Chemically-dissected Carbon Nanotubes Functionalized With Organic Moleculars And Their Applications In Supercapacitors

Supercapacitor is next generation energy storage device,which can be charged and discharged quickly,but usually has relatively low energy storage capability when compared with batteries.The application of nanostructured materials with bespoke morphologies and properties to supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability.In particular,carbon based electrode materials are promising to bridge the performance disparity between batteries and capacitors by constructing the energy storage devices,because of their outstanding electrical conductivity.Carbon nanotubes?CNTs?is one of the important carbon-based materials and their structure dependent mechanical and electronic properties.Researchers have been dedicated to improve its performance selectively in certain areas by tailoring its structure to meet specific needs.The length and functionality of the dissected carbon nanotubes?DCNTs?are very important characteristics for specific purposes,and there is no doubt that the work performed in this field has significantly improved researchers ability to manipulate CNTs as well as CNTs solubility,this has enhanced their compatibility in composite materials.In this paper,the DCNTs were modified by?non?-covalent strategies using small electroactive organic molecules as guest molecules.The physical,electrochemical and electrochemical characterization methods were used to test the morphology,structure,composition and electrochemical properties of the material.In addition,the electrode materials with excellent electrochemical performance are rationally matched,and the asymmetrical and symmetrical supercapacitor are designed and assembled to characterize the performance of the capacitor by electrochemical test.The specific research contents are as follows:1.1-hydroxyanthraquinone?HAQ?has been adsorbed onto dissected carbon nanotubes?rDCNTs?with reduced graphene oxide layers through noncovalent interaction.As a result,we realized the functionalization of rDCNTs,which means multi-electron electrochemical active groups have been transplanted to the carbon-based materials to further improve the pseudocapacitance.The surface area of dissected carbon nanotubes is increased by several times compared to Multi-walled carbon nanotubes?MWCNTs?by an oxidative unzipping process while the conductive backbones of MWCNTs are preserved.The special structure and electrical conductivity of the composites guarantee an outstanding super-capacitive performance for the as-prepared material.In the three-electrode configuration,the HAQ-functionalized rDCNTs?HAQ-rDCNTs?electrode exhibits a higher specific capacitance value(as high as 324 F g^-1at 1 A g^-1,two times higher than bare DCNTs)and an ultrahigh rate capability(77.7%capacitance retention at 50 A g^-1)in aqueous electrolyte solutions.For further practical application,a novel asymmetric supercapacitor?ASC?has been assembled by using DCNTs as the positive electrode and HAQ-rDCNTs as the negative electrode in a H₂SO₄ electrolyte.As the result,the device shows an excellent energy storage performance.At a voltage of 1.4 V,the as-fabricated ASC exhibits a high energy density of 12.3 W h kg^-1at a power density of 700 W kg^-1.2.The p-phenylenediamine?PPD?modified chemically dissected carbon nanotubes?DCNTs?composite materials were synthesized by a facile solution processing,which is referred to as DCNTs-PPD.The composite was employed as active supercapacitor electrode materials,the electrochemical properties were studied,and the mechanism how PPD improves the electrochemical performance is investigated systematically.For DCNTs-PPD,the graphene nanoribbons were stacked and cross-linked through PPD molecules.A covalent bond is formed between the amino group in the PPD and the epoxy bond of the DCNTs.The specific capacitance values of DCNTs-PPD is 349 F g^-1at 1 A g^-1.The synthesized material also exhibited an excellent cycling stability as 85.7%retentions after 10000 cycles at current density of 5 A g^-1.The results revealed the role of amine-base organic modifiers in graphene-based supercapacitor materials and validated the DCNTs-PPD as the electrodes of supercapacitor with an excellent electrochemical performance.In addition,we assembled a DCNTs-PPD symmetric capacitor.The test results show that the energy density of the capacitor is as high as 19.1 Wh kg^-1at the power density is800 W kg^-11 in a voltage of 1.6 V.3.Spontaneous grafting of 1-aminoanthraquinone?AAQ?on DCNTs by reduction of the corresponding in situ generated diazonium cations has been successfully achieved and form AAQ-functionalized DCNTs composite electrode material.Electrochemical test results show that the resulting 1-aminoanthraquinone modified electrodes,when tested in aqueous 1 M H₂SO₄,delivered a comparable specific capacitance of 337 F g^-1.The ultrahigh rate capability(71.1%capacitance retention at 20 A g^-1)of AAQ-grafted DCNTs electrodes upon cycling in an acid electrolyte provides indirect evidence for the covalent linkage of AAQ to the carbon substrate.We used composite material as a negative electrode and DCNTs as a positive electrode to assemble an asymmetric capacitor.Due to the good capacitance matching of the anode and cathode materials,the assembled capacitor?DCNTs//DCNTs-AAQ?exhibits excellent energy storage properties.The energy density is up to 19.9 Wh kg^-11 with a power density is 800 W kg^-1.