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There is a strong interest in increasing the frequency response of electrochemical capacitors (ECs) from typically less than 1 Hz to the hundreds or the kilo Hz range, so that such high-frequency ECs (HF-ECs) could replace conventional capacitors for AC line-frequency filtering and other capacitor applications. The development of such HF-ECs is hindered by their typically low capacitance density and operation voltage. Herein, by treating ZIF-67 particulate films in CH 4 /H 2 plasma, edge-oriented graphene (EOG) formed around the carbonized ZIF-67 particulate skeleton, and this EOG was coupled with carbon nanotubes (CNTs) that were grown with the aid of Co catalyst nanoparticles, which were generated by reducing the Co 2+ ions associated with ZIF in the plasma. Used as electrodes, these EOG/CNT/carbonized ZIF-67 composites exhibited a large electrode areal capacitance of 1.0 mF cm −2 and an excellent frequency response of −84° phase angle at 120 Hz in aqueous electrolyte cells, whereas values of 0.67 mF cm −2 and −78° for the electrode areal capacitance and the phase angle at 120 Hz, respectively, were obtained in organic electrolyte cells with the operation voltage of 2.5 V. Using three pairs of electrodes stacked together, a single integrated cell operating at 7.5 V and having a characteristic frequency of ∼3.8 kHz at −45° phase angle, was demonstrated. These results suggest the potential to use this EOG/CNT/carbonized ZIF-67 composite structure for developing HF-ECs.
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Carbon Nanostructures Derived from In Situ Grown ZIF Nanocages within Bacterial Cellulose for AC‐Filtering Electrochemical Capacitors
Abstract Electrochemical capacitors (ECs) offer superior specific capacitance for energy storage compared to traditional electrolytic capacitors but face limitations in alternating current (AC) filtering due to the need for balancing fast response and high capacitance. This study addresses these challenges by developing a freestanding nanostructured carbon electrode, derived from the rapid carbonization of bacterial cellulose (BC) embedded with zeolitic imidazolate framework 8 (ZIF‐8) and in situ formed carbon nanotubes (CNTs). The electrode exhibits an exceptionally low area resistance of 9.8 mΩ cm2and a high specific capacitance of 2.1 mF cm−2at 120 Hz, maintaining performance even at high frequencies. Stacking these electrodes enhances the capacitance to 5.3 mF cm−2, with the phase angle degrading to −74.4° at 120 Hz; however, they retain a phase angle below −45° up to ≈50 kHz, demonstrating excellent high‐frequency performance. Furthermore, connecting three aqueous units in series as an integrated cell or utilizing organic electrolytes extends the voltage window to 2.4 V, enhancing their suitability for high‐voltage applications. Ripple voltage analysis under various loads and frequencies indicates effective filtering capabilities, highlighting the potential of these nanostructured ECs for next‐generation electronic applications.
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- Award ID(s):
- 2122921
- PAR ID:
- 10571515
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small
- Volume:
- 21
- Issue:
- 5
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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