Modify and Structure Control to Study the Photocatalytic Performance of g-C3N4

Author:Ma Yong Ning

Supervisor:fan jun

Database:Doctor

Degree Year:2018

Download:1327

Pages:164

Size:11020K

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With the high development of modern industry system,the energy shortage and environmental problems have transferred to the primary crisis of human beings,which are the two problems hard to solve.Moreover,the acid rains are also seriously in recent years with the aggravate of environmental problems.Besides,much dollars and human resource are consumed to release or suppress the corrosion of steel products each year all over the world.To solve above problems,photocatalytic technology,using the sunlight as energy,have been thinked as the most effective project to overcome the mentioned problems and resolve them in roots.Photocatalyst is the most restrict for the application of photocatalytic technology.The traditional photocatalyst Ti O2 was drawn much attention caused by the chape,nontox and good stability.However,the sharp absorption bond refrained the absorption property in visible light,which hard to use in practical application.To overcome the mentioned drawbacks,professor Wang reported the g-C3N4 had a good performance on H2 production under visible light irradiation.Unfortunately,the high recombination rate,big resistance value and small specific surface area of pristine g-C3N4 refrained the application of them.To overcome the drawbacks of pristine g-C3N4,the buck g-C3N4 was firstly exfoliated to g-C3N4 nanosheets with few layers or single layers structure to short the transport distance of charge carriers to improve the photocatalytic performance.Then coupling the other photocatalyst with lower conduction bond to refrain the recombination rate of charge carriers.In the last,controlling the position of Ag nanoparticles in heterojunctions to improve the photocatalytic performance.The details showed as below.(1)The buck g-C3N4 and WS2 were exfoliated to nanosheets with few layer structure or single layer structure,respectively.The exfoliated nanosheets samples were used to splitting water for H2 production under simulated sunlight irradiation and the H2 production rate was increased from 30.57 μmol h-1 and 3.80 μmol h-1(unexfoliated samples)to 35.32 μmol h-1 and 4.38 μmol h-1(exfoliated samples),respectively.The results indicated that the exfoliated nanosheets are benifite for the transportation of charge carriers from internal layers to surface layer to enhance the H2 production rate.After that,the Ag nanoparticles were deposited on the surface of g-C3N4 nanosheets and WS2 nanosheets to improve the H2 production rate,the calculated value was further enhanced to 53.69 μmol h-1 and 21.34 μmol h-1,which is 1.52 times and 2.36 time higher than that of pure nanosheets,respectively.The emhamced performance on H2 production may be caused by the Ag nanoparticles suppressed the recombination rate of charge carriers effectively.In the last,the WS2 nanosheets were composited with g-C3N4 nanosheets for the establishment of heterojunction,the H2 production rate of established heterojunction was enhanced from 30.57 μmol h-1(g-C3N4 nanosheets)to 45.81 μmol h-1(heterojunction),which can be owned to the established heterojunction can also suppress the recombination rate of charge carriers.(2)Through the position of intercalated Ag nanoparticles to control the structure of as-prepared heterojunction.The Ag nanoparticles were intercalated into the interlayer of g-C3N4 and WS2 nanosheets and deposited on the surface of heterojunction,respectively.The performance of as-prepared samples were used to splitting water for H2 production and NO degradation under simulated sunlight irradiation.The results indicated that the intercalated samples had a good performance on H2 production and NO degradation than that of deposited samples.Besides,the steability of as-prepared samples were evaluated by circulation experiments.The active species trapping experiments revealed that the excited electrons is the only active specie for H2 production.The enhanced mechanism for H2 production and NO degradation can be owned to the intercalated Ag nanoparticles can suppress the recombination rate of charge carriers,enhance the absorption property and absorbtion property of samples,which can improve the photocatalytic performance of samples.(3)In this section,the Fe2O3 particles were intercalated the interlayer of g-C3N4 and deposited on the surface of g-C3N4 nanosheets,respectively.The photocatalytic performance of as-prepared samples were evaluated by the degradation of Rh B under simulated sunlight irradiation.The results indicated that the Fe2O3 particles deposited samples had a good performance on degradation of Rh B and the final degradation rate was reached to about 95%.However,the degradation rate in five times circulated experiments were decreased rapidly and accelerate decrease,the reasons can be ascribed to the deposited Fe2O3 particles were dissociated from g-C3N4 nanosheets and the dissociated rate was accelerated with the prolong of irradiation time.Differently,the Fe2O3 particles intercalated samples had a poor performance on Rh B degradation compared with deposited samples,but the stability of them are much priority than that of deposited samples.(4)The valance state of intercalated Fe2O3 particles after photocatalytic performed samples were identified by XPS spectra,the results indicated that the Fe2O3 particles were reduced to Fe atoms by the excited electrons generated from g-C3N4.After that,the pristine g-C3N4 samples were coated on the surface of carbon steel plates to resistance the corrosion of the plate,the results revealed that the pristine g-C3N4 samples can suppress the corrosion of steel plates,which can be owned to the excited electrons reached to the surface of steel plates and consumed firstly.Thus,the freedom electrons in the steel plates were reserved and can’t be corroded.To improve the performance of pristine g-C3N4 samples on the performance of rusts resistance,the Ag nanoparticels were intercalated into the interlayer of g-C3N4 samples to resistance the corrosion of plate.The excited electrons can be transferred from internal layers to surface layers through the intercalated Ag nanoparticels and the excited electrons will be reached to the surface of steel plate with little energy consumption or without energy consumption.Therefore,the resistance performance of Ag nanoparticels intercalated samples was priority than that of pristine samples.