Preparation Of Graphene Quantum Dot Composite Metal Oxide And Their Photocatalytic Properties

At present,clean energy has attracted much attention due to its environmental protection.Among them,due to the abundant reserves,high calorific value and no pollution,hydrogen energy has a great potential development value.Photocatalysis,as one of the important means of preparing hydrogen,limits its wide application due to the low efficiency of most photocatalysts.Therefore,the preparation of a highly efficient photocatalyst is one of the core steps to improve photocatalytic performance.In this paper,the size of graphene quantum dots(GQDs)was controlled and combined with titanium dioxide(TiO2)string sphere structure to study the photocatalytic hydrogen production performance of the composites.It is found that the composite structure effectively improves the efficiency of hydrogen production by TiO2-The main research contents of this paper are as follows.(1)The size of GQDs is regulated by a top-down approach.By adjusting the oil bath temperature,GQDs with diameters of 5 nm and 10 nm,were prepared.Blue and yellow fluorescence were emitted under ultraviolet light of 365 nm,respectively.The visible light absorption range of 5 nm GQDs can be around 450 nm.while the absorption range of 10 nm GQDs is red-shifted to about 500 nm.Two kinds of GQDs were used as photocatalysts to decompose water to produce hydrogen in the whole spectrum.It was found that the 5 nm GQDs had better photocatalytic performance due to the short distance of electron transport.(2)Titanium dioxide(TiO2)string sphere structure with a length of 10?m and a radius of 0.72?m was prepared by hydrothermal method and combined with different size GQDs by ultrasonic stirring.It has been found that after the TiO2 string sphere combined with GQDs,the epoxy functional group rearrangement in GQDs achieves C-O-Ti bonding.The interface electron transport of GQDs/TiO2 is enhanced.In the composite structure.GQDs can act as electron donors.The photoexcited electrons excited on the surface of GQDs can be transferred to the surface of TiO2,which effectively reduces the recombination of electron-hole pairs.Moreover,GQDs can be used as photosensitizers to extend the visible light response region of composite structures,which affects the performance of photocatalytic hydrogen production.The composite was applied to the photocatalytic hydrolysis hydrogen production process to analyze its photocatalytic hydrogen production performance.Results analysis showed GQDs/TiO2(10nm)due to the long electron transport distance,the hydrogen production rate is 13.3?molh-1.While GQDs/TiO2(5nm)has the highest photocatalytic hydrogen production rate under the whole spectrum,which can be increased to 18.3?molh-1,about three times higher than the TiO2 string sphere alone.