TY - JOUR
T1 - Experimental and theoretical investigations of covalent functionalization of 1D/2D carbon-based buckypaper via aryl diazonium chemistry for high-performance energy storage
AU - Juang, Ruei Hung
AU - Guo, Jhao Sian
AU - Huang, Yi Jung
AU - Chen, I. Wen Peter
N1 - Funding Information:
This study was supported by grants from MOST , Taiwan ( MOST 109-2628-M-143- 001-MY3 ).
Funding Information:
To further expand the application of the CF reaction to carbon-based materials, the 1D CNTs buckypaper was studied. Fig. 4b and c shows the SEM image of the fracture surface of the pristine CNTs and CF-CNTs buckypaper, respectively. The red rectangle region of Fig. 4c shows that the individual CNTs of the CF-CNTs buckypaper was bundled and had less pulling length, indicating the successful cross-linking of the CNTs via diazonium chemistry. This phenomenon was also supported by Wan et al. [31] The effect of the electrical conductivity of the CNTs on the CF times was discussed. For a reaction time of 12 min, the electrical conductivity of the CF-CNTs buckypaper was significantly enhanced and reached 82,100 S/m, as shown in Fig. 4d. However, when the functionalization time was over 12 min, the electrical conductivity of the CF-CNTs buckypapers was rapidly decreased. Besides, we also synthesized the 2-methoxy-benzene-diazonium compound to functionalize CNTs. Fig. S4 shows that the electrical conductivity of 2-methoxy-benzene-diazonium functionalized CNTs only reached 34,200 S/m, indicating no efficient conducting pathway formation between each CNT. To unveil the effect of the functionalization time vs electrical conductivity of the CF-CNTs buckypaper, Raman measurements were carried out. Fig. 4e shows that the ID/IG ratios of the CF-CNTs buckypapers are nearly the same within the functionalization time of less than 12 min, indicating only limited biphenyl molecules cross-linking to individual CNT and no significant damage of the CNT surface during the CF reaction. Therefore, the electrical conductivity pathway of intertubes can be greatly increased via effective cross-linking functionalization. However, when the functionalization time is over 12 min, Fig. 4e shows a higher ID/IG ratio of the CF-CNTs buckypaper, which means that too many defect sites were generated on the CNT surfaces that caused the electrical conductivity to become lower (Fig. 4d). To explicitly understand the biphenyl molecules cross-linking intertubes, we studied the effect of temperature on the buckypapers. Fig. 4f shows the electrical conductivity of the CF-CNTs12min buckypaper under an Ar atmosphere at different calcination temperatures. When the calcination temperatures are from 150 to 250 °C (Fig. 4f orange zone), the electrical conductivity of the CF-CNTs12min buckypaper changes from 82,100 S/m to 39,000 S/m; however, the pristine CNTs buckypaper (Fig. 4f) only changes from 17,000 S/m to 15,000 S/m. But the pristine CNTs and CF-CNTs12min buckypaper show very limited weight loss between 150 and 250 °C (Fig. S5). Hence, the electrical conductivity of the CF-CNTs12min buckypaper shows a significant decrease, indicating that the intertubes linked aryl molecules (i.e., biphenyl molecules) were decomposed and reduced the charge transport pathways of the CF-CNTs12min buckypaper. Hirsch et al. reported that the aryl molecule decomposition temperature started from 120 °C; therefore, the decomposition temperature of functionalized biphenyl molecules of the CF-CNTs12min is in agreement with the reported literature [32]. While increasing the calcination temperature, the electrical conductivity of the CF-CNTs12min buckypaper further decreases due to the decomposition of the carbons and aryl molecules (Fig. 4f Indian red zone) on the CF-CNTs12min buckypaper. Hence, by tuning the functionalization time of the 2,2′-dimethoxybiphenyl-4,4′-bis(diazonium) zinc tetrachloride molecule, buckypapers can be successfully crosslinked with individual CNTs and the electrical conductivity of the CF-CNTs buckypaper can be significantly enhanced.This study was supported by grants from MOST, Taiwan (MOST 109-2628-M-143- 001-MY3).
Publisher Copyright:
© 2023 Elsevier Ltd
PY - 2023/3/5
Y1 - 2023/3/5
N2 - Efforts to fabricate high-conducting and high-strength free-standing graphene/carbon nanotube (CNT) buckypaper through room-temperature functionalization have been frustrated by the defective surface of the graphene and CNTs. In this study, high-quality graphene sheets were prepared via an amino-assisted liquid phase exfoliation method and used to integrate with CNTs to form free-standing flexible graphene/CNTs buckypaper. After that, individual graphene and CNT of the graphene/CNTs buckypaper were linked via diazonium chemistry to generate covalent bonds. By tuning functionalization time, the functionalized graphene/CNTs buckypaper exhibits an electrical conductivity of 87,500 S/m and a Young's modulus of 22.3 GPa, which are 6 and 10 times higher, respectively, than unfunctionalized graphene/CNTs buckypaper. Density functional theory calculations demonstrate that charge transfer rate (Ket) of the aryl linker bonded moiety configuration via covalent functionalization is an order faster than without the aryl linker bonded moiety configuration. Unprecedently, the capacitance of the functionalized graphene/CNTs buckypaper is 359.6 mF/cm3 at a scan rate of 1 mV/s with no capacitance change after 10,000 cycles of testing. This work sheds the light of the value of molecular engineering in the design of novel composite for flexible electronics, energy storage and provides important insights into the understanding of basic principles of covalent functionalization of graphene/CNTs.
AB - Efforts to fabricate high-conducting and high-strength free-standing graphene/carbon nanotube (CNT) buckypaper through room-temperature functionalization have been frustrated by the defective surface of the graphene and CNTs. In this study, high-quality graphene sheets were prepared via an amino-assisted liquid phase exfoliation method and used to integrate with CNTs to form free-standing flexible graphene/CNTs buckypaper. After that, individual graphene and CNT of the graphene/CNTs buckypaper were linked via diazonium chemistry to generate covalent bonds. By tuning functionalization time, the functionalized graphene/CNTs buckypaper exhibits an electrical conductivity of 87,500 S/m and a Young's modulus of 22.3 GPa, which are 6 and 10 times higher, respectively, than unfunctionalized graphene/CNTs buckypaper. Density functional theory calculations demonstrate that charge transfer rate (Ket) of the aryl linker bonded moiety configuration via covalent functionalization is an order faster than without the aryl linker bonded moiety configuration. Unprecedently, the capacitance of the functionalized graphene/CNTs buckypaper is 359.6 mF/cm3 at a scan rate of 1 mV/s with no capacitance change after 10,000 cycles of testing. This work sheds the light of the value of molecular engineering in the design of novel composite for flexible electronics, energy storage and provides important insights into the understanding of basic principles of covalent functionalization of graphene/CNTs.
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U2 - 10.1016/j.carbon.2023.01.051
DO - 10.1016/j.carbon.2023.01.051
M3 - Article
AN - SCOPUS:85147103259
SN - 0008-6223
VL - 205
SP - 402
EP - 410
JO - Carbon
JF - Carbon
ER -