| Among various renewable energy projects,semiconductor photocatalysis can be used as a viable technology to obtain inexhaustible clean solar energy.Because of its great potential in energy and environmental applications,it has gained considerable interdisciplinary attention.To date,the direct conversion of solar energy to energy fuels and chemical energy has been recognized as one of the green sustainable ways to address future energy and environmental crises.As a compelling conjugated polymer,g-C3N4 has a unique electronic band structure,high physicochemical stability and "rich earth".Since g-C3N4 has a suitable electronic band structure(?2.7 eV),it has the advantages of no toxicity,low cost,good stability and the like.The use of metal-free and visible-light-responsive photocatalysts in the field of solar energy conversion and environmental remediation has attracted widespread attention in the academic community.In order to further improve the catalytic performance of g-C3N4-based photocatalysts,this paper started to reduce the recombination rate of photogenerated electron-hole pairs and expand its photoresponse range,and constructed g-C3N4-based Z-Scheme photocatalyst and lighted it.Catalytic hydrogen production performance was studied.This thesis focuses on the regulation mechanism of the band photo-regulation,interface electron transport and surface plasmon resonance of Ag on the photoelectric and photocatalytic properties of the catalyst.The main research contents of this thesis are as follows:In the first chapter,we mainly introduce the basic principle,development history and current problems of Z-Scheme photocatalytic system,and summarize the structure,optical properties,doping modification of g-C3N4 and the construction of g-C3N4 based composite photocatalyst.The research status is presented,and the topic selection and main research contents of this thesis are expounded.In the second chapter,we mainly use the band structure of g-C3N4 to adjust this feature,doping modification of g-C3N4,and control the P-doped PCN conduction band(CB)to move in a more negative direction.The valence band(VB)of Ag-doped ACN moves in the direction of correction,and the positional regulation of ACN and PCN band positions is achieved.The PCN/ACN homogenous direct Z-Scheme photocatalyst is successfully constructed,and different composite ratios for photocatalysis are discussed.The effect of hydrogen production performance significantly increases the photocatalytic cracking of hydrogen produced by water.Compared with the monomer,the performance of the Z reaction is much higher than that of the monomer,and the light absorption is also enhanced.It can be seen from the photocurrent and the impedance that the heterojunction has higher photo-generated charge separation and migration efficiency.This work provides a valuable reference for the construction of high-efficiency Z-Scheme photocatalysts based on band structure control.In the third chapter,we successfully prepared PCN/Ag/BVO all-solid Z-Scheme photocatalyst by simple physical compounding,and applied it to the photocatalytic cracking of hydrogen production.The results of XRD,SEM and TEM showed that the exposed(010)surface flaky bismuth vanadate with large specific surface area was successfully prepared,and the success of PCN was combined with(010)surface bismuth vanadate.In this work,we use the energy band structure of g-C3N4 to adjust this characteristic,and make it have better energy level matching with BVO through doping control;improve the inter-interface electrons by regulating the optimal loading of Ag.Synergistic effects of transmission and surface plasmon resonance.Based on the above factors,the PCN/Ag/BVO all-solid Z-Scheme photocatalyst has excellent visible light catalytic hydrogen production performance,and the test condition is 4.5 times higher than that of the monomer.The fourth chapter summarizes the paper and looks forward to the work to be carried out. |
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