Ternary Cu-Mo-S Nanostructures: Controllable Synthesis, Structure Characterization And Catalytic Properties

The State Council of China published "The National Medium-and Long-Term Program for Science and Technology Development (2006-2020)" in 2006 and it listed nanotechnology as one of the Major Scientific Research Programs, as well as protein science, quantum regulation, growth and reproduction research. The program will promote the development of nanomaterial science largely. As we all know, nanomaterials perform a lot of unique properties, such as small size effect, specific surface effect, quantum effect and Coulomb blockade effect. As a result, they attract amount of interesting and are widely applied in electron device, energy conversion and storage, environmentology, catalysis, biological medicine, and so on. Among them, binary layered transition metal sulfides, such as MoS2, are especially important and becoming hot topic after the sucessf of graphene. In contrast to binary one, the ternary layered transition metal sulfides Co2MX4 (M=Mo, W; X=S, Se) have more parameters that can be tunable, thus exhibit more unique properties, i.e. interesting square lattice, distinct band structure, fascinating catalytic performance, etc. Therefroe, it is very important for both fundamental research and specific applications to realize the controllable synthesis of Ci2MX4, analysize its accurate atomic structure and expore the potentials.In addition, because high brightness and continuous wide spectrum, synchrotron radiation light sources are known as "magic lamp of science and technology" and they play important roles in physics, chemistry, biology and material science. What’s more, synchrotron radiation based X-ray absorption fine spectroscopy is a powerful method for material structure analysis and the explaination Physical and chemical properties.In this thesis, we are focousing on the controllable synthesis, formation mechanism investigation, structure characterization at atomic level of ternary Cu2MoS4 nanostructures. The potential applications of Cu2MoS4 in photocatalysis and electrocatalysis are also discussed. The main results are following:1. Several Cu2MoS4 nanostructures were prepared by using Cu2O copper source and template, including nanosheets, nanopartieles, hollow nanostructures. The influence of chemicals, solvent, reaction time and other parameters was also analysized.2. The accurate structure of I-Cu2MoS4 nanosheet was characterized at atomic level by Rietveld refinement, high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine spectroscopy (XAFS). The atomic model was subsequently built up based on the lattice parameters.3. The formation mechanism of I-Cu2MoS4 nanosheet was deeply explored by ex-situ XRD, SEM and TEM analysis. We found that Kirkendall effect, oriented growth and Ostwald ripening played significant roles in the formation of I-Cu2MoS4 nanosheets. In addition, the transition of P-Cu2MoS4 to I-Cu2MoS4 was discovered and analysized.4. The photocatalytic and electrocatalytic performances of various Cu2MoS4 nanostructures were investigated systematically. The relationship between micro-structure and catalytic property was also discussed.