One-step preparation of halogenated aminobenzonitrile modified g-C3N4 via copolymerization and in situ halogen doping for highly enhanced visible light hydrogen evolution

A series of halogenated aminobenzonitrile modified graphitic carbon nitride (g-C3N4) was prepared by a one-step calcination of dicyandiamide and 2-amino-5-halogen-benzonitriles (X-ABN, X = F, Cl, Br or I, 1.67 wt% of dicyandiamide) together, and named as X-ABN-CN. The resulting X-ABN-CN photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet visible diffuse reflection spectroscopy, and photoluminescence spectroscopy. The characterization results indicated that X-ABN-CN have been successfully prepared, and the it-conjugated system and electronic structure of X-ABN-CN could be improved via copolymerization, Ullmann reaction and in situ halogen doping. Under visible light irradiation (lambda > 400 nm), the photocatalytic activity of X-ABN-CN were much higher than that of pure g-C3N4 and increase with the increase of halogen atomic number. The hydrogen evolution rate of I-ABN-CN (131.4 mu mol h(-1)) was 7.4 times that of g-C3N4 (17.7 mu mol h(-1)). Furthermore, the corresponding mesoporous X-ABN-CN (X-ABN-MCN, X = F, Cl, Br or I) were prepared by using SiO2 nanoparticles as template. As expected, I-ABN-MCN showed the highest photocatalytic activity in all mesoporous samples, which is about 8.8 times that of g-C3N4. The results manifest that the copolymerization, Ullmann reaction, in situ halogen doping and mesoporous structure could be integrated together to modify g-C3N4 by a simple one-step calcination process. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.