Preparation And Research Of Ru/C Supercapacitors With Activated Carbon Prepared From Hemp Rods As The Carrier

Supercapacitor is a promising energy storage device because of its large charge/discharge efficiency,high power density and long cycle life compar e to ordinary lithium battery.Supercapacitor has great potential for application in the field of mobile communication,electric vehicles,electronic devices and aerospace,which require high-power pulse power supply.Ruthenium oxide has become the hot research topic because it has extremely high theoretical specific capacitance and good conductivity.But it is not suitable for large scale commercial application because of its high cost.So it is the primary task to find suitable materials combined with ruthenium oxide as composite electrode materials for reducing the amount of ruthenium oxide and improving the specific capacitance of supercapacitors.In our work,we have studied the preparation of hemp stem activated carbon and ruthenium oxide/carbon composite electrode materials.At the same time,we have carried out the research on the electrochemical properties of ruthenium oxide/carbon composite materials in supercapacitors to provide evidences both in theory and experiment for studying mechanism of supercapacitors.In this paper,hemp stem was used as raw material to obtain biomass hemp stem activated carbon by calcining and removing the organic matter in the stem.Ruthenium oxide was loaded on hemp stem activated carbon and assembled into supercapacitors.The effect of activated carbon with different pore size dis tribution and specific surface area on electrode materials was studied.The results were as follows:1?The third chapter reported the production of activated carbons?HSACs?obtained by NaOH activation derived from waste hemp stem.The HSACs prepared by ratio of NaOH:char?W/W?equal to 3:1?HSAC-3?presented the optimum BET surface areas was 2116.06 m²g^-1 and a reasonable pore size distribution.Ruthenium oxide/HSAC-3 composite materials were synthesized by chemical coprecipitation method.The electrochemical properties of ruthenium oxide/HSAC-3 composite electrode materials were tested through the cyclic voltalmmetry?CV?and constant current charge method.The results showed that the area specific capacitance of the composite material is up to 708.29 mF/cm²,5?internal resistance,and its capacitance retention was 92.3%at 1000 cycles.2?The ruthenium oxide/carbon composite electrode materials were prepared by using the HSAC prepared by NaOH:char equal to 3:1 as a carrier and four different alkali solutions as precipitants.The XRD results showed that the samples were all amorphous.The samples were also analyzed by SEM and EDS.The results showed that sample prepared by tetramethylammonium bicarbonate were sm all and uniformly distributed on the surface of HSAC-3.The XRD results show that ruthenium oxide gradually changed from amorphous to crystalline with the increase of drying temperature.After electrochemical test,the results showed that the area specific capacitance of the composite material that dried by 120?is up to 863.85 mF/cm².At same time,its electrochemical performance decreased with increasing crystallinity.3?The XPS test was performed on the electrode materials of supercapacitors with different KOH electrolyte concentrations after testing the cyclic voltammetry curve.The results showed that the capacitance may consists of three parts:1)The pseudocapacitance produced by Ni?OH?₂ participating in the electrode reaction;2)The pseudocapacitance produced by a very fast sequence of reversible faradaic redox,electrosorption or intercalation processes on the surface of electrode material ruthenium oxide.3)Double layer capacitance.With the electrolyte concentration increased,its electrochemical performance were improved.When the electrolyte concentration was 0.5mol/L-3mol/L,the double layer capacitance was the main component of the total capacitance.When the electrolyte concentration was 3mol/L-6mol/L,the total capacitance increased,and the ps eudocapacitance produced by the reversible faradaic redox accounts for the main part.