skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Attention:

The DOI auto-population feature in the Public Access Repository (PAR) will be unavailable from 4:00 PM ET on Tuesday, July 8 until 4:00 PM ET on Wednesday, July 9 due to scheduled maintenance. We apologize for the inconvenience caused.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • ZIF-67-derived edge-oriented graphene clusters coupled with carbon nanotubes containing encapsulated Co nanoparticles for high-frequency electrochemical capacitors
Title: ZIF-67-derived edge-oriented graphene clusters coupled with carbon nanotubes containing encapsulated Co nanoparticles for high-frequency electrochemical capacitors
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.  more » « less
Award ID(s):
1611060 1820098
PAR ID:
10114168
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Sustainable Energy & Fuels
ISSN:
2398-4902
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, Small)
    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. 
    more » « less
  2. ; ; ; ; ; ; (, Batteries & Supercaps)
    Abstract An ultra‐fast electrochemical capacitor (EC) designed for efficient ripple current smoothing was fabricated using vertically oriented MoS2(VOM) nanoflakes deposited on freestanding carbonized cellulose (CC) sheets as electrodes. The daily used cellulose tissue sheets were transformed into electrode scaffolds through a rapid pyrolysis process within a preheated furnace, on which VOM nanoflakes were formed in a conventional hydrothermal process. With these ~10 μm thick VOM‐CC electrodes, ultrafast ECs with tunable frequency response and specific capacitance density were fabricated. The ECs with a cell‐level areal capacitance density of 0.8 mF/cm2at 120 Hz were demonstrated for ripple current filtering from 60 Hz to 60 kHz. At a lower frequency response level, EC cell with a large capacitance density of 4.8 mF/cm2was also demonstrated. With the facile and easily scaled up process to producing the nanostructured electrode, the miniaturized VOM‐CC based ECs have the potential to substitute the bulky aluminum electrolytic capacitors for current smoothing and pulse power applications. 
    more » « less
  3. ; ; ; ; (, MRS Advances)
    ABSTRACT Compact-size kilohertz (kHz) AC-supercapacitors are being pursued for ripple current filtering and pulsed energy storage. However, their development is limited by a small areal capacitance density due to very thin electrode used for meeting frequency requirement. In our work, crosslinked carbon nanofiber aerogel (CCNFA) was investigated as freestanding electrode for kHz AC-supercapacitors with an areal capacitance density as large as 4.5 mF cm -2 at 120 Hz, 5-10 times larger than most reports. The CCNFA was obtained in a rapid plasma carbonization process of bacterial cellulose. The fabrication route adopted here is simple and straightforward, and the produced CCNFA electrode was found to be very suitable for high-frequency AC-supercapacitors. The operating voltage range of CCNFA based AC-supercapacitors can be expanded to 3 V by utilizing an organic electrolyte. In addition to AC-Supercapacitor performance, the morphology and material properties of bacterial cellulose aerogel and CCNFA were also reported. 
    more » « less
  4. ; ; ; ; (, Materials)
    There is strong interest in developing high-frequency (HF) supercapacitors or electrochemical capacitors (ECs), which can work at the hundreds to kilo hertz range for line-frequency alternating current (AC) filtering in the substitution of bulky aluminum electrolytic capacitors, with broad applications in the power and electronic fields. Although great progress has been achieved in the studies of electrode materials for ECs, most of them are not suitable to work in this high frequency range because of the slow electrochemical processes involved. Edge-oriented vertical graphene (VG) networks on 3D scaffolds have a unique structure that offers straightforward pore configuration, reasonable surface area, and high electronic conductivity, thus allowing the fabrication of HF-ECs. Comparatively, highly conductive freestanding cross-linked carbon nanofibers (CCNFs), derived from bacterial cellulose in a rapid plasma pyrolysis process, can also provide a large surface area but free of rate-limiting micropores, and are another good candidate for HF-ECs. In this mini review, advances in these fields are summarized, with emphasis on our recent contributions in the study of these materials and their electrochemical properties including preliminary demonstrations of HF-ECs for AC line filtering and pulse power storage applications. 
    more » « less
  5. ; ; ; ; (, Energy Advances)
    Electrochemical double-layer capacitors (EDLCs) provide high power density and long cycle life energy storage. This work examines the use of inexpensive, raw coal char as an electrode material for supercapacitors. The effect of electrolyte composition on the performance of coal char supercapacitors is explored for the first time to determine the relative contributions of double-layer capacitance vs. faradaic reactions on total charge storage. Six electrolytes are examined with coal char electrodes, including: four aqueous electrolytes (0.5 M H 2 SO 4 , 6 M KOH, 0.5 M Na 2 SO 4 , 4 M LiNO 3 ); a water-in-salt electrolyte using 13 m NaClO 4 ; and an ionic liquid electrolyte (1-butyl-3-methylimidazolium tetrafluoroborate in acetonitrile). Voltage range, specific capacitance, electrochemical impedance, and charge–discharge characteristics of the coal char in the different electrolytes are characterized. The results indicate that neutral aqueous, water-in-salt, and ionic liquid electrolytes present a charging/discharging process approaching ideal EDLC behavior. The study provides insight into the optimal electrolyte composition for use with coal char electrodes and contributes to the current understanding of electrode-electrolyte interactions in carbon supercapacitors. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email