| This paper focuses on the preparation of waste carbon-based composite materials and the performance in supercapacitors.The bagasse and industrial waste liquid containing graphene oxide are selected and prepared into electrode materials by hydrothermal method.The morphology and structure of the prepared materials were characterized and tested for electrochemical performance.The relationship between the structure and electrochemical properties of the materials was discussed.The research contents are as follows:1.Firstly,porous carbon was developed as an electrode material by simple hydrothermal method,and its morphology and structure were characterized.The electrochemical properties of the electrode as a supercapacitor and lithium ion battery electrode were studied.Porous structure has an effect on the electrochemical properties of the material.It not only accurately inherits the natural carbon skeleton structure of bagasse,but also achieves co-doping of nitrogen and sulfur.After the hydrothermal treatment and activation,the bagasse not only maintains its natural three-dimensional skeleton structure,but also produces a hierarchical porous structure uniformly distributed from ultramicropores to macropores,and has an ultra-high specific surface area.The BET surface area is 2419 m2g-1.The addition of thiourea in the hydrothermal process successfully achieved one-step doping of both nitrogen and sulfur,with N and S contents of 10.3 wt%and 13.9 wt%.The doped porous carbon exhibits excellent energy storage properties as an electrode material of a supercapacitor and a lithium ion battery.As a supercapacitor electrode,it has a specific capacitance of 312 F g-1 in a 6 M KOH electrolyte.As a battery negative electrode,it showed a capacity of 621 m Ah g-1 at 100 m A g-1 and a capacity of 310 m Ah g-1 at 1000 m A g-1.And its unique graded porous structure shows excellent rate performance and excellent cycle stability.The effect of graded porous structure and co-doping on the electrochemical performance improvement is that:(1)Three-dimensional hierarchical porous structure has a high specific surface area,which can shorten the ion diffusion distance,and can provide a sufficiently large electrode/electrolyte interface to achieve fast charge and discharge.(2)The stable skeleton structure effectively buffers the volume expansion of the electroactive material during charge and discharge.The tubular wall and the staggered pores can serve as channels for electron transport,which increases the stability of the material structure;(3)Doping improves conductivity and allows electrons to be transferred quickly during fast or long periods of charge and discharge,which also greatly improves cycle stability.2.Secondly,for the industrial waste liquid containing graphene oxide,it is recovered by flocculation precipitation with Zn O colloid,and the graphene/zinc oxide composite material(r GO/Zn O)is further obtained by hydrothermal treatment.The application of this carbon-based composite in supercapacitors is also discussed.The results show that when the waste liquid containing graphene oxide is mixed with the Zn O colloid,it becomes a floc.Even the Zn O colloid with a concentration of only 0.1%has an effective flocculation effect on graphene oxide.It is known by morphological characterization that Zn O nanorods are not only uniformly distributed on the graphene sheet structure,but also self-assembled to form a periodic ordered structure between the obtained r GO sheets.The formation of Zn O nanorods effectively prevents the stacking of the graphene sheet and increases the specific surface area of the material.Electrochemical testing of the electrode material as a supercapacitor showed a specific capacity of up to 175 F g-1 with excellent rate performance and cycle stability.After 5000 cycles,the capacitance of the electrode maintained 89.6%of the initial capacitance.It indicates that the recovered graphene waste liquid is promising for reuse in the field of supercapacitor energy storage. |
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