Study On The Fabrication And Properties Of Nanoporous Gold/MnO₂ Films

In recent years,supercapacitors have attracted significant atention,mainly due to their high power density,long lifecycle,and bridging function for the power/energy gap between traditional dielectric capacitors and batteries.Supercapacitors have a broad range of applications in energy storage system,consumer electronics,hybrid electric vehicles and industrial power and energy management.Nanoporous gold?NPG?with a large internal surface and excellent conductivity,is a promising electrode material for supercapacitors when combined with pseudocapacitor materials,such as MnO₂.In this paper,the preparation,thermal stability and electrochemical properties of NPG and NPG/MnO₂ films were studied.?1?Dealloying is a corrosion process during which an alloy is‘parted'by the selective dissolution of the most electrochemically active of its elements.Delloying of Au₅₀Ag₅₀ films in 65 wt.%HNO₃ begins with the disolution of Ag and the evolution of three-dimensional porosity,followed by ligament coarsening due to the diffusion of Au atoms.The average pore diameter of prepared NPG film is 36nm,with approximately3.2at.%Ag remnants.With the decrease of nitric acid concentration,the corrosion rate of Ag atoms and the diffusion ability of Au atoms are correspondingly reduced.?2?NPG/MnO₂ films were prepared by liquid phase deposition and atomic layer deposition?ALD?,repectively.The crystalline structure of MnO₂ coating prepared by liquid phase deposition is?-MnO₂,with poor crystallization.The specific capacitance of the NPG/MnO₂ film prepared by liquid phase deposition reaches 470F/g at a current density of 100?A/cm².It shows good stability?95%capacitance retention after 4000cycles test?when the deposition time is less than 30 min.Uniformly dense and amorphous MnO₂ coating can be prepared by atomic layer deposition,while the specific capacitance reaches 253F/g at a current density of 100?A/cm².It also has excellent stability?98%capacitance retention after 4000 cycles test?.Flexible NPG-MnO₂-30min film was fabricated using PET film as substrate.Forward bending at any angle does not decrease the capacitance of prepared film.When reverse bending angle exceeds 30°,the capacitance declines significantly.?3?Thermal treatment will coarsen the pore and ligament of NPG.NPG films start coarsen at 300?in N₂ atmosphere.Seperated Au particles form at 600?.The diffusion ability of Au atoms is stronger in Ar atmosphere,as the formation of Au particles can be observed at 500?.The coating of MnO₂ will improve thermal stability of NPG films.Coarsening of NPG films is restrained at 500?,while Au particles will still form at 600?.