Prepation Of Carbon Materials By Solvothermal Method And Its Supercapacitor Performance

Supercapacitor as a sort of energy storage system are the most promising reserve force compared to chemical batteries on the basis of their superior power density and good cycle life.At present,carbon materials have become the most widely used electrode material in commercial supercapacitor devices.In this paper,a series of carbon based materials were prepared by solvothermal method.The porous carbon materials with different heteroatom doping,different morphologies and structures,and different pore size distribution were obtained by the experimental design.The electrochemical properties of carbon based materials with different morphologies and structures were investigated by cyclic voltammetry and charge discharge tests,the effects of doping,morphology,specific surface area and pore size distribution on the performance of carbon based supercapacitors were studied.We reveal the relationship between the doping of heteroatom,the structure of nanomaterials with their electrochemical properties.The details and results are summarized as follows:(1)Here we report a different strategy to synthesized the nonaligned BCN nanotubes and vertically-aligned BCN nanotube arrays(VA-BCNNT)by simple low temperature solvothermal route.The results of electron microscope and XPS revealed that the resultant nanotubes are made up of B,C,and N species with the hexagonal structure,And the length and diameter of nanotube is 2?m and 250 nm,respectively.Electrochemical testing results indicated that VA-BCNNT has the highest electrochemical performance.(547 F g-1 at the current density of 0.2 Ag-1)That shows doping B?N atoms in carbon and orderly structure can greatly to improve the electrochemical properties of carbon materials.(2)We employ nitrogen doped carbon microspheres(CM-N)and nitrogen,fluorine co-doped carbon microspheres(CM-NF)as electrodes,which were prepared by a simple low-temperature solvothermal route without post-processing.The results of SEM and elemental mapping showed the smooth surface and nearly-perfect spherical geometry and quantify a uniform distribution of C,F,and N species within CM-NF spheres.The results of electrochemical measurement showed that CM-NF has the highest volumetric capacitance(521 F cm-3 at the current density of 0.2 Ag-1).The electrode exhibits excellent electrochemical stability without loss of specific capacitance after 10000 cycles,indicating a long-term stability of the electrode.The results of in-situ XRD and SEM showed that the CM-NF electrode does not produce new compounds during charge discharge process.Finally,the results of DFT show that the co doping of nitrogen and fluorine can greatly improve the electrical conductivity of the electrode material,which is helpful to improve the electron transition and the capacitance of CM-NF in the electrochemical process(3)The carbon nitride precursor with high density was prepared by solvothermal method,and then the nitrogen doped activated carbon with different specific surface area and pore size distribution was prepared by controlling the amount of KOH.Through XPS and BET test,we can see that the addition of KOH can not only affect the proportion of nitrogen in the material,but also has an important influence on the structure and morphology of activated carbon.Through the results of electrochemical test,When the KOH and carbon nitrogen precursor mass ratio is 0.5(MAC-N-0.5)as the electrode materials,showing the highest gravimetric capacitance and volumetric capacitance(385F g-1 and 573 F cm-3 at the current density of 0.2 Ag-1),at the same time,the rate capacitive performance of the MAC-N-0.5 reaches an ultrahigh value of 86.3% at a high current density of 20 A g-1(495F cm-3)and after 10000 cycles,the capacitance is almost no loss,showing a long-term stability.A series of two-electrode symmetrical supercapacitor prototypes were assembled by using MAC-N-0.5 as electrode material,a high volumetric energy density of 13.5 Wh L-1 at a respectable volumetric power density of 12.1 KW L-1 is achieved,indicating that the device has a high power performance,which is a promising energy storage device.(4)By solvothermal method,a kind of carbon material containing high nitrogen was easy large prepared using single organic solvent acetonitrile as raw material.The process is simple and the by-products can be recycled.A porous carbon nitride material(N-AC)was prepared by chemical activation of precursor carbon nitride materials.BET and XPS tests showed that the prepared N-AC had a properly pore structure,and the doped nitrogen was mainly in the form of pyridine nitrogen(N6)and pyrrole nitrogen(N5).N-AC and commercial activated carbon were used as electrode materials for supercapacitors.The electrochemical measurements showed that the volumetric capacitance was 454 F cm-3 and 143 F cm-3 with a current density of 0.1A g-1.It can be seen that the volumetric capacitance of N-AC capacitor is nearly 3 times than the commercial activated carbon,and after 10000 cycles,the capacitance of the N-AC is almost no loss,showing a long-term stability.Due to the simple synthesis method and excellent electrochemical performance,N-AC is expected to be a new type of supercapacitor electrode material instead of commercial activated carbon.