One-pot synthesis of high performance CQDs/TiO2 nanocomposites without carbon source addition

In this work, oxygen vacancies containing CQDs/TiO2 nanocomposites with ultra-low bandgap (2.32 eV) and visible-light response were fabricated by one-pot method without carbon source addition under nitrogen atmosphere for the first time. Mechanism analysis revealed that the carbon atoms in tetrabutyl titanate and glacial acetic acid were the carbon source of the CQDs, and the oxygen vacancies were formed by oxygen-free atmosphere. The CQDs and oxygen vacancies enhanced the separation efficiency of the photoinduced electron-hole pairs and visible-light absorption, and eventually improved the visible-light photocatalytic activity. Under UV and visible-light illumination for 140 min, the photocatalytic degradation rate of Rhodamine B reached 97.82 % and 97.99 %, respectively. The photocatalytic reaction rates were much higher than that of the pure TiO2. Comparative experiments demonstrated that the tetrabutyl titanate was the major carbon source of the CQDs, while the glacial acetic acid was the minor. This strategy provided a facile approach to prepare CQDs/TiO2 nanocomposites without carbon source addition. Moreover, the nanocomposites also exhibited excellent visiblelight photocatalytic properties for degradation of tetracycline and Cr(VI). Under visible-light irradiation for 140 min, the degradation rates of tetracycline and Cr(VI) were 91.92 % and 70.63 %, respectively. Compared with recent studies, this work had great potential in environmental remediations and commercial applications.