Preparation And Modification Of Carbon Quantum Dots And Nanoparticles,and Their Application In Photocatalytic Hydrogen Evolution

Along with the increasingly serious environmental pollution and dwindling oil resources,the preparation of semiconductor photocatalytic water electrolysis hydrogen has become a green solution to alleviate environmental pollution and resource shortage.Compared with oil resources produce hydrogen in common,this method has the advantages of renewable bioenergy;compared with hydrogen production from biomaterial,this method has the advantages of without long time the production of raw materials.In recent years,the semiconductor material substitute by carbon based materials as used in traditional photocatalytic electrolysis of water come into the scientist's vision.Compared with the traditional semiconductor photocatalyst,carbon based materias have a wide range of sources,non-toxic,can be extracted from the waste of natural materials which has been widely concerned.In many of the carbon based materials,nanomaterials show better photocatalyst,due to the large specific surface area and exhibit better photocatalytic effect.Based on natural waste as raw materials,these paper focus on the preparation of a variety of carbon based micro-nano materials and it's composite materials,these materials can be used for success preparation of the photocatalytic hydrogen production.In addition,this paper discusses the preparation methods?morphology?physical effects and chemical modification on the photocatalytic performance.The electronic distribution and charge density of nitrogen doped carbon based micro-nano materials were effectively adjusted to improve its catalytic performance.In this paper,the use of waste shrimp shell,using hydrothermal method in the absence of additional nitrogen containing raw materials synthesis nitrogen doped carbon quantum dots,under the condition of reaction 10 hours at the temperature of 200 degree centigrade.The average diameter of nitrogen doped carbon quantum dots is 3.5nm,the lattice spacing is 0.31nm,corresponds exactly to the 002 crystal structure of graphite,the structure of nitrogen doped graphite like carbon quantum dots.The surface of the materials contain a large number of oxygen and nitrogen groups,these groups are amino,carboxyl and hydroxyl groups.The fluorescent material shows the spectral peak position within 300⁴40nm with the increase of the excitation wavelength blue shift.The results show:from 1000nm to 200nm,the material has obvious absorption wavelength shift,with reduced ability to significantly enhance the light absorption material.Nitrogen doped carbon quantum dots in the presence of different concentrations of formic acid,show photocatalytic hydrogen production efficiency in different excited xenon light source.When the acid volume is less than 2ml.Hydrogen produced increases with the increase of addition of formic acid;when the volume is greater than 2ml,the volume of hydrogen increases no longer.Vapor deposition of inorganic chemical industry is one of the mature application processes.This paper has put driedcorncob with argon atmosphere protection in high temperature quartz tube calcination furnace;the reaction condition is 1000 degree centigrade for 4 hours.In the process of calcination,one part of the rubber pipe connects the end of quartz tube furnace;another part of the rubber tube was put into a receiver.The receiver is filled with ultrapure water which is used for receiving gas with carbon gas fluorescent microspheres from a tube furnace.?In argon gas flow rate of the reaction process is 150 ml/min.?Dialysis solution carbon fluorescent microspheres produced under certain time which can be used for different applications.The size distribution of carbon nanoparticles obtained is uniform,basically is about50nm.The diffraction peaks in XRD patterns in 23 degree obviously broadened,structure is a structured graphite carbon and disorderly intertwined.The surface of the carbon microsphere contains a large number of oxygen and nitrogen groups,these groups are amino,carboxyl and hydroxyl groups.The material is through continuous synthesis process,without acidification can emit strong light.In the presence of acid,the carbon microsphere showed photocatalytic activity under the xenon lamp.This paper adopts technology of quartz tube furnace calcinationathigh temperature for corncobcarbonized.The biomass carbon is composed of cellulose,hemicellulose and lignin which produced through poly-condensation reaction at high temperature.Compared to the traditional natural materials,such as graphite or carbon materials:it's has the featureof environmental protection,the superiority of the solution isbetter sustainability solution compared to mineral materials not.In order to obtain carbon nanoparticles with photocatalytic performance,this paper uses strong oxidizing acid on the surface of biomass carbon,the biomass carbon turns to loose and gets oxidation treatment.The acidification result that the surface of the material contains oxygen containing functional groups.This step for subsequent ultrasonic cutting materials,improves the luminescent properties and the water dispersion properties to prepare.Subsequently,sodium bicarbonate is used for treatment of biomass carbon on the material surface to neutralization,then the material is been used for dialysis experiments.Finally the biomass carbon was broken under ultrasonic dialysis,and then microporous membrane aperture of the filters been used,the yellow solution contains carbon nano-particle.This solution can be stored for a long time to be used at room temperature in this paper.At the same time,using the bio nitrogen doped carbon quantum dots and boron nitrogen co-doped carbon quantum dots were synthesized.These two kinds of quantum dots can be used in the absence of methanol as catalyst,repeated been used for photocatalytic hydrogen preparation.In this paper,using solvothermal method,puttingglucose in acetonitrile solvent for production of nitrogen doped carbon quantum dots?NCDs?,the synthesis method is simple and easy to operate,NCDs particles were prepared with uniform distribution,can be stably dispersed in aqueous solution.NCDs with uniform size distribution,the particle size was about 4 nm.400nm excitation light can excite the strongest the fluorescence emission peak.Compared with water as solvent,the particles is not easy to grow up and can show uniform sizeon the condition of acetonitrile as the solvent.Subsequently,the NCDs/TiO₂ composite materials were prepared using physical mixing and aging system.Because NCDs can also absorb ultraviolet light and visible light,effectively broadening the range of light absorption of TiO₂ material;at the same time,effectively prevent the composite of electrons and holes,greatly improve the photocatalytic efficiency.When the feed ratio is m?NCDs?:m?TiO₂?=15:85,the best catalytic effect shows.The using of materials not only have no toxicity and easily available raw materials,can effectively improve the photocatalytic performance.In this paper,methanol is used as solvent for hydrothermal method,hydrothermal reactor with graphite oxide solution for hydrothermal reaction in high temperature oven.The reaction conditions of 200 degree centigrade for 10h.Graphite oxide was cut into fragments of various sizes in the intense cutting force.Graphene quantum dot size is between 1.5nm⁴nm.Graphene quantum dot show good size distribution,no obvious agglomeration.The methoxy group into the surface of graphene quantum dot in chemical structure has more stable characteristics than hydroxyl or other functional group.In addition to the introduction of new functional groups,the most feature of this method is the only complete separation of carbon quantum dots with large size carbon particles through the simple static method.The main reason is to the decline in the proportion of hydroxyl groups in the reactants,for only a few products which is very small and dispersed in water.In addition,methanol itself can be prepared by biomass materials,and the price is lower than other several organic solvents.Therefore,this method is a low cost of the preparation of graphene quantum dot method.