Preparation And Characterization Of Nitrogen Or Phosphorus Doped Carbon As Supercapacitor Electrode

Three-dimensional porous activated carbon, due to the advantages of low cost, long cycle life, large specific surface area, has wide application prospect in preparation of super capacitor materials. However, the capacitance of pure activated carbon is limited because it only rely on the electric double layer capacitance, which limits the development of the energy density. Here, we prepared the heteroatom-doped three-dimensional porous activated carbon by using different nitrogen precursor which introduces N and P in the carbon substrate surface after etching and carbonization of precursor under high temperature. The study proved that the modified carbon material with good hydrophilicity and proper porosity which provides a more effective ion channels, and the overall electrochemical performance was improved after introducing faradic capacitance at the same time.The three-dimensional porous nitrogen doped activated carbon was obtained by KOH etching at high temperature under nitrogen protection with nitrogen-rich precursor PPy/PAn which prepared through the simple static chemical oxidation method. This study discusses the influence of different temperature on the electrochemical properties of products before and after carbonization. The experimental results show that the specific surface area is up to 1753 m2g-1 at the best temperature 700°C, and its XPS tests indicate a nitrogen content of 3.13 %.As the temperature increases, the nitrogen content decrease along with its order degree.Ionic liquids rich in nitrogen was for the first time used as a doping agent applying to the preparation process of super capacitor, and small molecules glucose was employed as carbon source. In addition, what makes the material different here is using the eutectic salt KCl- Zn Cl2 as pore-forming agent instead of KOH, the product named NCG(N-doped carbonized glucose) was obtained at 800°C under nitrogen atmosphere for two hours. Experiment results show that materials without adding ionic liquid is not good enough to the one which contain ionic liquid. It is worth mentioning that the eutectic salt belongs to the physical etching which mainly plays a role of placeholder effect, and the pore-forming ability is relatively lower compared with KOH chemical etching.We use solid-solid mixed grinding method for the preparation of NCC(N-doped carbonized cyclodextrin) which employ small molecule dicyandiamide as nitrogen precursor, cyclodextrin as carbon source and KOH as etching agent, respectively. different temperature was also studied on the electrochemical performance. For comparison, carbon materials without nitrogen was prepared at the same conditions, and named CC. The results show that NCC has a better performance and the best etching temperature is 700°C.Phytic acid, which is green and environmental, was used as P doping agent as well as structure guide agent. P doped three-dimensional porous activated carbon was achieved by applying glucose as carbon source and F127 as the soft template after high temperature carbonization. Results show that after adding phytic acid, the three dimensional structure looks like branches shape. The charge transfer resistance is much lower than materials without phytic acid doping, and the specific capacitance calculated by CVs increase more than 103 Fg-1. The capacity retention is as high as 90 % after charging and discharging for 4000 times at the current density of 1 Ag-1 in 1M KOH electrolyte.Finally, the P and N co-doping material GO/PA/PPy was obtained by using phytic acid crosslinked with graphene oxide(GO) and polypyrrole(PPy) under the process of hydrothermal and static chemical oxidation. Here we studied the effect of different content of PPy on the properties of composite materials and found that GO can delay the degradation of the PPy because its good mechanical properties, while PPy plays an important role which contribute its excellent electrical conductivity as well as pseudocapacitance behavior to the composite material. After adding different dosage of PPy(0.1, 0.5, 1 m L py), the experimental results show that the best amount of Py is 1 ml, at which the electrochemical properties of the composites is the best. The CV curves shows a rectangle-like shape in 0.5 M sulfuric acid solution with good electrochemical reversibility as well as good electrical conductivity and large specific capacity.