Preparation And Capacitance Properties Of Heteroatom Doped Resin-based Carbon And Its Composites

Supercapacitor is a new type of energy storage device which have the advantages such as high power density,fast charge-discharge capability,long cycle life and attracted much attention.The electrodes are the key role for the development of the novel supercapacitors,and carbon materials are the top priority.Among the various carbon materials,the resin-based carbon materials are the good option for electrode materials.The resin materials are excellent precursors for the fabrication of resin-based carbon materials.For example,the resin materials with unique morphology not only were used to prepare the resin-based carbon electeodes with the special micromorphology,but also dope the resin-based carbon materials to improve the electrochemical performance of electrodes when the resin materials load heteroatoms.Thiourea and formaldehyde are common industrial raw materials and they could be condensed by acid to form thiourea formaldehyde resin（TF）.The TF chains contain a large number of N and S atoms which provide the innate conditions for the doping of the resin-based carbon materials.The thiourea formaldehyde resin-based carbon material（CTF）has amounts of the atoms of N and S.The synergy of the N and S atoms is beneficial to reduce the surface hydrophobicity and provide the pseudocapacitance by the redox reaction with electrolyte.The CTF is fitted to be supercapacitor electrode material.However,due to the low thermostability of TF,the CTF electrode materials did not achieve ideal electrochemical properties.This paper contains the following three studies to discusse how to enhance the electrochemical performance of CTF.Thiourea formaldehyde resin（HTTF）was synthesized by hydrothermal method with thiourea formaldehyde resin as precursor.The molar ratio of raw materials,reaction temperature,reaction time and the amount of catalyst were controlled during the hydrothermal process.Different CHTTF electrode materials were obtained by carbonizing HTTF.SEM and TEM were employed to observe the morphological of HTTF and CHTTF,and the structure and composition was analyzed by TG,XRD,Raman and XPS.The electrochemical properties of electrode materials were tested on the electrochemical station.The HTTF synthesized by hydrothermal method has the unique microstructure of sheet,and then the HTTF aggregated into the porous spherical or irregular mass.After carbonization,the CHTTF of irregular mass was obtained.The surface of CTF has some pores and lines which formed by the melting of HTTF.The electrochemical properties were characterized in 2.0 mol L^-1 H₂SO₄ electrolyte.The C_spp of CHTTF was 220.8 F g^-1 at 1 A g^-1 current density and the rate capability was 78.4%of capacitance retention at 10 A g^-1 with an excellent performance.After a long cycle of10000 times at the current density of 10 A g^-1,the capacitance retention rate is as high as101%with excellent cycling stability.,The CTF has great potential in application as the electrode material of supercapacitor.Thiourea formaldehyde resin/PPy hollow spheres composites（TF/PPy）were synthesized by using PPy hollow spheres dispersion as the reaction site for TF.After carbonization,a new type of carbon electrode material based on resin（CTF/PPy）was prepared.Different electrode materials were prepared by adjusting the amount of PPy hollow spheres.Through SEM and TEM analysis,the surface morphology of CTF/PPy was changed and made smooth.By TG,XRD,Raman,XPS and other technical means,it was found that the addition of the PPy hollow spheres changed the chemical structure of the CTF,enhanced the degree of graphitization of CTF/PPy,and changed the binding state of heteroatoms in CTF/PPy,which improved the hydrophilicity of the electrode material and improved more pseudocapacitance for CTF/PPy.The specific capacitance value is226.8 F g^-1 under the current density of 1 A g^-11 and the capacitance retention rate is 67%at 10 A g^-1.After 10000 cycles at the current density of 10 A g^-11 the capacitance retention is up to 120.1%with an excellent cycling stability.Work for supercapacitor,the.CTF is a rare electrode material.MnCO₃ was used as manganese source and compounded with TF to obtain thiourea formaldehyde resin/MnCO₃ composite material（TF/MnCO₃）.The CTF/MnO was obtained by carbonizing the TF/MnCO₃,and the CTF/MnO₂ was prepared by carbonizing the oxide of the pre-carbide of TF/MnCO₃.According to the results of TG,XRD and Raman,Mn was successfully doped into CTF.Electrochemical analysis of CTF/MnO and CTF/MnO₂,the specific capacitance value of CTF/MnO and CTF/MnO₂ is 193.5 F g^-1and 232.5 F g^-1 at the current density of 1 A g^-1,the capacitance retention is 74.9%and73.5%at 10 A g^-1,respectively,the electrodes with excellent cycle stability are suitable for the application of supercapacitors.