Study On Supercapacitor Performance Of Carbon Nanotubes Coated Zero-valent Iron And Cobaltosic Oxide

As a new type of energy storage component, supercapacitor has been widely used in modern power system and studied by more and more domestic and overseas scientists because of its advantage such as high power density, high charge/discharge speed, high cycling stability, and environment friendly. The morphologies and microstructures of electrode materials are the key factors which affect the performance of supercapacitor, and therefore, how to prepare materials which have excellent capacitance performance and enhance the capacitance value of electrode materials have become the focus of research. In order to enhance the capacity value of materials, we synthesize the composite of carbon nanotubes(CNTs) and active iron nanoparticles by a chemical vapor deposition, and the special structure Co3O4 nanomaterials by a hydrothermal-thermal decomposition method.By using organic compound ferrocene as raw material, Fe/CNTs nanocomposite was synthesized by one-step chemical vapor deposition method. Nano zero-valent irons are imbedded inside CNTs, forming a composite nanostructure. The CNTs supply a range limited environment for elemental iron which helps preventing the agglomeration of iron particle and increasing the active reaction positions between electrolyte ion and active substance. The result of electrochemistry testing shows that the Fe/CNTs composite has more obvious pseudocapacitance characteristic, and better capacitance performance than CNTs. The specific capacitance is 157 F·g-1 while 84 F·g-1 for CNTs. When the current density is 0.3 A·g-1, for the Fe/CNTs composite, the capacity remains 78% of the initial value after cycling charge/discharge for 1000 times. Considering the widely use of zero-valent iron in water treatment field, further research about the adsorption and reduction of Fe/CNTs was done. The results shows that the degradation rate of azo dye and Cr(VI) is beyond 90% under certain conditions.Flower like structure Co3O4 and hexahedral Co3O4 were prepared by changing the reaction condition of hydrothermal-thermal decomposition method. The structure characterization of materials by XRD and SEM shows that both types of Co3O4 are belong to cubic spinel structure. Two structured Co3O4 self assemble into nano-layers, and however, the nano-layers size of flower like structure Co3O4 is smaller than the ones of hexahedral Co3O4. This helps to shorten the transmission distance of electrolyte ion. The result of electrochemistry testing shows that the flower like Co3O4 has a higher specific capacitance than hexahedral Co3O4. The specific capacitance of flower like and hexahedral Co3O4 achieve 244 F·g-1 and 175 F·g-1, respectively. When the current density is 0.5 A·g-1, the hexahedral Co3O4 has better cycling stability with 14% decay after cycling charge/discharge for 1000 times.