Fabrication Of Hierarchical Porous Carbon And Controlling Strategy Of Its Structure

Because of the outstanding adsorption and desorption performance, good chemical stability, high mechanical strength and strong corrosion resistance, activated carbon has been widely used in adsorption, separation, catalysis, energy storage and other fields. With the development of science and technology, it is urgent to improve the properties of activated carbon. Activated carbon pore structure adjustment is the key to improve the performance of activated carbon. In the present work, catalytic activation together with physical activation were used to control the pore structure of the commercial coal tar pitch- based activated carbon and the effect of the amount of catalyst on the pore structure were investigated; three-dimensional hierarchical porous structures were constructed using the industrial grade of spray drying technology. Electrochemical capacitors were built and the relationships between microstructures of the electrode materials with characteristics of energy storage were discussed based on the principles of double-layer.Catalytic activation together with physical activation were used to control the pore structure of the commercial coal tar pitch based activated carbon. Results show that adding Fe?NO₃?₃ together physical activation can efficiently widen the pore size distribution of the commercial activated carbon and raise its mesopore ratio, and thus enhance the adsorption capacity of. Whether the activating agent is CO₂ or steam,the resulting activated carbons have the best pore structure with highest mesopore ratio?67% and 65%, respectively? and biggest average pore diameter?5.6nm and 5.4nm, respectively?. Activating agent also has effect on the adjustment of pore size distribution. Activated carbon activated by steam has higher Methylene blue value compared to the activated carbon activated by CO₂ although they have the same mesopore ratio, which indicates that Ferric salt together with steam activation can improve the adsorption capacity of activated carbon more efficiently.Sulfonated pitch was used as a precursor for hierarchical nanoporous carbons by spray drying,stabilization, carbonization and KOH activation step-by-step. The resulted carbon has a large BET surface area more than 2300 m2 g-1 and the electrodes made of it have an excellent rate performance when used in a symmetric capacitor with 6 M KOH and 1M TEA-BF4/PC as the electrolytes. Remarkable electrochemical performances are obtained when the electrode use the hierarchical nanoporous carbon named SPs-70-2. When the electrolyte is KOH, the capacitor exhibits a high specific capacitances of 340 F g-1 at a current density of 0.05 A g-1 and still 225 F g-1 at a current density of 100 A g-1. When the electrolyte is TEA-BF4/PC, the capacitor exhibits a high specific capacitances of 170 F g-1 at a current density of 0.05 A g-1 and still 115 F g-1 at a current density of 10 A g-1. Furthermore, the capacitor containing SPs-70-2 also had excellent power and energy properties. When the power density is up to 25 KW kg-1, its energy density still maintains 24.16 Wh kg-1. Besides, the morphologies, the morphologies, carbonaceous structures and pore textures of the hierarchical porous carbon microspheres were also analysed. The results show that the activated carbons not only have a good spherical structure, but also have a continuous pore structure varying from micropore to macropore. Additionally, experimental results show that developing spherical inter-connected architectures in nanoporous carbons by spray granulation is an effective way to improve the electric conductivity, and thus improve the utilization of the specific surface area.