Preparation And Electrochemical And Electromagnetic Wave Absorption Properties Of Hierarchically Porous Carbons

With the rapid development of science and economy,energy sources and environmental problems have received more and more attention and the demands for new materials have also increased.Based on such advantages as high specific surface area,low density and good physicochemical stability,hierarchically porous carbon(HPC)materials have been widely used in supercapacitor,capacitive deionization,electromagnetic wave absorption and gas adsorption.Recently,the preparation and application of HPC have been rapidly developed,but the selection of precursor and the design of controllable structure are still the key factors restricting the development of HPC.Therefore,this dissertation focuses on the preparation,structure design and application of HPC.The main contents are as follows:(1)Utilizing the structural advantages of the conventional high internal phase emulsion,the polyHIPE with higher specific surface area can be obtained by adjusting the volume ratio of divinylbenzene/toluene in the organic phase of emulsion system.The water droplets in the dispersed phase of emulsion system act as macroporous templates.The micro/mesoporous structures result from the radical hypercrosslinking reactions and porogens.During the activation process,the macroporous framework of emulsion template can be well retained while plenty of micro/mesoporous structures are introduced by adjusting the mass ratio of activator to precursor.Finally,HPC with three dimensional interconnected porous structure is obtained.The synergistic effects of high specific surface area and hierarchically porous structure endow the resulted HPC with excellent electrochemical performance,including a high specific capacity of 319 F/g and a superior electrosorption capacity of 21.3 mg/g in 500 mg/L NaCl solution.(2)HPC derived from emulsion-templated polymer precursor with controllable structure and specific surface area is prepared by adjusting the volume ratio of water/oil phase in emulsion system and the mass ratio of activator during the carbonization process.Thanks to the enhancement of polarization abilities and multi-reflection of microwave simultaneously induced by hierarchical pores,the obtained HPC exhibits outstanding microwave adsorption performances,including the maximum reflection loss of-56.4 dB at 11.5 GHz and an effective adsorption bandwidth of 6.0 GHz at the thickness of 2.46 mm.The rational structure design of HPC leads to remarkable microwave absorption performance and the relationship between pores with diverse scales and MA performance is investigated thoroughly,which can serve as a significant guidance for the design of porous MA materials.