Abstract
Covalent organic frameworks (COFs) constitute a family of crystalline porous polymers that are being studied for electrochemical energy storage. However, their low electrical conductivity and poor processability have largely limited their electrochemical performances and practical applications. Here, we develop an interfacial synthesis method to grow few-layered 2D redox-active COFs (DAAQ-TFP COF) on the surface of carboxylated carbon nanotubes (c-CNTs) in order to fabricate core-shell c-CNT@COF nanofibers, for which the thickness and the morphology of the COF nanolayers can be finely controlled. When using the c-CNT@COFs as electrode material, the tailored nanostructure with high electrical conductivity allows efficient electron transfer, while the few-layered structure of the COF promotes fast electrolyte ion diffusion in the near-surface region, which results in an efficient utilization of the redox active sites in COF. More significantly, c-CNT@COFs with nanofibrous structure show good processability and can be assembled into freestanding and flexible nanopapers with the assistance of Cladophora cellulose. Given the good electrochemical performance and excellent flexibility, the nanopaper electrodes are assembled into flexible hybrid capacitors, showing high areal capacitance and extremely long lifetime. This study provides a new pathway for the development of next generation sustainable and flexible energy storage devices based on COFs and cellulose materials.
Highlights
Covalent organic frameworks (COFs) are a new family of crystalline porous organic polymers constructed by covalently linking organic monomers in a periodic manner [1e8]
The high resolution transmission electron microscope (TEM) image shows the stacking of COF layers with interlayer spacing of ~0.35 nm (Fig. S9), which is agreement with the d spacing of the 001 planes of COF. These results demonstrate that the composition and morphology of the carboxylated carbon nanotubes (c-CNTs)@COF nanocomposites can be finely controlled at the nanoscale by the interfacial synthesis method, which allows for a fundamental understanding of their structure-property relationships and opens up for regulation of their performances in electrochemical energy storage
Freestanding and flexible nanopaper electrodes based on redox active COFs have been successfully fabricated by a bottom-up nanoengineering approach, which involves interfacial synthesis of c-CNT@COF nanofibers and interweaving of the hybrid nanofibers with nanocellulose and CNTs
Summary
Covalent organic frameworks (COFs) are a new family of crystalline porous organic polymers constructed by covalently linking organic monomers in a periodic manner [1e8]. Owing to their unique properties of long-range ordered nanopores and frameworks, high specific surface areas, and good physicochemical stability, COFs have been extensively studied for applications in gas storage and separation [9,10], catalysis [11e13], drug delivery [14], and sensing [15,16]. The difficulty in processing COF crystals significantly limits their applications in electrochemical energy storage, especially for the uses in flexible devices. It would be very desirable to develop new strategies to design highly conductive, accessible and processable COFs or COF-based nanocomposites for the design of highperformance and flexible energy storage devices
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
