Precious Metals And Copper Sulfide Nanomaterials:Ionic Liquids-Assisted Synthesis And Applications In Catalysis

As a potential“green”reaction medium,ionic liquids（ILs）have attracted much attention owing to their incomparable advantages.ILs have broad application prospects in many fields such as organic synthesis,extraction and separation,and nanomaterial preparation.Especially in the preparation of inorganic nanomaterials,ILs exhibit many unique properties compared to conventional solvents,and are often used to prepare nanomaterials with excellent properties.Among many nanomaterials,precious metal and copper sulfide materials play important roles in many fields due to their unique physical properties such as light,heat,electricity and magnetism,especially in the field of catalysis.It is well known that the catalytic properties of precious metal and copper sulfide materials are closely related to their composition,size and surface structure.Although the preparation of precious metal and copper sulfide nanomaterials has been rapidly developed,the pursuit of more efficient,controllable and environmentally friendly preparation methods is still one of the important research directions for the synthesis of precious metals and copper sulfide nanomaterials.This project aims to prepare precious metal and copper sulfide nanomaterials by liquid phase synthesis method with virtue of the excellent properties of ILs.The main contents of the study are as follows:1.A simple,rapid and economic one-pot strategy is developed for the synthesis of3D nanoporous gold（NPG）in aqueous solution with the assistance of a functionalized IL 1-hydroxyethyl-3-methylimidazolium chloride（[HEmim]Cl）.It is shown that 3D NPG is constructed from twisted and interconnected Au nanochains with diameter of approximately 40 nm.This material has a high specific surface area of 22.77 m²g^-1and various porous structures,including macropores,mesopores and micropores.Yet,there are lots of crystal defects,such as a twin boundary,edge atoms and amorphous regions.It is demonstrated that[HEmim]Cl plays an important role in directing the growth and assembly of 3D NPG,and the IL concentration,the amount of reductant and the reaction temperature also have influences on the morphology and structure of NPG to a certain extent.Based on control experiments,a possible growth mechanism is illustrated for the formation of 3D NPG.In addition,the asprepared 3D NPG exhibits superior catalytic activities for both the reduction of p-nitrophenol and the degradation of methylene blue in water,which can be completed in 14 min and 8 min,respectively.2.A facile IL-modulated（1-butyl-3-methylimidazolium chloride,[C₄mimCl]）strategy is presented for the preparation of AuPd bimetallic nanodendrites（NDs）with hyperbranched and symmetric structures at room temperature in aqueous solution.It is shown that the alloy AuPd NDs possess multi-level architectures,that is,primary 3D large flowers with diameter of about 2.5⁴.0μm,secondary 2D leaves,tertiary symmetric branches and quaternary symmetric petals.A series of factors influencing the morphologies and properties of the products are also investigated.It is clear that both Au/Pd atomic ratios and IL 1-butyl-3-methylimidazolium chloride（[C₄mim]Cl）are crucial to the formation of 3D AuPd NDs.Meanwhile,the as-obtained AuPd NDs display outstanding catalytic activity toward both the degradation of organic dyes（methylene blue and Congo red）and the reduction of nitroaromatics（p-nitrophenol and p-nitroaniline）.More importantly,no obvious deactivation is found after six runs of the recycling experiments.3.A common IL 1-hexadecyl-3-methylimidazolium chloride([C₁₆mim]Cl)is utilized to direct the growth and assembly of porous PtPd nanoparticles（NPs）.The as-obtained porous Pt₂₅Pd₇₅ NPs have obvious hierarchical structures with nanoflowers as subunits and nanorods as basic units,large specific surface area(56.83 m²g^-1)and various pore sizes,including mesopores and micropores The tunable elemental components and structures of porous Pt₂₅Pd₇₅ NPs can be achieved by regulating the precursor ratios and[C₁₆mim]Cl concentrations,respectively.Owing to high specific surface area and porous hierarchical structures,as well as probable electronic effects between Pt and Pd,the as-prepared porous Pt₂₅Pd₇₅ NPs exhibit prominent catalytic activity and high stability than other porous NPs with different Pt/Pd ratios and commercial Pt/C for ammonia borane hydrolysis to produce hydrogen,in which the activation energy Ea and the turnover frequency value（TOF）of porous Pt₂₅Pd₇₅ NPs are calculated to be 29.06 kJ/mol and 69.76 mol _H2/mol_metal/min,respectively.4.CuS nanowalls were prepared with a hydrothermal synthesis method assisted by 1-mercapto-3-methylimidazolium bromide([C₁₀mim]Br).The prepared CuS nanowalls were systematically characterized and analyzed,and the effect of a series of factors on their morphology and structure were studied.The CuS nanowall is composed of a plurality of nanosheets having a width of 0.5².5μm and a thickness of about 36 nm,which are entangled in different directions.These flakes are composed of nanoparticles with diameter of 8²0 nm,and the whole CuS nanowalls have a thickness of about 2μm.It is found that the alkyl chain length and cationic structure of the IL play a very important role in guiding the synthesis of the CuS nanowall.In addition,the synthesized CuS nanowalls show higher catalytic activity in catalyzing the thermal decomposition of ammonium perchlorate（AP）.