Study On Preparation And Properties Of Nanoporous Copper And Composites Based On Cu-based Amorphous Alloys

As a new type of functional material,nanoporous metal has the characteristics of combining nanometer-sized pores and metal framework.Nanoporous composites are prepared on this substrate,which is characterized by a sandwich-like structure with multi-level pores.In addition,due to the advantages of amorphous alloys with a single phase composition,adjustable composition,and no crystal defects,nanoporous metal with adjustable pore size and uniform structure can be prepared by dealloying amorphous alloys,which are widely used in separation,filtration,catalysis,noise reduction,and heat exchange process,etc.At present,there are few reports on the post-treatment processes of nanoporous metals including(electrochemical)oxidation and sulfidation.Besides,nanoporous metal ribbons prepared by dealloying amorphous alloy are brittle and have poor mechanical properties.Therefore,based on the Cu-based amorphous alloy,this paper foused on the nanoporous copper(NPC)prepared by dealloying,and nanoporous composite prepared by combining hydroxide or sulfide on NPC substrate.The influence of dealloying technology on the morphology of NPC was studied,and the influence of post-treatment process on the microstructure and electrochemical performance of the composite was analyzed.The main research of the paper was as follows:1)Preparation of NPC with adjustable pore size by dealloying ternary Cu-Ti-Co amorphous alloy:The influence of dealloying time,solution and composition of amorphous alloy on the final size of pore and ligament of NPC has been studied.With the increase of time and concentration,the size of pore and ligament gradually increase.However,when it exceeds a certain limit,the nanoporous structure will be significantly coarsened,making the ligament thicker.At the same time,the Co element improves the distribution of size of pore and ligament,thus the NPC could be more uniform and smaller.The mechanism of dealloying is that the huge potential difference among the Cu,Ti and Co elements makes the inert Cu atoms diffuse and recombine at the metal/electrolyte interface and finally form NPC.The electrochemical results are presented as follows.The area specific capacitance is202.3mFcm^-2 at the current density of 5mAcm^-2,and the capacitance retention rate could reach 90%after 5000 cycles.When it is used as catalysts to degrade methyl orange(MO)in the dark assisted with the ultrasonic irradiation,the degradation rate of MO reaches 100%after 60 min above 60?,which is much higher than that of commercial Cu mesh(60%).Last but not least,the composite catalyst has the threshold of temperature for degradation of MO dye.2)The needle-like Cu(OH)₂/NPC composite was successfully designed based on the Cu-Zr-Ni-Be amorphous alloy by the two-step method and its electrochemical performance was studied.The three-dimensional(3D)bicontinuous NPC with adjustable size of pore and ligament was successfully prepared by controlling dealloying process(temperature and time)in 0.05 M HF and 0.5 M H₂SO₄ mixed acid.The optimal parameters under the experimental conditions were that temperature was 75?,and time was 8h.When the temperature is too high or the time is too long,the NPC ribbon will be coarsened to a certain extent,resulting in a smaller pore size.Due to the addition of Ni and Be elements,the mechanical properties of the NPC ribbon have been greatly improved.Therefore,Cu²⁺ions excited on the surface by anodizing react with OH^-ions in the electrolyte to grow in situ needle-like Cu(OH)₂ nanowires.The growth process is divided into four processes:oxidation,self-assembly,growth and re-growth.The Cu(OH)₂/NPC composite with 3D hierarchical pore structure composed of NPC layer,nano-bundle Cu(OH)₂ layer and nano-flower Cu(OH)₂ layer has a large specific surface area(130.8m²g^-1).The Cu(OH)₂/NPC composite electrode can be directly used as a working electrode without binders and conductive agents,showing typical Faraday characteristics of pseudocapacitance.The area specific capacitance is as high as 784mFcm^-2 at 3mAcm^-2,and the specific capacitance still maintains more than 96%of the initial value after 5000 cycles at 12mAcm^-2.3)Hexagonal CuS nanosheets with a thickness of 17?52nm were successfully synthesized in-situ prepared by a simple one-step dealloying method.When the concentration of H₂SO₄ solution reached 15 M,3D flower-like CuS/NiS microspheres with a diameter of about 2?m were successfully synthesized in situ on the NPC substrate.With the extension of the dealloying time,the thickness of hexagonal CuS nanosheets forming the flower-like microspheres gradually decreases.The coexistence of micro-and nano-scale pores between CuS/NiS composite greatly increases the specific surface area of the product.The formation mechanism is mainly divided into three stages:nucleation and growth of NPC,nucleation and growth of transition metal sulfides,and the collapse of flower-like microspheres.The electrochemical results of the flower-like CuS/NiS composite electrode show that the composite has the synergistic effect between battery behavior and capacitance behavior.The mass specific capacitance at 1Ag^-1 is 122Fg^-1,and the capacitance retention rate is 95%after 5000 cycles at 10Ag^-1.