Controllable Fabrications And H₂-producing Performances Of Covalent Triazine Framework Based Photo Catalysts

Shortage of natural resources is one of the serious problems faced by the human beings.The semiconductor photocatalytic hydrogen evolution technology is thought to the efficient technology to resolve the drawbacks.With the development of the photocatalytic hydrogen evolution technology,hundreds of photocatalytic materials have been explored.Recently,covalent triazine frameworks(CTFs)composed of triazine units have attracted much attention for the unique chemical functionalities and structural properties.Our previous study shows that covalent triazine frameworks(CTF-T1)exhibits photocatalytic activity for H2 evolution under visiblelight irradiation.However,the drawbacks such as the narrow photo-response range,high recombination rate of photo-induced carriers and so on limited the enhancement of photocatalytic activity of CTF-T1.Therefore,to construct the covalent triazine framework based photocatalysts with wide photo-response range and low recombination of photogenerated carriers will have great significance for improving the photocatalytic hydrogen production activity.The thesis constructed several covalent triazine framework based photocatalysts with different methods.The physical-chemical structures,photoelectric properties and photocatalytic hydrogen production activities was characterized and tested in detail.The reasons for the improvement of photocatalytic hydrogen production for CTFs based photocatalysts were discussed.The main works include as follows:(1)the study of structures,photoelectric properties and photocatalytic hydrogen production activities on the Zn-doped CTFs photocatalyst,(2)the mechanism of enhancement of photocatalytic hydrogen production activities,the separation efficiency of photoinduced carrier and electronic band structures on Fe-doped CTFs photocatalyst,(3)The relation between morphologies,structures and photocatalytic hydrogen production activities on CTFs/rGO composite photocatalyst.The main results and conclusions obtained from this paper are presented as follows:(1)The zinc-doped CTFs(Znx/CTF-T1)have been successfully prepared by a low-temperature heat treatment method using CTF-T1 and zinc chloride(ZnC12)as precursors.The introduction of Zn adjusted the electronic band structure of CTF-T1,which led to an enhanced optical adsorption of visible light and thus a 5 times higher photocatalytic activity was obtained.(2)The iron-doped CTFs(Fex/CTF-T1)have been successfully prepared by low-temperature heat treatment method using CTF-T1 and ferric chloride as precursors.The results indicate that an appropriate Fe content could significantly adjust the band structure of CTF-T1.The Fex/CTF-T1 photocatalysts exhibited an improved production and separation efficiency of photoinduced carriers and showed much higher photocatalytic hydrogen evolution activity than the pristine CTF-T1.The highest photocatalytic activity obtained at Fe10/CTF-T1 was about 28 times higher than that of the pristine CTF-T1.(3)The CTF-T1/rGO composite photocatalyst have been successfully obtained by a photoreduction method using CTF-T1 and graphene oxide(GO)as precursors.Characterization results show that the loading of an appropriate rGO can not only enhance the light utilization efficiency but also improve the production and separation efficiency of photoinduced electron-hole pairs and finally enhance the photocatalytic hydrogen evolution activity effectively of the CTF-T1.The CTF-T1/rGO-2 sample exhibited the best photocatalytic activity toward photocatalytic hydrogen evolution.The rate of hydrogen evolution reaches 17.88 ?mol h-1.The thesis mainly discusses the relation between different construction methods and reaction mechanism aiming to improve the photocatalytic hydrogen production performance of the CTFs which will provide theoretical and experimental evidence for the development of the covalent triazine framework based photocatalysts.