Research On Phytic Acid-assisted P/O Co-doped Porous Carbon Material To Improve Supercapacitor Performance

In recent years,the demand for energy has increased greatly,but the supply of fossil fuels alone will lead to the rapid depletion of energy storage and be harmful to the ecological environment.Therefore,the academic and industrial circles pay extensive attention to the new energy storage equipment,focusing on various key parameters of the equipment,such as service life,power density,service temperature range and so on.Supercapacitor（SCs）has many advantages,so it has become one of the new energy storage devices.Among them,carbonaceous materials with ideal pore structure/specific surface area,good wetting/conductivity and excellent surface chemical properties show great potential and advantages in SCs.Generally,the raw materials for the preparation of carbon materials are more expensive,and the manufacturing processes are also more complex.Sometimes even in the manufacturing process will cause certain pollution to the environment.Therefore,in this dissertation,bio-friendly potato starch was selected as the raw material,and the P/O co-doped nano-porous carbon materials was synthesized with the aid of phytic acid,which is helpful to improve the supercapacitance performance.At the same time,the commercial microporous carbon was modified successfully by using phytic acid as P/O dopant.On this basis,the electrochemical properties of SCs were further improved by adding appropriate redox additives in the electrolyte.The related results are as follows:1.Biomass potato starch,gelatin and chitosan were selected as carbon sources respectively.Phytic acid was introduced to achieve the effect of activation and doping,and the carbon products were synthesized with the help of freeze-drying process.Through electrochemical tests,it was found that potato starch has more potential as a SCs electrode material,and there was an optimal ratio of phytic acid to potato starch.At this point,the characterization test is passed,it was found that the P/O doped porous carbon materials were successfully synthesized by a simple way.And the P and O content reached 1.79 at%and 17.56 at%,respectively.Thus the wettability and pseudo-capacitance of carbon material can be improved.In addition,the specific surface area of the material is 798 m²g^-1,and the pore volume is 0.30 cm³g^-1.In the two-electrode system with 1 M H₂SO₄as electrolyte,when the current density is 1Ag^-1,the specific capacitance reaches 172 F g^-1and the rate performance reaches 69.8%.The capacitance retention rate is 85.7%after 5000 cycles at a current density of 4 A g^-1.When the power density is 5000 W kg^-1,its energy density can reach 4.0 Wh kg^-1.It can be seen that it is very feasible to use biomass as carbon source and select appropriate activator as a combination of green and environmental protection in SCs.2.Using phytic acid as dopant,P/O modification on the surface of commercial microporous carbon materials was realized by post-treatment and calcination,and the structure of carbon materials was effectively adjusted.Specifically,with the high content of heteroatoms,the porosity and contact angle are decreasing but the conductivity become much larger.Furthermore,p-aminophenol is introduced to serve as redox additive,which can produce more active surface sites by forming hydrogen bond and complexation with the surface functional groups,further supplying additional pseudocapacitance.The results show that the energy density of carbon sample by phosphorus/oxygen doping in 1 M H₂SO₄electrolyte with p-aminophenol is as high as9.2 Wh kg^-1,which is 2.6 times that of pristine carbon.In addition,because of its simple operation and effective manner,the integration of surface modification towards carbon materials and appropriate redox additive could be suitable for largely enhancing the supercapacitor performance.