Fabrication And Study On Nano-electrodes Of Capacitors Based On Porous Anodic Alumina Templates

Polyaniline (PANI) has often been used as electrode material for supercapacitors and has a quite prospective future. Porous anodic alumina (PAA) could be the templates when fabricating PANI nano-electrodes in order to enhance their performance. In this work, two different PAA templates were initially fabricated, then PANI nano-electrodes were successfully obtained by in-situ synthesis method and composite method by combining the templates with Fe or Ni substrates together. Besides, electrochemistry performance of the electrodes was tested and analyzed.Firstly, PAA was fabricated in oxalic acid aqueous solution by constant current hard anodization in a short period, and the relationship between the immersion time in phosphoric acid aqueous solution and the hole diameter was investigated. The results are as followed:When PAA was immersed for 15min in 5 wt% phosphoric acid aqueous solution at 30℃, whose pore diameter raised from 30 nm to 50 nm, could be used for synthesizing PANI by in-situ synthesis method; When PAA was immersed for 35 min, whose pore diameter became 75 nm, it could be separated from the substrate and used for synthesizing PANI by composite method. Then, PAA templates with large interpore distance(about 350 nm) were fabricated in a mixed solution, which contained oxalic acid and absolute ethanol, by progressive increasing voltage method and through-hole technology, the results show that:PAA template with through hole could be achieved after being immersed in 5 wt% phosphoric aqueous solution for 180 min at 30℃ and the thickness of barrier layer decreases at a rate of about 1.26 nm/min under such condition, these templates could be used for synthesizing PANI by composite method,Secondly, Ni was electrodeposited on Al substrates and then in the constant current hard anodization PAA (immersed in 5 wt% phosphoric aqueous solution for 15 min at 30℃) with different parameters. The results show that:It is reasonable when dilution ratio of nickel Watts bath and deionized water is 1:1, and voltage is-0.9 V.Thirdly, PANI was synthesized in constant current hard anodization PAA by Cyclic Voltammetry (CV) method with Ni electrodeposited in to become electrodes. The results show that:The synthesize rate in constant current hard anodization PAA is low, only about 12.5% of that directly electrodeposited Ni on Al substrate in the same situation. Besides, the capacitance fall-off rate is very high, there is little capacitance when tenth-cycle.Lastly, the technology and performance of obtaining PANI by composite method with two different substrates and two different kinds of PAA templates were compared and analyzed. The results are as followed:Fe substrate has lower synthesized speed but less fall-off rate compared to Ni substrate. The quantity of PANI obtained when using constant current hard anodization PAA templates is only 42% of that when using large interpore distance PAA templates by CV method for thirty cycles.