Solvothermal synthesis of g-C3N4 nanosheets modified carbon quantum dots for enhanced photocatalytic degradation

The incorrect disposal of industrial waste water has caused widespread concern of researchers due to its serious harm to people's health and ecological environment. Photocatalytic technology is widely used for wastewater purification owing to its simple operation, no secondary pollution and clean energy. In this study, carbonaceous composites were constructed by combining graphite-phase carbon nitride (g-C3N4) nanosheets with carbon quantum dots (CQDs) via hydrothermal method. The size of CQDs was about 8 nm, distributing over the surface of g-C3N4 nanosheets, and the existence of their interface interaction was confirmed. The photocatalytic degradation of methyl orange (MO) is considered to appraise the photocatalytic performance of the g-C3N4/CQDs composites under visible light. The obtained composites display better photocatalytic activity than the pure g-C3N4 nanosheets. The obtained g-C3N4/CQDs composite (CN-20) from 20 mL of the CQDs solution (∼1 mg mL−1) and 20 mg of g-C3N4 nanosheets displays the excellent photo-degradation efficiency and its apparent rate constant (kapp) is 4.0 times that of g-C3N4 nanosheets. In addition, CN-20 exhibits almost negligible influences of real environmental (pH value, inorganic anions, humic acid and source of water) on the degradation of MO, indicating potential in practical application. Furthermore, the g-C3N4/CQDs composite shows the enhanced cycle stability and the postulated mechanism of MO photocatalytic degradation is illustrated in detail.