Preparation Of Copper Indium Sulphide Composite Photocatalyst And Study On Its Water Splitting Performance Under Visible Light

Since human beings experienced the second scientific and technological revolution,fossil energy,as the main energy supply for social and economic development,has had a great negative impact on the living environment of human beings and organisms.Photocatalytic splitting of water by solar energy to produce hydrogen is considered as one of the ideal technologies to solve human energy crisis and environmental crisis in the 21st century.In the system of photocatalytic splitting of water and hydrogen evolution,the key to efficient utilization of solar energy lies in the selection of suitable photocatalyst.Photocatalysts play an important role in the absorption of visible light and the separation efficiency of photo-generated charges in the solar energy conversion hydrogen energy system.CuInS₂（CIS）,as an important ternary sulfide direct bandgap semiconductor,has attracted extensive attention of researchers due to its narrow bandgap（E_g=1.5-1.9 eV）,wide light absorption range and no heavy metals.However,I-III-VI ternary sulfide generally has photoetching effect in the photocatalytic process,and its photocatalytic activity and stability need to be further improved.In order to overcome the defects of CIS in photocatalytic system and improve its hydrogen evolution performance of photocatalytic splitting of water.In this paper,the photocatalytic system is mainly constructed by looking for suitable cocatalyst and CIS,and the photocatalytic efficiency of CIS semiconductor materials is improved by broadening the light response range and improving the separation efficiency of photo-generated charges.A series of experimental methods and characterization methods were used to study the structural properties,photocatalytic activity and optical properties of CIS photocatalytic composite materials.The main research contents of this paper are as follows:（1）A 2D/2D photocatalytic system with BP nanosheets as cocatalysts and CIS as photocatalysts was prepared by hydrothermal and mechanical compounding method for efficient photocatalytic splitting of water.AFM,SEM,TEM,XRD and XPS were used to analyze its morphology,crystal structure and chemical properties.The experimental results show that under visible light,the photocatalytic system constructed by loading different proportions of BP nano-sheets on CIS nano-sheets has better hydrogen evolution performance than CIS monomer.The 5BP-CIS composite photocatalyst showed the best hydrogen evolution activity up to 2.02 mmol·g^-1·h^-1.After hydrogen evolution cycle stability test,it also showed good stability.The analysis of a series of experimental results shows that the addition of BP nanosheets can broaden the light absorption range,enhance the separation efficiency of photogenerated carriers,and improve the catalytic activity of the composite catalyst.（2）A homogeneous solution is prepared by urea and a solution containing metal nickel and cobalt ions.NiCo-LDH is prepared as a cocatalyst by thermal decomposition reaction at 90℃,and CIS is prepared as a catalyst by hydrothermal method.The two materials were hydrothermally compounded at 120℃to prepare nanocomposites.The morphology,crystal structure,chemical and optical properties of NiCo-LDH,CIS and NiCo-LDH/CIS nanocomposites were analyzed by SEM,TEM,PL,XRD and XPS.Photocatalytic hydrogen evolution experiments were carried out on the nanocomposites prepared by compounding different contents of NiCo-LDH and CIS.The results showed that NiCo-LDH/CIS nanocomposites containing NiCo-LDH（30 wt%）showed the best hydrogen evolution performance of 4.43 mmol·g^-1·h^-1 and had good stability.Analysis of experimental results through mechanism investigation shows that the addition of NiCo-LDH can broaden the light absorption range,enhance the separation efficiency of photogenerated carriers and improve the catalytic activity of the composite catalyst.（3）In order to further optimize the hydrogen evolution performance of NiCo-LDH/CIS photocatalytic system,WO₃ nanomaterials were prepared by a simple hydrothermal method to construct NiCo-LDH-CIS/WO₃ Z-scheme heterojunction.When the mass ratio of CIS/WO₃ is 4:1,the photocatalytic hydrogen evolution performance is the best(17.57 mmol·g^-1·h^-1),which is nearly 4 times higher than that of NiCo-LDH/CIS photocatalytic system.The analysis of a series of experimental results shows that the addition of WO₃ and CIS can construct effective heterojunction and enhance the separation efficiency of photo-generated charge.The photocurrent and impedance spectra further verified the mechanism of photogenerated charge separation.At the same time,CIS/WO₃ is a 2D/2D photocatalytic system,which is conducive to improving the stability of the photocatalyst,reducing light corrosion and agglomeration,forming close interface contact and promoting charge transfer.The establishment of the system can provide a novel idea for designing an efficient and energy-saving artificial photosynthesis system.