| At a time of increasing global consumption of fossil fuels and worsening environmental pollution,looking for new technology and materials to develop sustainable new clean energy becomes especially important in recent years.In recent years,new hydrogen energy and lithium/sodium ion batteries with high energy density,high capacity and long cycle characteristics have been used to replace traditional fossil fuels as green and sustainable new energy,attracting increasing research.Molybdenum based functional materials,such as MoO3,MoS2 and MoSe2,have a variety of phase structures and rich chemical properties,and are ideal candidates for energy storage and conversion.However,the further development of molybdenum-based functional materials is often restricted by the shortcomings of low intrinsic conductivity,few active sites and poor structural stability.Around these key problems,this paper modified the molybdenum based functional material from four aspects:photocatalyst material composite,metal atom intercalation,surface monatomic modification and material structure and morphology control.At the same time,with the combination of synchrotron radiation X-ray absorption spectrum,X ray photoelectron spectroscopy and Raman spectrum as well as theoretical calculation methods,the improvement of battery performance in catalytic reaction process of molybd-based functional materials was investigated in depth.The main research contents and achievements are as follows:1.A simple hydrothermal method was used to prepare 1T' MoS2@g-C3N4 composite nanosheet in situ.The cocatalyst MoS2 was proved to be metallic phase by various characterization methods.The results of photocatalysis test showed that the hydrogen production rate of 1T' MoS2@g-C3N4 nanosheets was 26 times and 83 times higher than that of semiconductor phase 2H MoS2@g-C3N4 nanosheets and g-C3N4 nanosheets.The photoexcited carrier separation efficiency is significantly improved,indicating that charge transfer kinetics in metal phase 1T' MoS2 is a key parameter to further improve its performance as a catalyst.The correlation results provide a new way for the synthesis of novel high efficiency catalyst and related applications.2.A single platinum atom is doped into the ultrathin metallic phase molybdenum disulfide by hydrothermal process.Experimental results showed that the performance and cyclic stability of Pt-1T' MoS2 in acidic medium were significantly improved.Combined with TEM images,XAFS analysis and DFT calculation,it was found that doped Pt atoms were anchored on the surface of the layer bonded with S atoms.These Pt monatoms adsorbed on the surface and then captured H+ from the solution as the key active center.This work provides an idea for the study of single atom doping structure in hybrid catalysts and lays a foundation for the design of multiple active sites to effectively improve catalytic activity.3.Tin atoms were intercalated into the layers of molybdenum trioxide nanoribbons by simple water bath method,which kept the original morphology and structure stability of two-dimensional materials,and the layer spacing increased.The interaction between Sn atom and ?-MoO3 material and the bonding coordination environment were deeply analyzed by X-ray absorption spectroscopy.Combined with the structure simulation,it was found that Sn atoms interact with oxygen atoms in ?-MoO3 layers and bond with five oxygens to form a unique five-coordination structure(Mo-O-Sn-O-Mo).MoO3-Sn nanosheets exhibit excellent Li+charge and discharge performance and high cycle stability,mainly due to the fact that the Sn intercalation not only expands the layer spacing,but also improves the conductivity of the materials,make the lithium ion can rapid transmission between the layers,and the structural stability is increased to enhance the indicators of the LIBs.The results provided a new ideas for the design of new 2D intercalated materials.4.A semi-open hollow structure of MoSe2 embedded in nitrogen-doped carbon matrix was designed and synthesized by CVD selenation.The unique hollow structure not only enables elevated electrode/electrolyte interaction and rapid electron transport,but also inhibits volume expansion.Applied to the anode material of sodium ion battery,it has excellent cycle and rate performance.It has the high specific capacity of 431 mAh g-1 at the current density of 200 mA g-1,and retains the 87.7%specific capacity after 120 cycles.Notably,the 199.1mAh g-1 discharge capacity is maintained even at the ultra-high current density of 20 A g-1.Fast Na+storage can be achieved.The research results open up a new way to realize the negative electrode of high power ion battery. |
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