Preparation And Photocatalytic Properties Of Graphene Based Photocatalytic Composites

With the development of industrialization in modern society,water pollution has become a serious problem.Photocatalysis technology is considered to be one of the most effective technologies to solve water pollution.This study,the photocatalytic efficiency of some semiconductors was improved by doping graphene substrate..In the experiment,two materials of graphite carbon nitride(g-C3N4)and zinc oxide(ZnO)were selected as the research objects.Related content:(1)Study the adsorption performance of graphite oxide.Study of adsorption kinetics and adsorption isotherm model,it was found that the adsorption process of graphite oxide to RhB conforms to the pseudo-second-order kinetic model and Langmuir isotherm model.The results show that the maximum theoretical adsorption capacity of graphite oxide for RhB can reach 578.0 mg g-1.Meanwhile,it was found that pH had a great influence on the adsorption capacity of graphite oxide.Within a certain range,the adsorption capacity of graphite oxide increases first and then decreases with the increase of pH value.When the pH is in the range of 5-6,the adsorption of graphite oxide to RhB is the best.(2)Graphite carbon nitride(g-C3N4)was selected as the substrate for catalytic research.At the same time,MoS2 was selected as the auxiliary catalyst for g-C3N4.The composite catalyst p(g-C3N4/5MoS2)was obtained by mechanical compounding and protonizing.Experimental data show that the degradation rate of MO dyes by the protonated p(g-C3N4/5MoS2)composite catalyst is increased by 60%compared with pure g-C3N4.Meanwhile,the kinetic constant of p(g-C3N4/5MoS2)is 0.02395 min-1,which is 6.4 times that of pure g-C3N4.Through UV-vis and other tests,it was found that a z-type heterojunction can be formed between g-C3N4 and MoS2,reducing the recombination rate of electrons and holes in the composite.These results indicate that the p(g-C3N4/5MoS2)composite catalyst can be used as the cornerstone for the further synthesis of efficient ternary composite catalysts.(3)GO was added to the p(g-C3N4/5MoS2)composite catalyst to improve its photocatalytic efficiency by physical mechanical method.The photocatalytic test of the ternary composite catalyst p(g-C3N4/5MoS2)/GO found that when the ratio of GO was 1.5 wt%,the p(g-C3N4/5MoS2)/1.5GO composite was better and the catalytic degradation effect on MO was better than that of p(g-C3N4/5MoS2).By comparing the kinetic constants of the catalysts,it can be found that the kinetic constant k of p(g-C3N4/5MoS2)/1.5GO is 0.03105 min-1,which is about 1.3 times that of p(g-C3N4/5MoS2)and 8.4 times that of the pure g-C3N4.It was found that the photocatalytic enhancement mechanism of o(g-C3N4/5MoS2)/1.5GO composite catalyst was mainly related to GO.The conductivity of GO can accelerate the separation rate of electrons and holes in g-C3N4 and MoS2,thus increasing the photocatalytic activity.At the same time,take advantage of both the specific surface area and the adsorption capacity of GO.(4)Zinc oxide(ZnO)was selected as photocatalytic substrate.The ZnO/CdS/GO composite catalyst was prepared by a hydrothermal synthesis method.The photocatalysis results show that the binary composite catalyst ZnO/2CdS has the best degradation effect on RhB of 84%,which is 20%higher than pure ZnO,and the degradation kinetic constant is 1.5 times.With GO added on the basis of ZnO/2CdS,the degradation efficiency of the ternary composite catalyst ZnO/2CdS/10GO is up to 95%,which is about 50%more than that of pure ZnO.The kinetic constant of ZnO/2CdS/10GO increased to 0.0945 min-1,which was 4.8 times that of pure ZnO.The results of the photocatalytic mechanism study show that the photocatalytic activity enhancement of ternary composite catalyst is mainly due to the following:First,the introduction of GO can transfer the photogenerated electrons in the conduction band of CdS and ZnO to the surface of GO,reducing the recombination rate of photogenerated electron-hole pairs in CdS and ZnO,improving the photocatalytic efficiency and reducing the photocorrosion phenomenon of CdS,enhancing the stability of the catalyst.The photodegradation of RhB was carried out by the photoconductive holes on the catalyst conduction band and the reduction of photogenerated electrons on the surface of GO;Second,due to the heterojunction between CdS and ZnO,the electrons in the CdS conduction band can be transferred to the ZnO conduction band,and the holes in the ZnO valence band can be transferred to the CdS valence band,which improves the photocatalytic activity of the catalyst.At the same time,the introduction of GO improves the adsorption efficiency of the composite catalyst to RhB,increases the contact frequency of the catalyst and pollutants,and accelerates the photocatalytic degradation rate of the ZnO/2CdS/10GO.Figure[44]table[11]reference[134]...