FTIR, XRD, SEM, TEM, BET, XPS, TGA, DRS (diffuse reflectance spectroscopy), photoluminescence, and photocurrent generation. Polydopamine (PDA) plays multiple roles as a light absorption substance, an electron transfer acceptor, and an adhesive interface in the design of PDA/g-C₃N₄ photosynthetic systems. The optical results demonstrate that PDA has an effect on the PDA/g-C₃N₄ composite light-harvesting capacity. With an increasing PDA ratio, the photocatalyst’s light-harvesting ability was gradually improved. In addition, the 10%PDA/g-C₃N₄ composite has been shown to be highly efficient for the degradation of the organic dyes methylene blue (MB), Rhodamine B (RhB), and phenol under visible-light irradiation. The degradation efficiency of MB is about 98% in 3 h, and the catalysts can have a degradation efficiency higher than 90% after four cycles. Polydopamine (PDA), as a surface-modified additive with abundant semiquinone and quinone functional ligands, was introduced for an improvement of the transfer ability of photoinduced electrons and accepts them from a semiconductor-based photocatalysis material (g-C₃N₄), which can reduce electron–hole recombination of g-C₃N₄ and enhance the photocatalytic activity.