Abstract: In this study, N-doped carbon quantum dots (NCQD_S)/TiO₂ composite photocatalytic material NCP was successfully prepared by a simple hydrothermal method. The morphology, crystal structure and functional groups of the prepared composite photocatalytic material were characterized by SEM, XRD and FTIR. Meanwhile, the effects of preparation conditions and degradation conditions on the degradation of methyl orange using the prepared composite photocatalytic material were investigated. The results showed that TiO₂ and NCP are mainly anatase type, accompanied by a small amount of rutile crystal structure. The NCQDS characteristic group has no obvious influence during the preparation process. The efficiency of methyl orange degradation could reach over 85.5% after 4 hours when the loading amount of NCQDS was 20%, the amount of NCP was 0.5g/L and the pH was 3. The acidic solutions were favorable for photocatalytic degradation of methyl orange. The degradation process of methyl orange by NCP accords with the first-order kinetic model of Langmuir-Hinshelwood (L-H), and the apparent rate constant decreases with the increase of initial concentration of methyl orange. The NCP has good stability and can be reused.

Key words: N-doped modification, TiO₂, composite catalyst photocatalysis