Preparation of carbon quantum dots/TiO2 composite and application for enhanced photodegradation of rhodamine B

Titanium dioxide-coated carbon quantum dots (CQDs/TiO2)-based composite was prepared by sol-gel hydrolysis and studied as a catalyst for photodegradation of rhodamine B (RhB) in aqueous solution. The photocatalytic activity and stability of the composite was investigated under visible light. The structure, optical and electrochemical properties of as-prepared samples were characterized by means of SEM, TEM, XRD, XPS, FT-IR, BET, PL, UV-vis/DRS and EIS analyses. The results show that the absorption intensity of the CQDs/TiO2 composite is increased compared to that of TiO2. In addition, the absorption wavelength of the composite material is redshifted to the visible region. When the content of CQDs in composite is 5 % (based on the mass of TiO2), the obtained CQDs/TiO2 exhibits excellent catalytic activity for the degradation of RhB. The degradation rate of CQDs/TiO2 is 85.47 %, which is 5.5 times higher than that of the pure TiO2. The catalytic degradation rate of RhB remained above 80 % even after 4 cycles. The photocatalytic mechanism of RhB by CQDs/TiO2 reveal holes (h+), superoxide anion radical (.O-2(-)), hydrogen peroxide (H2O2), and hydroxyl radical (.OH) are the main active species in the photocatalytic process. The oxidizing abilities of the four substances are in the order of .O-2(-) > h(+) >.OH > H2O2. This work highlights the enhanced photocatalytic performance of CQDs/TiO2 composite for the treatment of organic pollutants.

Automated summary

In this study, a titanium dioxide-coated carbon quantum dots (CQDs/TiO2) composite was prepared and studied as a catalyst for the photodegradation of rhodamine B (RhB) in water. The composite showed enhanced photocatalytic activity and stability under visible light. The mechanism of the photocatalytic process was found to involve various active species, including holes (h+), superoxide anion radical (.O-2(-)), hydrogen peroxide (H2O2), and hydroxyl radical (.OH). This work highlights the potential of CQDs/TiO2 composite for the treatment of organic pollutants.