The photocatalytic activity and purification performance of g-CN/carbon nanotubes composite photocatalyst in underwater environment.

Graphite carbon nitride (g-CN) is a promising photocatalyst for its high catalytic activity, low-cost and high-biosafety characteristics. Due to the complexity of underwater photochemical reaction conditions and the disadvantages of g-CN itself such as low specific surface area, easy recombination of photogenerated electron-hole pairs and insufficient light absorption capacity, the application of g-CN in the field of water purification is limited. For improving underwater photocatalytic performance of g-CN, a g-CN/carbon nanotubes (CNT-CN) composite photocatalyst with high specific surface area and enhanced light absorption capacity were prepared by in situ solvothermal method. Its photodegradation efficiency at different underwater transmission light was further studied. The results show that CNT has good compatibility with g-CN. g-CN can grow in situ on the surface of CNT and form a stable composite structure. Moreover, its degradation efficiency under long-wavelength irradiation is improved significantly. The degradation rate of CNT-CN at 550-700 nm was about 3 times than that of g-CN. Furthermore, CNT-CN can maintain higher photocatalytic activity under water. At 40 cm depth where light intensity and ultraviolet spectra were attenuated 63.8% and 80.1%, respectively, the degradation rate of CNT-CN3 can still reach 3.49 times than that of g-CN. Based on this study, the introduction of CNT effectively promotes the electron-hole separation efficiency of g-CN, widens its spectral response range, and thus improves its underwater degradation efficiency.