| With the development and utilization of clean energy,biomass has received widespread attention because of its clean,renewable,degradable and diverse nature.China is a large agricultural country,adequate and reasonable use of waste biomass can not only bring more economic benefits,but alsosolve a series of environmental problems caused by the incineration of biomass waste.Biomass porous carbon materials are widely used as soil improver,pollutant adsorbent,electrode materials of supercapacitor and other new energy storage devices due to their rich sources,eco-friendly,adjustable pore structure,large specific surface area,acid and alkali resistance,corrosion resistance and excellent electrical conductivity.In this study,the waste lotus seedpod shell was selected as the biomass material,and the pore structure and carbonization degree of the porous carbon materials were controlled by changing the activator species?KOH,K2CO3,NH4H2PO4,ZnCl2?,the quality ratio of the lotus seedpod shell to the activator and the carbonization temperature.Ulteriorly,electrochemical performances of the prepared porous carbon as electrode material of supercapacitor were studied and conformed the optimum parameters for preparing porous carbon materials with different activators.Futher more,the relationship between the structure and electrochemical properties of porous carbon materials was explored.The major research results are as follows:?1?The electrochemical properties of the porous carbon derived from lotus seedpod shell prepared with KOH,K2CO3,NH4H2PO4 and ZnCl2 as activators all increased first and then decreased with the increase of activator ratio and carbonization temperature.When the mass ratio of the lotus seedpod shell to KOH was 1:2 and the carbonization temperature was 800°C,the prepared porous carbon material exhibited the best electrochemical performance.When K2CO3 was used as the activator,the optimum parameters for preparing porous carbon was that the mass ratio of the lotus seedpod shell to the activator was 1:3 and the carbonization temperature was 800°C.When NH4H2PO4 was used as the activator,the prepared parameters of the materials which exhibited best electrochemical performance was that the mass ratio of the lotus seedpod shell to the activator was 1:2,and the carbonization temperature was 600°C.When ZnCl2 was used as the activator,the optimum parameters for preparing porous carbon were that the mass ratio of the lotus seedpod shell to the activator was 1:2,and the carbonization temperature was 600°C.Under the optimal preparation conditions,the prepared porous carbon materials with different activators presented optimal specific capacitances of 203,361,365 and 256 F g-1 at a current density of 0.5A g-1.After 5000 charge/discharge cycles,the capacitance retention of the four materials was87.5%,88.0%,84.0%and 95.0%.?2?Scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy and Nitrogen adsorption and desorption were used to analyze the surface morphology,crystal structure,surface functional groups,specific surface area and pore size distribution of the porous carbon materials with the best electrochemical properties prepared by different activators.The specific surface areas of the four porous carbon materials with the best electrochemical properties were 1916.8 m2 g-1,1955.1 m2 g-1,1029.9 m2 g-1 and 1828.8 m2 g-1,respectively.The pore volumes were 0.973 m3 g-1,1.020 m3 g-1,0.513 m3 g-1 and 1.223 m3 g-1,respectively.Among them,HPC-2-800 and PPC-2-600 were mainly microporous structures,CPC-3-800 exhibited both micropores and mesopores,and ZPC-2-600 mainly consisted of mesoporous structures.Compared by the electrochemical performance,the results indicated that the electrochemical performances were obviously effected by the specific surface area and pore volume of the material.When the specific surface area was almost the same,the micropores were better than the mesopores to increase the specific capacitance of the material.When the micropores were the main pore structure,the small amount of mesopores have little effect on the electrochemical performance.When the specific surface area were almost same,a small amount of hetero atom doping has little effect on the material specific capacitance value.The porous carbon derived from lotus seedpod shell in this study has excellent electrochemical properties as the electrode material of the supercapacitor,and provides experiamental data for rational utilization and preparation of biomass porous carbon from waste biomass resources such as lotus seedpod shell. |
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