Preparation And Properties Of Doped Three-Dimensional Graphene Materials

As a material with special properties,graphene has attracted much attention due to its great performance and revolutionary changes in many fields.However,due to its large specific surface area,graphene often causes the layers to be stacked together,which reduces its own adsorption capacity,and also affects the excellent performance of graphene,which in turn affects the performance improvement of graphene materials.Moreover,such superposition and agglomeration are irreversible unless an external force such as strong agitation or ultrasonic is applied to make the dispersion more uniform.In this paper,two-dimensional graphene sheets are self-assembled into a three-dimensional macrostructure to solve the agglomeration problem of graphene,and at the same time,doping of hetero atoms is realized,and the capacitance value is further improved.In this paper,a simple,rapid and efficient preparation method of three-dimensional graphene hydrogel is used to realize the surface functional modification of graphene during the reduction process,and it is used as the electrode material of supercapacitor.The effect on electrochemical performance.Preparation method of hetero atom-doped three-dimensional graphene hydrogel:synthesizing graphite oxide by Hummer method,obtaining graphene oxide by operation of graphite oxide,reducing graphite oxide by chemical reduction method using three different types of reducing agents based on graphene oxide.The olefin is self-assembled into a three-dimensional graphene hydrogel by van der Waals force and?-?stacking to realize the reduction of graphene oxide.The specific research contents are as follow:1.A reduced graphene oxide hydrogel having a three-dimensional porous structure was prepared by chemical reduction method using dimethyl sulfoxide?DMSO?as a reducing agent in an aqueous solution of ammonia.The prepared DRGHs is not only considered to be an ideal electrode material for supercapacitors,but also the doping of heteroatoms can increase the electrochemical performance by increasing the tantalum capacitance.Different amounts of reducing agent were added and the resulting DRGHs exhibited different electrochemical properties in the supercapacitor.With the increase of the amount of reducing agent,DRGHs showed better specific capacitance.DRGHs-1,DRGHs-2 and DRGHs-3 had very good capacitance performance at 0.2 A g^-1,and the specific capacitance was as high as 313.6,323.6 and 348.0 F g^-1,respectively.It also shows that the DRGHs based electrodes have good stability and high reversibility in the charge/discharge cycle test.That provides a strategy to significantly improve the capacitance characteristics of RGHs by controlling the different doping of heteroatoms.2.Reducing graphene oxide aerogels?RGOHs?with three-dimensional porous structure were prepared by chemical reduction method using aminothiourea?NSRGOHs?and aminourea?NRGOHs?as reducing agents.The prepared RGOHs are not only considered to be a promising supercapacitor electrode material,but also nitrogen-sulfur double doping or nitrogen doping can improve the electrochemical performance by increasing the faraday tantalum capacitor.The optimized samples were prepared by controlling the mass ratio of graphene oxide?GO?to aminothiourea or aminourea to 1:1,1:2 and 1:5,respectively.Different amounts of aminothiourea or aminourea are added,and the resulting RGOHs exhibit different electrochemical properties in the supercapacitor.As the amount of reducing agent increases,RGOHs have a better specific capacitance.In addition,the capacitive performance of nitrogen and sulfur double-doped NSRGOHs is superior to that of pure nitrogen-doped NRGOHs.NSRGOHs exhibit excellent capacitance at 0.3 A g^-1,with specific capacitances up to 232.2,323.3 and 345.6 F g^-1;NRGOHs exhibit good capacitance at 0.3 A g^-1with specific capacitance up to 220.6,306.5 and 332.7F g^-1.3.Three-dimensional sulfur-doped graphene aerogels were prepared by chemical reduction in a graphene oxide?GO?aqueous solution using three sulfur-containing compounds?sodium sulfite,sodium hydrogen sulfite,sodium sulfide?as reducing agents and dopants?SGAs?.An optimized sample was prepared by controlling the mass ratio of each reducing agent to graphene oxide.The effects of the amount of reducing agent on the degree of reduction of SGAs and the amount of sulfur doping were studied.The sources,doping forms and electrochemical properties of S were analyzed,and their electrochemical properties were studied.Studies have shown that as the amount of reducing agent increases,the sulfur content gradually increases and the oxygen content gradually decreases.SGAs-t has the highest sulfur content of 10.72%;the lowest oxygen content and higher specific capacitance.The specific capacitance is as high as 61%at a current density of 0.5-20 A g^-1.Due to the abundant porous structure,fast ion channel and low sulfur function of electrochemical energy storage,the prepared SGAs have a high specific capacitance and can provide an energy density of more than 10 Wh Kg^-1.In addition,it has also been shown that SGAs have good electrochemical stability and high reversibility in charge and discharge cycle tests.