Urea and Melamine Formaldehyde Resin-Derived Tubular g-C3N4 with Highly Efficient Photocatalytic Performance.

Construction of various nanostructure g-C3N4, especially those with a tubular structure, is gaining considerable research interest because of their large specific surface area, high carrier transport efficiency, and excellent mass transfer. In this study, a novel multistage tubular g-C3N4 (TCN) has been prepared by the copolymerization of melamine formaldehyde (MF) resin with urea. With the introduction of MF resin, the electrostructure of TCN and its hydrophilicity property have been obviously ameliorated, thereby enhancing its visible-light absorption and improving the interface contact between TCN and water. Moreover, photocurrent response and electrochemical impedance spectra indicate that the special multistage tubular structure facilitates the spatial charge transfer and photogenerated carrier separation. Thus, the as-prepared TCN exhibits excellent photoactivities under visible-light irradiation. Among the samples, TCN-0.1 shows the best performance. Its hydrogen evolution rate is approximately 7505 μmol·g-1·h-1, which is 6.05 times greater than that of g-C3N4 (prepared by urea at 600 °C), and its apparent quantum efficiency is nearly 19.2% at 400 nm. In addition, TCN is also endowed with outstanding visible-light performance and durability for the degradation of tetracycline and methyl orange. This work might provide a significant inspiration for the design of new, highly efficient g-C3N4-based materials and further deepen our understanding of the preparation of tubular photocatalysts.