Chitosan Based Heteroatom-Doped Hierarchical Porous Carbon Materials And Their Electrochemical Performance

The progress of science and technology has led to the widespread use of electronic products,and it places higher demands on the development requirements of energy storage devices.Supercapacitors have a lot of advantages such as fast response time,excellecnt cycle performance and wide operating range.However,commercial carbon-based supercapacitor electrode materials face two bottlenecks:limited capacitance and high cost.Chitosan is the second abundant biomaterial which derives from organisms such as crabs,shrimp shells and algae.Chitosan are rich in nitrogen-containing groups and thus can be used to develop highperformance electrode materials for supercapacitor.In this work,chitosan is used as carbon and nitrogen sources.We have fabricated highperformance supercapacitor electrode materials by heteroatom-doping and constructing hierarchical porous structures.Heteroatoms can improve the wettability of electrode materials and enhance pseudocapacitance by participating in redox reactions.Micropores provide large number of active adsorption sites,while mesopores and macropores provide fast diffusion channels for electrolyte ions.Heteroatom-doped hierarchical porous carbon materials exhibits excellent electrochemical performance due to the synergy of heteroatom and hierarchical porous structure.First of all,chitosan-based N-doped carbon materials were prepared by freeze-drying and carbonization treatment.The influence of different heat treatment temperature on the structure and properties of N-doped carbon materials was investigated.The results shows that NC-800 possesses a high nitrogen content.NC-800 shows a high specific capacitance of 171 F g-1 at a current density of 0.5 A g-1.It also exhibits nearly 100%retention of initial capacitance after 10,000 cycle,which shows the stability of nitrogen-containing groups.On the basis,N-doped hierarchical porous carbon materials were obtained by one-step pyrolysis of the Zn-chitosan aerogels.Research results shows that the porous structure of Ndoped hierarchical porous carbon materials become developed with the increase of heat treatment temperature,and structure and morphology of samples could be controlled by adjusting the ratio of Zn-chitosan complex.The optimal sample NHPC-5 exhibits a high specific surface area of 932 m2 g-1 and its pore volume is 0.76 m3 g-1.NHPC-5 exhibits a high capacitance of 230 F g-1 at 0.5 A g-1 and maintains almost 100%of the initial capacitance after 10,000 cycles.The synergy of heteroatom and hierarchical porous structure leads to excellent electrochemical performance of NHPC-5.In the end,Nitrogen and Boron doped hierarchical porous carbon materials were prepared by hydrothermal treatment.Research results hydrothermal treatment could further improve the wettability of electrode materials,and also enhance charge storage performance thorough redox reaction.Symmetric supercapacitor devices were assembled to assess the practical application potential.It possesses a high energy density of 9.6 Wh kg-1 at 123 W kg-1 which shows the excellent electrochemical performance and practical application potential.