Controllable Synthesis Of Porous Carbon Based On Benzoxazine Chemistry

Porous carbon materials have been widely used in catalysis, energy storage, adsorption, and drug delivery, due to the unique properties such as high surface area, good chemical stability and electrical conductivity. At present, it is difficult to control the structure and surface chemistry of porous carbon in nanoscale, so it is necessary to prepare porous carbon with controlled structures efficiently. In our previous work, we have developed the synthesis of porous carbon based on the benzoxazine chemistry, which can be designed with flexible molecular structure, introducing nitrogen-containing functional groups in situ. So, the thesis will further develop the design synthesis and application of different new types of porous carbon based on the benzoxazine chemistry:1. A new synthesis of highly uniform polymer and carbon nanospheres with precisely tailored sizes and high monodispersity has been established. Polymer nanospheres are first synthesized through precisely programming the reaction temperatures, using monomers including resorcinol, formaldehyde,1,6-diaminohexane (DAH), and in the presence of surfactant Pluronic F127. The correlation between the initial reaction temperature (IRT) and the nanosphere size fits well with the quadratic function model, which can in turn predict the nanosphere size at a set IRT. The nanosphere sizes can be easily tuned (250-105nm for polymer nanospheres,225-95nm for carbon nanospheres). The polybenzoxazine based nanospheres that can be carbonized with little shrinkage to produce monodisperse carbon spheres with controlled porosity and surface chemsitry. The porous carbon spheres contain intrinsic nitrogen-containing groups that make them more useful for CO2adsorption. The CO2adsorption capacity can reach11.03mmol g-1at-50℃and～1bar, which is highly desirable for the CO2separation from natural gas feeds during the cryogenic process to produce liquefied natural gas. During the CO2adsorption process, the porosity plays an essential role in achieving high CO2adsorption capacity at ambient pressure, while the nitrogen content of the carbon adsorbent is a booster for CO2adsorption capacity at low pressures. This finding may be beneficial to design sorbents for the separation of dilute CO2-containing gas streams in practical applications.2. The assembly of commercial silica colloids in the presence of1,6-diaminohexane and their subsequent encapsulation by poly(benzoxazine) have been used to produce coral-like porous carbons. Pyrolysis of the polymer followed by the removal of the silica produces a carbon with a continuous skeleton that contains spherical medium-size pores as "reservoirs" with a structure similar to a bunch of grapes. The total volume and the diameter of the "reservoir" pores are tunable. The coral-like morphology and the pore structure of the carbons make them suitable for the encapsulation of SnO2nanoparticles as electodes for lithium ion storage. The electrodes show a high specific capacity and good cycling stability, i.e.,900mA h g-1after50cycles of charge-discharge.3. Graphene-based mesoporous carbon sheets were synthesized as substrates for high power lithium-ion battery assisted by diaminohexane, which plays a crucial role in fabricating the sandwich morphology by linking the pore-forming silica colloid onto structure-directing graphene oxide and initiating the polymerization of benzoxazine on their surfaces. Pyrolysis of the polymer followed by the removal of the silica produces uniformly distributed spherical mesopores on the carbon-graphene sheets. Such mesoporous carbon can serve as rigid nano-confinement reservoirs to support and control the particle size of the active component, thus allowing the fast lithium-ion diffusion. Besides the high conductivity and diffusivity through the continuous porous carbon-graphene framework, this sheet structure facilitates the Li+and electrons transfer through the layer and contributes toward the enhanced kinetics during the operation. The LiFePO4C electrode supplied by the prepared carbon sheets exhibits a stable and high reversible capacity of166mA h g-1at0.1C and116mA h g-1at20C. Furthermore, the cell retains93%of its initial capacity at20C over1000cycles.