Study on the Preparation and Properties of MIn2S4 (M=Zn、Ca、Mg、Co) Photocatalytic Materials

Author:Zeng Chao

Supervisor:hu ying mo huang hong wei

Database:Doctor

Degree Year:2019

Download:39

Pages:109

Size:7974K

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In order to retard the increasingly serious greenhouse effect and solve the energy shortage problems,generation hydrogen by photocatalytic water splitting and photocatalytic reduction of CO2 into clean fuels has received extensive attention and research.ZnIn2S4、CaIn2S4 and CoIn2S4 are reported as semiconductor photocatalysts with visible light response.A new semiconductor photocatalysts CoIn2S4 is developed firstly.The prepared MIn2S4(M=Zn,Ca,Mg,Co)semiconductor material can decompose water to produce hydrogen or reduce CO2under visible light.In view of the poor photocatalttic activity of MIn2S4,in this thesis,MIn2S4 was modified by carbon doping,solid solution fabrication and constructing heterojunction to improve their photocatalytic activity.The specific research contents are as follows:(1)MgIn2S4,MgIn2S4-Cx and MgIn2S4-SC were prepared via hydrothermal reaction and low temperature sintering reaction.The test results showed that,for MgIn2S4-Cx sample,both bulk-doped carbon and surface-coated carbon exist,while the MgIn2S4-SC sample was only coated with carbon on the surface.The photocatalytic reduction of CO2 activity of MgIn2S4-Cx and MgIn2S4-SC samples was greatly improved compared to MgIn2S4.MgIn2S4-C2 has the highest photocatalytic activity,and its CO production rate is 20.5 times that of MgIn2S4sample.The CO production rate of MgIn2S4-SC is only 8.03 times that of MgIn2S4.The reason why MgIn2S4-Cx samples possess superior photoctallytic activity can be summarized in these three points as follow,high separation migration efficiency of photogenerated charge,strong visible light absorption and strong CO2 adsorption ability.In addition,by contrasting and analyzing the photocatalytic performance differences between MgIn2S4-C2 and MgIn2S4-SC samples,It can be deduced the function of bulk-doped carbon is to inhibit photogenerated charge recombination and promote charge separation and transfer,while the main role of surface-coated carbon is to enhance CO2 adsorption performance.(2)The crystal systems of ZnIn2S4 and CaIn2S4 prepared by the same method are trigonal and cubic,respectively.ZnXCa1-XIn2S4(x=0.8,0.6,0.4,0.2)solid solution are prepared.The CO2 photocatalytic reduction experiments show that all ZnXCa1-XIn2S4 solid solutions exhibit better photocatalytic activity than ZnIn2S4 and CaIn2S4.In all solid solutions,Zn0.4Ca0.6In2S4exhibited the best photocatalytic performance,the CH4 and CO evolution rate of which is 16.7and 6.8 times that of ZnIn2S4,and 7.2 and 3.9 times that of CaIn2S4,respectively.Compared with ZnIn2S4 and CaIn2S4,with the dcreasment of x value,the potention of conduction band first become more negative and then become positive,which is different from the change law of the conduction band potential in general solid solution.In addition,another heterogeneous solid solution,ZnXCd1-XIn2S4,was synthesized,and the conduction band potential of the solid solution was also more negetive than that of ZnIn2S4 and CdIn2S4.(3)A Core-shell structure heterostructural photocatalyst CoIn2S4/MgIn2S4-x with close contact was developed by using MgIn2S4 as the self-sacrificed template to produce CoIn2S4.CoIn2S4/MgIn2S4-2 sample exhibited the best photoctalytic activity among CoIn2S4/MgIn2S4-x composite photocatalysts.The CH4 evolution rate of CoIn2S4/MgIn2S4-2 sample was 7.3 and2.1 times that of MgIn2S4 and CoIn2S4,respectively.(4)A series of x CoIn2S4/g-C3N4 composite photocatalyst was synthesized by in-situ crystallizing CoIn2S4 nanospheres on the matrix of g-C3N4.30%CoIn2S4/g-C3N4 sample has the highest photocatalytic activity,and its H2 generation rate was 5.2 and 23.9 times that of g-C3N4 and CoIn2S4,respectively.It is indicated that the construction of heterojunction structure can promote charge separation and promote photocatalytic performance.