Design And Synthetise Of Various Metal Sulfur Utilied In Photolysis Of Water

With the shortage of energy sources and increasingly deteriorating environmentalproblems，there is an urgent requirement for humans to search for a new andenvironment-friendly energy source. Hydrogen energy has been regarded as the mostpromising clean energy resources in the21st century, Among the various methods ofhydrogen production, how to utilize solar energy and efficiently produce hydrogen is thekey research object specially for researchers. Heterojunctionphotocatalystshave certaincharacteristics that special energy band structure and carrier transport, which caneffectively resist the combination between photogenerated electrons and holes toenhance the quantum efficiency, therefore, heterostructure has been extensively studiedin the field of photocatalysis.For these reasons, this dissertation would explore problems aboutheterojunctionnanomaterials as photocatalyst efficiently generate hydrogen from water,the main research works are as following:(1) Series of chalcopyrite compounds and its heterojunctions were synthesized byvacuum high temperature solid-phase method, such as CuInS2,AgInS2,NaInS2,LiInS2,KInS2,ZnGa2S4(defective chalcopyrite structure), and their heterojunctionCuInS2-In2O3, AgInS2-In2O3, AgGaS2-Ga2O3. Their photocatalytic water splittingactivity were deeply studied, and relevant mechanisms of photocatalytic hydrogenevolution were discussed in theory. We found that the most of sulfideswith chalcopyritestructure have lower bandwidth, their hydrolysis reaction could be carried out in visiblelight conditions, butits activity was lowly, although explored its several heterojunctions,its photocatalytic activity still did not be significantly improved, it’s necessary for nextresearch to utilize another design method to prepare heterojunctions possessed betteractivitybut AgGaS2-Ga2O3.(2) Focused on the research of ZnGa2S4and its related heterojunction.A series ofheterojunctions were synthesized byvacuum high temperature solid-phase method, suchas ZnS-ZnGa2S4, ZnS-Ga2S3-ZnGa2S4, ZnS-Ga2O3-ZnGa2S4, ZnS+Ga2O3. Theirphotocatalytic water splitting activity werestudied, simultaneously, its relevantmechanisms were discussed use certain theoretical knowledge. Through the study, wefound that the mesoporous micro-sheet ZnGa2S4possessed UV-visible lightphotocatalytic activity for water splitting, and belonged to the sulfides with defect chalcopyrite structure, it’s photocatalytic activity has reached about10times of thereference reagent CdS activity, Explored it’s severalheterojunctions, discoveredthat theoriginal ZnGa2S4with no more than ultraviolet activitycould possess visible lightphotocatalytic activity after modification,such as ZnS-ZnGa2S4, ZnS+Ga2O3could showwell photocatalytic activity for water splitting under visible light. Moreover, asemiconductor with sole ultraviolet response transform to visible lightresponsesemiconductorby doping modification, which also relate to the research ofZnGa2(1-x)In2xS4sosoloid of ZnGa2S4, then improve the utilization rate of visible light.(3) Studied the alum structure compounds: NaGa3(SO4)2(OH)6andH3OGa3(SO4)2(OH)6, they were synthesized by hydrothermal method, and wouldthermal decomposed into different crystalline Ga2O3heterojunctions, then research thephotocatalytic activity about these thermal decomposition products. The study foundthat with the increase of temperature, the crystal type of Ga2O3obtained by thermaldecomposition changed from gamma phase to beta phase, their photocatalytic watersplitting activity could achieve a maximum value, when formed heterojunction withrelatively suitable ratio between gamma phase and beta phase. In addition, we alsostudied to doping the Fe and V into the parent compound, the experimental results showthat Fe is difficult to successfully doped in such conditions, while V could besuccessfully.