Preparation And Modification Of Doped Porous Carbon And Its Application In Supercapacitors And Pollution Removal From Waste Water

Nowadays,energy is the basic requirement for survival and a good environment is in strong demand to enjoy a healthy lifestyle.Thus,the development of high efficiency and eco-friendly materials and new energy devices and the design of novel adsorbents for contaminated water treatment are two keys to address these two needs.Porous carbon materials have the advantages of environmental friendliness and low cost,and are widely used in supercapacitors,adsorption,and catalysis.Due to its own characteristics such as high specific surface area,high stability,high electron transport capacity,easy modification and flexible structure,doped porous carbon materials have proved to be a promising electrochemical material.Not only can it be used as an excellent negative electrode material for supercapacitors,it can improve the properties of porous carbon by doping heteroatoms,and thus improve the energy storage performance and adsorption performance;it can also be expanded in the field of positive electrode materials of supercapacitors and electrocatalysts by in-situ loading of transition metal elements;Porous carbon materials modified by multi-functional groups also exhibit excellent performance in adsorption.According to reported works,the preparation of porous carbon materials still faces some problems:the preparation processes cost a lot and cause secondary pollution;the difficulty to control pore structure;the means to synthesis and control its structure are rough and need to be developed.Therefore,it is of great significance to develop new methods for preparing porous carbon materials.This research mainly developed a simple and green hydrothermal method to prepare a series of porous carbon nanosheets.And characterized its structure and application performance in supercapacitors and adsorption,the main works are summarized as follows:?1?Using lactose and magnesium nitrate as raw materials to prepare nitrogen and oxygen co-doped porous carbon nanosheets.A series of porous carbon nanosheets were successfully prepared through simple hydrothermal and carbonization steps.In order to explore the mechanism of this reaction,determine the optimal preparation method and explore the universality of the preparation method,parallel experiments were carried out on the adjustment of the raw materials ratio,carbonization temperature and different raw materials.The doping of heteroatoms is beneficial to increase the pseudocapacitance and reduce the electrode/electrolyte interface impedance,and thus improve the power density.As the carbonization temperature increased,the content of heteroatoms decreased.Except for lactose,this type of porous carbon nanosheets can be successfully prepared with glucose,sucrose,and maltose as carbon sources.The specific surface area of Mg-0.7-?-0.5-600?-HNO₃ sample is 1407 m² g^-1,which has the best comprehensive electrochemical performance(specific capacitance 300 F g^-1,high current charge and discharge property,good conductivity and long cyclic life).The results of the successful preparation of porous carbon materials with other sugars as raw materials provided a new universal method for the preparation of doped porous carbon.?2?From the perspective of improving the practical application of the device,it is a key to build an asymmetric supercapacitor and increase its operating voltage window to improve the energy storage capacity.In order to prepare asymmetric supercapacitor cathode materials,nitrate?nickel nitrate and copper nitrate?and lactose were used as raw materials to prepare transition metal oxide modified porous carbon nanosheets.The study found that the transition metals were embedded on the surface of the carbon matrix in nanoscale oxide particles forms;the materials had a high specific surface area,rich in hierarchical pores.The electrochemical tests showed that Cu-1-?-0.5-600?-HNO₃ sample could be used as a negative electrode material for supercapacitors,with a specific capacitance of 293 F g^-1 and excellent rate performance;Ni/Cu-0.5-?-0.5-The 600?-HNO₃ sample combined the dual advantages of high specific surface area and the introduction of nickel.When a transition metal element?especially nickel element?was introduced,the pseudocapacitance would increase a lot.The specific capacitance of Ni/Cu-0.5-?-0.5-600?-HNO₃ sample as a positive electrode material for supercapacitors reached up to 4402 F g^-1.Compared with bulk nickel-based electrode materials,the atomic utilization rate of nickel can be greatly improved.?3?Considering that porous carbon is directly used as an adsorbent,the advantage of high specific surface area cannot compensate for the weak interaction force with adsorbate.Therefore,a porous carbon template with high specific surface area was prepared,and then cross-linked amino-rich polyethylenimine was introduced to modify it.Under the optimal adsorption conditions,the adsorption capacity towards hexavalent chromium was 229 mg g^-1,and the adsorption capacity towards Congo red even reached 1057 mg g^-1.The adsorption process for hexavalent chromium was an exothermic process,following the pseudo-second-order model and Langmuir model.The main force of adsorption came from electrostatic interaction and chelation between functional groups and chromium species.In addition,the introduction of amino functional groups also converted hexavalent chromium into trivalent chromium with low toxicity,which greatly improved the efficiency of the removal of Cr?VI?from contaminated water with N-PCNS@PHCP.Generally,this work focused on the preparation of porous carbon nanosheets using nitrates and saccharides as raw materials.After in-situ doping of nitrogen and oxygen atoms,modification of transition metal oxides,and surface modification with amino-functional polymer,its application performance in the field of supercapacitors and adsorption were greatly improved.