Construction of CNCs-TiO2 heterojunctions with enhanced photocatalytic activity for crystal violet removal

In this study, CNCs-TiO2 heterojunctions were synthesized successfully via a two-step method. The obtained materials were systematically characterized by a series of technologies including XRD, TEM, HRTEM, FT-IR, XPS, UV-DRS, PL and EIS. Moreover, the photocatalytic activity of CNCs-TiO2 was evaluated by the photodegradation of crystal violet (CV) under UV and visible light irradiation. The results of characterization demonstrated that the CNCs-TiO2 heterojunctions were formed. For composite CNCs-TiO2, the anatase TiO2 was uniformly dispersed on the surface of CNCs with graphite structures via a new chemical bond, Ti-O-C and the growth of crystalline grains was inhibited. The photo-absorbing range of TiO2 was extended to the visible light region after coupling with CNCs leading to the enhancement of light-harvesting ability. In addition, compared with pure TiO2 particles, the recombination of photoinduced electrons and holes was restrained. The photodegradation experiment indicated that the CNCs-TiO2 exhibited enhanced photocatalytic activity in contrast with TiO2 under UV and visible light irradiation, which was the result of the combined action of improved adsorption capability, enhanced light harvesting performance and efficient charge separation and transfer. The degradation of CV in the photocatalytic system followed the pseudo-first-order kinetics model. Lastly, the main mechanism for the enhanced photocatalytic activity of CNCs-TiO2 was significantly put forwarded.