Structure Engineering and Photocatalytic Structure-Activity Relationship Base on One Dimensional Cd-Zn-S Solid Solution

Author:Han Zhong Hui

Supervisor:chen gang

Database:Doctor

Degree Year:2019

Download:80

Pages:138

Size:9244K

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Semiconductor solar photocatalytic technology is a new energy production method that converts solar energy directly into chemical energy for utilization.It is one of the most promising technologies to solve the energy and environmental crisis of human society in the 21st century.However,due to the low performance,instability and other factors of semiconductor photocatalysts,the practical industrial application is still unachievable.In this context,the development of semiconductor photocatalyst with high performance and stability becomes the key to solve this problem.Cd-Zn-S solid solution photocatalyst is a kind of semiconductor photocatalyst with high research value and wide application prospects.In this thesis,Cd-Zn-S solid solution photocatalysts were prepared with basic one-dimensional microstructure through morphology control.It was modified and optimized based on its specific one-dimensional structure.Effects of its atomic structure,electronic structure,carrier transport behavior,physical optics and photoelectrochemical properties on the photocatalytic water splitting hydrogen evolution performance were further studied.Growth pattern of crystal morphology was studied as well.One-dimensional Cd-Zn-S solid solution nanowires with large aspect ratio were prepared.First of all,the addition of TGA molecule enables the derived metal organic complexes to provide a similar chemical environment for the heterogeneous metal ions and effectively homogenize the heterogeneous metal ions in the initial reaction system.Secondly,the bi-hydrogen bonding between TGA-Cd2+/Zn2+complexes plays a guiding role in the crystal growth process of one-dimensional nanowires.This uniform one-dimensional nanowire morphology leads to stronger light absorption,provides more active sites for photocatalytic reaction,shortens the transmission path of photogenerated carriers,and reduces the transmission resistance of photogenerated carriers,and thus promots the photocatalytic water splitting hydrogen evolution activity.Cd-Zn-S solid solution with 3D-star topological structure was prepared by polypeptide-like metal-organic complex crosslinking reaction.A 3D topological structure was constructed by multiple cross-linking of polypeptide-like molecules produced by condensation of amino acid metal-organic complexes.This 3D star topology Cd-Zn-S solid solution has a very large specific surface area(149.36m2·g-1).The increase of specific surface area effectively improves the light absorption performance of the sample and the utilization rate of solar energy.The photocatalyst also shows obvious quantum effect,which greatly improves the redox ability of photogenerated carriers.These two synergistic effects effectively improve the photocatalytic water splitting hydrogen evolution activity.PANI@Cd-Zn-S composite photocatalyst with core-shell structure was successfully prepared by a two-step method.It was found that the newly formed-Cd···N-bonds at the PANI/Cd-Zn-S interface could serve as the electron transport channel across the interface,which achieve the selective interfacial transport of photogenerated charge carriers(electrons and holes),and promote the spatial separation of photogenerated carriers.Meanwhile,in the composite structure,t he electron delocalization effect in Cd-Zn-S is enhanced,which improves the photocatalyst conductivity.The photocatalyst material has been effectively improved in light absorption intensity and solar energy utilization range.The activity of solar photocatalytic hydrogen production has been increased by nearly 5times(744.8μmol·h-1),and the activity can remain basically stable after 12 h of continuous photocatalytic reaction.The photocatalyst of Cd-Zn-S nanorods with self-rectified structure was prepared successfully.Under the effects of the built-in potential field provided by nearly ordered arrangement of fault induced self-rectifier,it promotes the spatial separation of photogenic carriers.The oxidation of lattice S atoms by photogenic holes was effectively inhibited.The prepared self-rectified Cd-Zn-S nanorods photocatalyst can react continuously for more than 72 h under visible light irradiation,and basically keep the hydrogen production rate stable.