Study on the structure and photocatalytic performance of MWCNT/TiO ₂ synthesized by supercritical hydrothermal method

Abstract In this study, multi-walled carbon nanotubes and TiO 2 composite materials (MWCNT/TiO 2 ) were respectively synthesized using supercritical hydrothermal synthesis combined with a secondary hydrothermal doping method and an in-situ doping method via a one-step hydrothermal process. The effects of different preparation methods and doping concentrations on the crystalline structure, particle size, and photocatalytic performance of TiO 2 were investigated. It was found that TiO 2 prepared through supercritical hydrothermal synthesis exhibited higher crystallinity and smaller particle size. After doping with hydroxylated MWCNT, the composite material demonstrated excellent photocatalytic performance for the degradation of methylene blue. The optimal photocatalytic activity was achieved at a doping concentration of 4 wt%, with a degradation rate reaching 69.8%. The enhanced performance is attributed to the formation of Ti2013C and Ti–O–C bonds between MWCNT and TiO 2 , promoting charge transfer, suppressing electron-hole recombination, and broadening the material’s optical absorption range. Further studies revealed that the composite material prepared by the one-step hydrothermal method exhibited lower crystallinity and weaker photocatalytic activity, with TiO 2 particles tending to coat the surface of MWCNT, thereby limiting its photocatalytic effectiveness. These findings provide significant theoretical guidance for developing highly efficient photocatalytic materials.