Effect Of Nano SiO₂ On The Structure And Electrochemical Properties Of PDPP-Based Porous Carbon Materials

Supercapacitor is an emerging class of high-power energy storage devices.Due to its greater power density,excellent reversibility and longer cycle life compared with batteries.It can also depicted extremely large current densities in a short period of time compared to conventional electrostatic capacitors exhibiting higher current density.However,the energy density of these supercapacitors is relatively low that could be improved via two ways:1)to increase the specific capacitance of the electrode materials and 2)to increase the working voltage of the capacitor.Herein,we have synthesized heteroatoms(O,N,P)doped porous carbon materials to enhance specific capacitance of working electrode.We synthesized porous carbon materials by using poly[bis(aryloxy)phosphazene](PDPP)as a carbon precursor,SiO2 as a template.SEM,XRD,XPS,Raman,nitrogen adsorption and desorption were performed for structural,crystal phase,elemental and porosity evaluations of the as-synthesized materials,respectively.The performances of these materials were tested via electrochemical investigations.The detailed experiment contents are as follows:1)We regulated the mass ratio of nano-SiO2 and poly[bis(aryloxy)phosphazene]to adjust the pores numbers in the carbon materials as well as the pore size distribution.Experimental results showed that by adding 5 percent of SiO2 in poly[bis(aryloxy)phosphazene](2g)that the specific capacitance of the as-synthesized carbon materials significantly enhanced(435 F/g at 0.5A/g current density).Afterwards,the specific capacitance increases followed by a slight decrease up on increasing contents of SiO2.Moreover,the specific capacitance of the sample SPC/20-800-600 is 427 F/g at 0.5A/g current density is obtained when at a specific ratio 20:100(SiO2:poly[bis(aryloxy)phosphazene]).2)We further selected SPC/5 and SPC/20 with superior electrochemical performances to explore the influence of temperature on the preparation of porous carbon materials.We found that the specific surface area was associated with carbonization temperature.For example,at 600 ? the sample SPC/20-600-600 showed specific surface area reaches to maximum value of 3132 m2g-1.The SPC/20-600-600 demonstrated higher values of 482 F/g and 261 F/g at 0.5A/g current density when tested via three-electrode system and two-electrode system,respectively.3)We also studies the effect of in-situ synthesis on the electrochemical properties of the carbon materials.We performed the in-situ synthesis of SiO2 by using tetraethyl orthosilicate(TEOS),tetrahydrofuran(THF)and PDPP and obtained carbon materials through carbonization,etchition and activation.The as-obtained highly porous carbon materials depicted excellent electrochemical properties(480 F/g at 0.5A/g current density).