Nitrogen Doped Graphene/Carbon Nanotube/Nickel Composites By Solide-state Pyrolysis And Its Performance Of Supercapacitor

GrapHene, a single atomic layer of sp~2-bonded carbon atoms arranged in a honeycomb lattice, which was considered as the ‘mother of all carbonforms. In addition to its planar state grapHene can be ‘wrapped’ into zero-dimensional spHerical buckyballs, ‘rolled’ into one-dimensional carbon nanotubes, or ‘stacked’ into three-dimensional grapHite. GrapHene has drawn tremendous scientific interests for its high specific surface area, high thermal conductivity, fast charges carrier mobility, high light penetration and strong Young’s modulus. Besides grapHene composites also show excellent pHysical and chemical properties and are viewed as the future leader of electronic materials. At present, the methods of grapHene preparation have many shortcomings for mass production, for example high pollution, high cost, sop Histicated process and so on. Therefore, bulk synthesis of grapHene or hetero-atom doping of grapHene by a simple, controllable, green and low-cost metod is still a critical target in scientific and industrial research. In this paper, we have successfully synthesised the grapHene composites by a new method and applied it for symmetrical supercapacitor electrode materials, which exhibited unique electrochemical properties. The specific work and results were as follows:1. The nickel pHthalocyanine were easily prepared upon exposure to microwave irradiation in the presence of ammonium molybdate. The nitrogen-grap Hene/carbon nanotube/nickel composites were successfully produced in bulk by pyrolysis of nickel pHthalocyanine in an Ar atmospHere. The preparation method of nitrogen doped grapHene composites was novel, simple, high efficiency, low pollution and less cost. The PH, nickel content as well as the pyrolysis temperature of the nickel pHthalocyanine had a great influence on the morpHology and proportion of nirogen-grapHene. The pyrolysis process have been entirely completed at 800℃ comparing to the temperature at 600℃; in alkaline conditions, nickel could easily play a role of catalyst, and make it growing into carbon nanotubes; the nitrogen-grap Hene was thinner when less nickel was contained in precursor; along with the increase of nickel content, the carbon nanotubes became thinner and increased in number accordingly.2. In contrast, p-toluene sulfonic acid as catalyst similarly, the nitrogen-grap Hene /carbon nanotube/nickel composites were also produced through the pyrolysis process of pHthalocyanine nickel precursor. Compared with using ammonium molybdate catalyst, the yield of composites was higher, the composites possessed the thinner nitrogen-grapHene, less quantity of carbon nanotubes, fewer impurities and more stable structure. Under p-toluene catalyst precursor, 800℃was still good for reaction; the quantity of carbon nanotube was a little more in alkaline conditions than acidic conditions; nickel was suspected to be a kind of square type.3. The nitrogen-grap Hene/carbon nanotube/nickel composites were used as symmetrical supercapacitor electrode materials and tested by cyclic voltammetry test and galvanostatic charge-discharge measurements in a two-electrode system using 6M KOH as electrolyte. The electrode materials treated by acid showed a poor reversibility and stability, for the first discharge specific capacity up to 2809F/g, but after 200 cycles given to 308F/g; the electrode materials treated by alkaline had excellent reversibility, high charge-dischareg efficiency and good stability, and the specific capacity was 175F/g after 3000 cycles.