Controllable Preparation Of CdS-based Nano-heterojunctions And Their Photocatalytic Hydrogen Production Performance

In today's society,energy shortages and environmental pollution are two major problems that need to be solved urgently.It has made the development of efficient,environmentally friendly and renewable clean energy a hot topic.Photocatalytic hydrogen production technology has become one of the many options to stand out,and has become the focus of research for many researchers.CdS nanomaterials have become a nanomaterial with great prospects for photocatalytic hydrogen production due to its suitable energy band structure and wide optical absorption range.However,its CdS itself has a higher recombination rate of photogenerated electrons and holes,and the photo-corrosion of sulfides hinders its large-scale development and application.The main purpose of this thesis is to use CdS nanowires as the research object,and modify it in various ways to achieve the purpose of improving photocatalytic hydrogen production activity and light corrosion resistance.?1?Facile preparation of Z-scheme CdS-Ag-TiO₂ composite for the improved photocatalytic hydrogen generation activityThe Ag nanoparticles and TiO₂ nanoparticles were sequentially loaded on the CdS nanowires in different ways to form a Z-type nanomaterial of CdS-Ag-TiO₂ to improve the photocatalytic activity of CdS.Compared with CdS-TiO₂ and pure CdS nanowires,the superiority of CdS-Ag-TiO₂ is highlighted.The photocatalytic hydrogen production performance is 2.45 times that of pure CdS,and the photocatalytic hydrogen production activity is the best.It can be known by TEM,XRD,UV-via,PL,etc.that it can not only expand the light absorption range through Ag nanoparticle,but also can change the electron transport direction as an electron mediator,so that it can obtain efficient charge separation rate and significant Light corrosion resistance.This chapter is mainly to provide a new research approach to the Z-type heterojunction structure based on CdS nanowires.?2?Preparation of 1D/2D core-shell structure CN-CdS and its photocatalytic hydrogen production performanceThe two-dimensional structure of g-C₃N₄ was directly wrapped on the surface of CdS nanowires by a one-step method to form a special g-C₃N₄-CdS?CN-CdS?core-shell structure,thereby exploring the improvement of CN-CdS.By preparing a series of CN-CdS reaction products,it was found that the photocatalytic activity of CN-CdS-100 complex formed by the reaction of 1 mmol CdS nanowires with 100 mg g-C₃N₄ reached 1.99 times that of pure CdS nanowires,which is the best.Hydrogen production rate.Under the reaction conditions of CN-CdS-100,although the light absorption range did not increase significantly,the thickness of g-C₃N₄ was moderate,and the size of the exposed mesopores was large,so that the g-C₃N₄ and CdS were accumulated by the conventional heterojunction.The electrons at the interface have a relatively sufficient reaction site,and the photogenerated holes are transferred to the surface of g-C₃N₄ to obtain excellent photo-corrosion resistance.The main innovation of this chapter is to open up a research idea of using one-step method to prepare CN-CdS core-shell structure.?3?Study on photocatalytic hydrogen production of CdS nanowires enhanced by surface modification of MoS₂ nanosheetsThe CdS-MoS₂ composite?CM?was prepared by hydrothermal method of loading MoS₂ nanosheets on the surface of CdS nanowires.MoS₂ was used as a cocatalyst to replace precious metal Pt to enhance the photocatalytic activity of CdS nanowires.After preparation and testing of different proportions of CM composite nanomaterials,it was found that when the reaction ratio of CdS to MoS₂ was 0.3,the photocatalytic activity of the formed CM-0.3 complex reached 35.8 times that of pure CdS?no precious metal Pt loading?.Even better than the optimal ratio of CdS-Pt-5?the reaction product of 5 mg Pt precursor and 1 mmol CdS nanowire?.In the CM-0.3composite,the MoS₂ distribution is relatively uniform and can fully expose the surface of the CdS nanowire,reducing the shielding effect of the MoS₂ nanosheet.Moreover,the connection of CdS and MoS₂ with type I heterojunction greatly enhances the intensity of CdS in the visible region,and utilizes its highly efficient charge separation to achieve a significantly enhanced photocatalytic hydrogen production activity and effective light suppression of CM composites.The purpose of corrosion.The main innovation in this chapter is to find out the possibility of replacing the precious metal Pt with MoS₂ nanosheets and the difference between the two under the optimal reaction ratio.