Facile synthesis of self-assembled hollow g-C3N4 microtubes for the efficient high-performance photocatalytic degradation of hazardous pollutants under LED light illumination

Abstract

Fabricating environmentally friendly tubular g-C₃N₄ still remains challenging. We report the synthesis of g-C₃N₄ microtubes using a hydrothermal method in a water–ethanol system. Initially, g-C₃N₄ was obtained as a white complex with a rod-shaped morphology, which upon further calcination yielded a hollow microtube of g-C₃N₄ due to the generation of NH₃ in the system. We systematically explained the formation mechanism of these hollow microtubes with the help of FESEM and TEM images. The photocatalytic performances of the as-synthesized g-C₃N₄ microrods were studied through the degradation of rhodamine B (RhB) using all the as-prepared CN_X photocatalysts and the degradation of tetracycline (TC) antibiotic using the as-prepared CN_12 photocatalyst under LED light irradiation. More than 80% degradation was observed for both RhB dye and TC antibiotic. The efficiencies were found to be much higher than those of bulk g-C₃N₄. CN_12 exhibited the maximum degradation rate constant (k) of 0.0413 min⁻¹ for RhB and 0.01794 min⁻¹ for TC, which were relatively higher than those of pristine b-CN (0.0063/0.00235 min⁻¹, respectively). The trapping experiments showed that superoxide radical anions (˙O₂⁻) were the main reactive species, while holes (h⁺) played a secondary role; there was also a negligible contribution from hydroxyl radicals (˙OH) in the photocatalytic degradation of TC using the microrods. Further, the high-performance degradation mechanism under visible-light was explained. This work provides guidance for designing high-performance photocatalysts with tunable morphology by a self-assembly mechanism.