2.2 The synthesis of electrode material
2.2.1 The preparation of PPy nanotubes
PPy nanotubes were manufactured by the easy template oxidation procedure. 3.75 mM of methyl orange and 25 mM of pyrrole (Py) were added to 150 mL of DI water, and then stirred for 0.5 h (labeled as solution A). The FeCl3·6H2O (with the same molar amount as Py) was added in 50 mL of DI water (labeled as solution B). Afterward, gradually mix solution B and solution A, stir for 10 min, and then place in a -4 ℃ refrigerator to stand for 24 hours. The PPy nanotubes were then filtered multiple times and cleaned with DI water and anhydrous ethanol till the filtered solution was transparent, removing organic and inorganic impurities from the sample. The PPy nanotubes were dried in an oven for 24 hours at a temperature of 60 °C.
2.2.2 ZMOP cathode material
The preparation process of the ZMOP nanowires composite is shown inFigure1 . Firstly, 0.8848 g KMnO4 and 1.6 g Zn(NO3)2 are dispersed in 50 mL DI water, then 2 mL 98% H2SO4 is added, and solution A is obtained after stirring for 15 min. Then, 20 mg, 40 mg, and 60 mg of PPy were dispersed in 20 mL of DI water to get solution B. Finally, solution B was dispersed in solution A, and after stirring for 30 min, the mixed precursor was moved to the polyvinylidene fluoride lining (100 mL) , and then transferred to the stainless steel autoclave. The sealed autoclave heated for 3.5 h and kept at 140 °C. After cooling to room temperature, clean with DI water, and finally dry in a vacuum oven at 70 °C to successfully obtain ZMOP-x (x indicates different contents (2, 4, 6) of PPy).
2.2.3 PCNTs anode material
The PCNTs were prepared by using the method reported in the literature.17-19