Fabrication And Electrochemical Properties Of Nanoporous Copper /Manganese Dioxide

Nanoporous copper（NPC）with 3D homogeneous porous architecture was prepared by fast cooling and free dealloying.The NPC-supported MnO₂ composite was prepared by the reduction of KMnO₄ by anhydrous ethanol on NPC substrate.NPC substrate with large specific surface areas and excellent electrical conductivity can effectively improve the utilization of MnO₂ surface active sites and promote MnO₂ chemical reactions.This research mainly focused on preparing NPC1,NPC2 and NPC3 via dealloying of amorphous Cu₅₀Zr₅₀,Cu_47.5Zr₅₀Nb_2.5 and Cu_47.5Zr₅₀Ag_2.5 alloys in the 0.5 mol/L HF solution respectively,and subsequently fabricating the composite electrodes of NPC and MnO₂.The phase,morphology and element composition were characterized by the X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）.The electrochemical performance was tested by cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy.The result shows that NPC1 with a ligament/pore size of 45 nm are successfully synthesized by dealloying the Cu₅₀Zr₅₀ metallic glasses in 0.5 M HF for 10 min.It is found that the uniformity and length scale of ligaments/pores can be tuned by simply alloying 2.5at.%Nb or Ag to the Cu-Zr binary glassy alloys.NPC substrate with large specific surface areas can effectively improve the utilization of MnO₂ surface active sites and promote the specific capacitance of MnO₂/NPC composite.With the increase in the mass ratio of NPC1for the composite material,NPC1 efficiently leads to the lower charge transfer resistance(R_ct)and the higher electrical conductivity of the composite electrode.The morphology of MnO₂ transforms from aggregated particles to nanoflowers.The particles disperse better and utilization of MnO₂ surface active sites is improved.NPC2 and NPC3 show more fine and uniform ligament/pore structure than NPC1.MnO₂/NPC1,MnO₂/NPC2 and MnO₂/NPC3 composites display high specific capacitance values of 403,593 and 505 F/g,respectively,at the scanning rate of 2 mV/s.