Preparation And Electrocapacitive Performance Of Resin Based N-Doped Carbon Materials

Supercapacitor is considered as a promising and green device for energy storage. Among all of the electrode materials, carbon materials have gained great attention because of their high electrical conductivity, high chemical stability, and designable porous and doping structure. To satisfy the requirements of increasing the electrochemical properties of supercapacitors, doping nitrogen into carbon materials seems to be an effective route. Because it can change the electronic density and increase the active sites of carbon materials.In this work, ortho-aminophenol and formaldehyde were used as nitrogen and carbon sources, respectively. F108 was used as the surfactant. One kind of resin based N-doped carbon materials with nitrogen content of 1.67-4.79% was successfully prepared. Here, resin based N-doped carbon materials were used as the electrode materials for supercapacitors. The influence of structure properties on the electrochemical properties of supercapacitors were studied in detail through changing the preparation conditions including the amounts of NaOH and F108, the evaporation temperature, and the carbonization rate. The conclusions are as follows:1. Ortho-aminophenol and formaldehyde were polymerized to form a kind of three-dimensional polymer under the catalysis of NaOH. With the partition effect of F108, resin based N-doped carbon materials composed of nano-scale particles which adhered each other in three-dimensional space were successfully fabricated. The pore structure of this kind of carbon materials is mainly composed of meso-and macro-pores. This pore structure can provide a good physicochemical platform for studying the influence of specific surface area and doping elements on the capacitive properties. When used as electrodes, this kind of carbon materials own high specific capacity of 130 F g-1 with low specific surface area of 90 m2 g-1.2. The specific surface area and the oxygen content of the obtained carbon materials were decreased with the increase of NaOH amounts from 0 g to 0.1 g. At the same time, the nitrogen content and the specific capacity were first increased and then decreased. When the amounts of F108 varied from 0 g to 2.5 g, the specific surface area and the specific capacity of the obtained carbon materials first increased and then showed steady trend. The specific surface area and the oxygen content of the obtained carbon materials were decreased while the nitrogen content were increased with the increase of evaporation temperature from 5℃ to 40℃. As a result, the specific capacity showed a trend of first increase and then the decrease. When the carbonization temperatures varied from 1℃/min to 10℃/min, the specific surface area and the oxygen content of the obtained carbon materials were increased and the nitrogen content was decreased. The specific capacity first increased and then showed a steady trend. Thus, the electrochemical performance on supercapacitors of resin based N-doped carbon materials is influenced by the specific surface area and the contents of doping elements.3. Oxygen usually exists on the carbon surface as residue of carbon precursors. Large amounts of bridge oxygen can be found on the surface of resin based N-doped carbon materials. To further study the influence of bridge oxygen on the capacitive properties, hydrogen reduction was carried out on the N-doped carbon materials to reduce the content of surface oxygen. As a result, the surface oxygen content decreased 2.22%. However, the specific capacity decreased nearly 25%. By measuring the conductivity, surface wettability, and electrochemical impedance, we proposed that surface oxygen played an important role for the capacitive performance; though the doped oxygen reduced the electronic conductivity, on the other hand, enhanced the surface wettability and ion diffusion rate of the electrode materials.