Preparation And Photocatalytic Properties Research Of Graphene Quantum Dots/graphtic Carbon Nitride

Graphene quantum dots?GQDs?are quasi zero dimensional graphene materials,which are less than 100 nm in three dimensions.Because of its adjustable energy band,upconversion luminescence and electron transfer,it has been widely applied in the field of photocatalysis.In addition,the rich oxygen functional groups on the surface of GQDs have good dispersion and are easily combined with other inorganic particles.As a metal free photocatalyst,carbon nitride?g-C₃N₄?has attracted wide attention from researchers.Under the irradiation of simulated sunlight,g-C₃N₄ has good photocatalytic activity for organic pollutants.However,as a photocatalyst,g-C₃N₄ has low specific surface area,high electron and vacancy binding rate,and seriously affects the utilization of g-C₃N₄ to sunlight.At present,there are many ways to improve the photocatalytic efficiency of g-C₃N₄,such as doping of semiconductor and doping of metal ions.However,these methods can not solve the problem of high electron and vacancy binding rate.In this paper,GQDs and g-C₃N₄ are combined to transfer electrons and upconversion luminescence through GQDs,which greatly reduces the binding rate of electrons and vacancies.The main contents and results are as follows:In this paper,GQDs was prepared by hydrothermal method using citric acid as carbon source.The mixture of GQDs aqueous solution and urea and melamine was dried at80?.The mixture was dried in a muffle furnace and sintered to obtain GQDs/g-C₃N₄complex.The surface morphology,structure and composition of the samples were analyzed by transmission electron microscopy?TEM?,X ray diffraction?XRD?,X ray photoelectron spectroscopy?XPS?,Fourier infrared spectroscopy?FT-IR?,fluorescence spectroscopy?PL?,scanning electron microscope?SEM?and so on.Under the irradiation of the simulated sunlight,the organic pollutants were degraded by the samples.The results showed that the difference of GQDs doping content would affect the photocatalytic degradation activity of organic pollutants.In order to further reduce the binding rate of electrons and vacancies,oxalic acid?OA?was added to the g-C₃N₄/GQDs photocatalytic process.Through systematic research,it is concluded that OA can improve the photocatalytic efficiency by controlling the transfer of vacancies.It is found that OA does not decompose during the photocatalytic process and does not produce harmful substances.Therefore,the photocatalyst system prepared in this paper has high catalytic efficiency and good stability.