The Preparation Of Carbon Quantum Dots And Their Catalytic Properties For Aerobic Oxidation Of Alcohols

In this paper, high quality CQDs were synthesized via a simple one-pot electrochemistry method using cheap graphite rod as substrate materials, without the assistance of any chemicals but only pure water. This high productivity method makes the synthetic process of CQDs synthesis both economical as well as environment-friendly. We have developed a simple yet effective ultrasonic method for generating N-CQDs, which show unique property from CQDs. The morphologies and composition of the resulting CQDs catalyst and N-CQDs were characterized by Transmission electron microscopy(TEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR), Raman spectra(Raman) and so on. The obtained CQDs was determined to be sp2 hybrid structure, with uniform particle size distribution and the average particle size was about 4 nm. In the electrochemical oxidation process more surface functional groups were introduced.Transition metal-free oxidation of alcohols catalyzed by CQDs with NaClO oxidant using water as an only solvent was developed. As a result, 100 mg CQDs, 10 mL of NaClO(10 %) and 70 ℃were chosen as a suitable reaction condition for oxidation of alcohols. The conversion of 75 % from benzyl alcohol to benzaldehyde could be achieved within 6 h without the formation of byproducts such as benzoic acid. At the same time, in absence of catalyst, the system can only deliver a very low conversion, demonstrating that the CQDs are the active catalyst. Compared with other carbon nano catalyst, such as carbon nanotubes and graphene. CQDs exhibited high activity. Meanwhile, CQDs catalyst also displayed high activity and stability in the oxidation of other alcohols. With respect to the pure carbon quantum dots, the catalytic performance nitrogen-doped carbon quantum dots has improved. Its high activity mainly due to its smaller particle size and more oxygen-containing surface functional groups.Considering the optical properties of carbon quantum dots, we try to improve the catalytic activity of the CQDs by introducing photocatalysis. After irradiation under visible light resources, it was found that the catalytic performance of the CQDs catalyst has been improved, confirming the idea. The proposed mechanism for the efficient selective oxidation of alcohols catalyzed by CQDs catalyst under visible light was given out.In summary, CQDs catalyst were successfully prepared by an electrochemical method. The CQDs catalyst showed high catalytic activities and selectivity for selective oxidation of alcohols. Its small particle size and large amounts of surface oxygen containing groups contributes to their high catalytic performance.