| The rapid development in energy storage system increases the urgent to explore electrode materials with higher specific capacitance and higher stability.Conductive polymer as the pseudocapacitance materials are most promising materials due to its low-cost,easy-preparation,facile modification,light weight as well as internal flexibility.However,there are still some defects including low capacity,low energy density,poor cycling life in conducting-polymer-based supercapacitors.It has been reported that recombination of the conductive polymer with other materials can effectively improve the specific capacitance and stability of the compositions.However,the cumbersome procedure and the need of some special instruments indicate the design and synthesis of conductive polymers with higher specific capacitance.Aiming for the design and synthesis of the electrode materials with improved specific capacitance,several donor-acceptor-donor conjugated units and polymers were synthesized by chemically modification of the building blocks.The corresponding significant results are listed as follows.1.4-Methoxyphenene was introduced to thieo[3,4-b]pyrazine(TPZ)building block to get a new building block as the acceptor(A).By coupling with donor units(D)including thiophene,3-methythiophene,3-methoxythiophene,and 3,4-ethylendioxythiophene,four novel D-A conjugated monomers including MPTTPZ,MPMTTPZ,MPMOTTTPZ and MPETTPZ were successfully synthesized,respectively.The corresponding conjugated polymer PMPTTPZ,PMPMTTPZ,PMPMOTTTPZ and PMPETTPZ were obtained facilely by electropolymerization with high thermal stability.Electrochemical tests demonstrated high specific capacitance of 167 F g-1for polymer PMPTTPZ at the current density of 1.0 A g-1,and high capacitance retention of 98.0%at high current density of 30.0 A g-1.Type III supercapacitor assembled by the polymer PMPTTPZ has a maximium energy density of 6.7Wh kg-1.The above results show that improved specific capacitance of the electrode materials and increased energy density of the supercapacitors can be realized by facially structural modification followed by electropolymerization.2.Thienyl was introduced into the TPZ building block.By coupling with thiophene,3-methylthiophene,3-methylmethoxythiophene,3,4-subethyldoxythiophene,we synthesized four D-A conjugated monomers including TTTPZ,TMTTPZ,TMOTTPZ and TETTPZ,respectively.The corresponding electropolymerized polymers showed high thermal stability,high specific capacitance of 200 F g-1of PTTTPZ at the current density of 1.0 A g-1,high capacitance retention of 79.0%after 2000 consecutive charge-discharge cycling at the current density of 5.0 A g-1.High energy density of 8.2 Wh kg-1of the Type III supercapacitor assembled by the polymer PTTTPZ was also concluded.3.Furan was introduced to TPZ building block to get a new acceptor unit.Then,two novel reduced band-gap donor-acceptor conjugated monomer MFMOTPZ and MFMTTPZ were synthesized by Still coupling with 3-methyl thiophene and 3-methoxythiophene.The corresponding conjugated polymer,PMFMOTPZ and PMFMTTPZ,can be obtained facilely by electrochemical polymerization.High specific capacitance of 678 F g-1and 319 F g-1were obtained for polymer PMFMOTPZ and PMFMTTPZ,respectively,at the current density of1.0 A g-1.The specific capacitance of 678 F-1may be among the peak values reported on conducting polymer-based electrodes.Furthermore,type III supercapacitors based on the conjugated polymer had a maximum energy density of 22.4 Wh kg-1and 7.9 Wh kg-1,respectively,with the maximum power density of 16.5 Wh kg-1.4.Four novel donor-acceptor conjugated monomers including TTQ,TMTQ,TMOTQ and TETQ,were synthesized by using thienyl-substituted quinoxaline building block as the acceptor coupled with thiophene,3-methyl thiophene,3-methoxyl thiophene,3,4-ethylenedioxyxythiophene,respectively.The corresponding polymer were obtained by electropolymerization and systematically characterized.High specific of 177 F g-1at the current density of 1.0 A g-1,high capacitance retention of 96.0%after 1000 GCD were concluded from the tests of the polymer PTMTQ.High energy density of 4.2 Wh kg-1of the Type III supercapacitor assembled by the polymer was also concluded.5.To compare the effect of the same substituents on the different building block,the4-methoxybenzene was once again introduced to the quinoxaline building block.Four donor-acceptor conjugated monomers including MPTQ,MPMTQ,MPMOTQ and MPETQ were synthesized.The corresponding polymer were obtained by electrochemical polymerization.High specific capacitance of 237 F g-1at the current density of 1.0 A g-1,high capacitance retention of 95.8%at the current density of 30.0 A g-1were demonstrated from the tests of polymer PMPMTQ.High energy density of 10.5 Wh kg-1of the Type III supercapacitor assembled by the polymer was also concluded.In conclusion,eighteen donor-acceptor conjugated monomers and the corresponding conjugated polymers have been successfully synthesized.These conjugated polymers were used as pseudocapacitance electrodes materials for the first time to investigate the relationship between the conjugated structure and their capacitance,which extend available application for conjugated polymer,and provide a useful reference for the design and synthesis of conjugated polymers with high performance. |
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