Metal-free in situ carbon-nanotube-modified mesoporous graphitic carbon nitride nanocomposite with enhanced visible light photocatalytic performance

We synthesized a metal-free photocatalyst comprising mesoporous carbon nitride (mpg-C3N4) and carbon nanotubes (CNT), via a facile method involving polymerization of melamine as the precursor in the presence of CNT in refluxing methanol. Under visible light, the CNT/mpg-C3N4 composite resulted in a greater than 8.6 × faster rhodamine B photodecomposition rate compared with bulk graphitic C3N4, and 1.6 × faster compared with pure mpg-C3N4. We attribute the promoted photocatalytic performance of the composite to the synergistic effects of open-ended CNT and mpg-C3N4. The highly interconnected CNT in mpg-C3N4 effectively enhances the transfer of photo-generated electrons, harvests more incident visible light, and provides specific channels for oxygen adsorption and photoreactions. We propose a possible reaction mechanism and report a scavenger experiment that found that superoxide radical (·O2−) is mainly responsible for dye photodegradation. The CNT/mpg-C3N4 retained good stability after several cycles. This work supplies a promising method of exploiting a stable, metal-free, efficient, and visible light-driven semiconductor to enhance solar energy use for environmental remediation.