Contrivable Synthesis And Synchrotron Radiation-based Characterization Of Multifunctional Layered Transition Metal Sulfides

As China continues to modernize and grow its economy,the resource shortage and environmental issues we face are also becoming an increasing concern.Photo/electrocatalysis,as a new type of technology,which can not only realize the generation of clean energy,but also the degradation of organic pollution,has become a great hotspot of scientific research.It is vital to design a series of photo/electrocatalysts and analyze the structure-activity relationship for the target achievement.It mainly involves two aspects:the enhancement of intrinsic activity and the construction of active sites.The analysis of the structure-activity relationship of the catalysts is inseparable from the advanced characterization techniques and theoretical calculations.Nowadays,the binary-layered transition metal chalcogenide(TMC)nanostructure,like MoS2 and WS2,has been studied thoroughly by experiment results and theoretical calculation.Compared to binary TMC materials,ternary TMC materials have the advantages of adjustable composition,controllable structure and rich electronic structure.Therefore,in-depth investigation into the controllable synthesis,structure analysis and structure-activity relationship of ternary-and multi-component TMC materials should have great scientific significance and practical application.In this paper,the application of ternary Cu2MoS4-based catalysts in photo/electrocatalysis was regarded as the main line.By carring out the strategies of morphology control,facet engineering and construction of active sites and composite structure to fully improve their photo/electrocatalytic performance;relying on advanced characterization techniques,such as synchrotron radiation X-ray absorption fine structure spectroscopy and photoelectron spectroscopy to reveal the specific structure information of the catalyst(electronic structure,atomic structure,etc.);by means of density functional theory to confirm the experimental results of the catalysis,and provide guidance and reference for the development and utilization of ternary and multi-component TMC materials.The relevant research contents and achievements are as follows:1.For the synthesis of ternary Cu2MoS4 catalysts with green and inexpensive process,we had used ethylene glycol and water as the solvent creatively.Through the solvothermal method with a template of cuprous oxide,we successfully prepared P-Cu2MoS4 nanocube with excellent crystallinity and One-dimensional I-Cu2MoS4 nanobelt.The fine structure of Cu2MoS4 nanomaterials was revealed by synchrotron radiation X-ray absorption fine structure spectroscopy.In addition,the formation mechanism of Cu2MoS4 nanomaterial with different dimensionation was also abtained.This work provides a rich experience for green and inexpensive synthesis of ternary and multi-component TMC materials.2.In order to achieve controllable synthesis of CU2MoS4,we successfully synthesized the {010} facet-exposed Cu2MoS4 nanotubular structure using a modified solvothermal method.The {010} facet-exposed Cu2MoS4 nanotubular showed obviously better photocatalytic performance(degradation and watersplitting)than the{100}-facet exposed nanoribbon structure under visible light,which even comparable to some precious metal-based photocatalyst materials.Combined with synchrotron radiation based-ultraviolet photoelectron spectroscopy and density functional theory calculations,we could conclude that the conduction band structure of Cu2MoS4 materials with different crystal planes is inconsistent,leading to huge differences in catalytic performance.This work provides experimental and theoretical basis for the research of facet engineering based on ternary or multi-component TMC materials.3.In order to construct a large number of exposed active sites,hollow Cu2MoS4 hierarcical structure was prepared by solvothermal method based on Kirkendal effect by using cuprous oxide with different morphology as templates.Compared with Cu2MoS4 nanosheets and nanoparticles,this hollow hierarcical structure exhibited smaller overpotentials and Tafel slopes,which suggested that it had greater potential advantages in HER.Based on the measurement of the electrochemically active surface area,we had found that the hollow hierarcical structure exposes more catalytically active sites.This work could be a reference for the design and synthesis of other TMC hollow hierarcical structure.4.Through the introduction of highly conductive two-dimensional graphene structure in the photocatalytic system,we prepared a closely integrated Cu2MoS4/graphene composite structure.The composite photocatalyst not only exhibited and enhanced photocatalytic degradation performance,but also improved the overall stability of the catalysts.This work developed a way for constructing hierarchical TMC architecture photocatalysts for water pollutant treatment,photocatalytic water splitting,solar cells,and other potential applications.5.In order to explore the electron transfer in complex co-catalyst system and its effect on the photocatalyst performance,a core-shell structure of ultrafine carbon layer coated Ni nanoparticle was obtained by one-step annealing method.The results of XANES and theoretical calculations collectively show that electrons from the ultra-thin carbon layer transferred to the interfaces of Ni and C.By combining with TMC photocatalysts,like CdS and Cu2MoS4,a high efficient photocatalytic system was constructed.This work provides a good reference for the development of cheap and efficient metal-based co-catalysts and the study of their related photocatalytic mechanism.