Fast Response, vertically oriented graphene nanosheet electric double layer capacitors synthesized from C(2)H(2).

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Vertically oriented graphene nanosheets are promising electrode materials for energy storage devices.
• Radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) is a key technique for graphene synthesis.

Purpose of the Study:

• To investigate the growth and electrical characteristics of vertically oriented graphene nanosheets.
• To evaluate their performance as electrodes in symmetric electric double layer capacitors (EDLCs).

Main Methods:

• Graphene nanosheets were grown using RF-PECVD with C2H2 feedstock on nickel substrates.
• Electrical characteristics were measured using Raman spectroscopy and AC specific capacitance.
• Performance in EDLC devices was assessed, including frequency response and equivalent series resistance.

Main Results:

• C2H2-grown films showed a 2.7x faster growth rate and higher specific capacitance than CH4 films.
• Specific capacitance increased linearly with growth temperature, reaching 265 μF/cm² at 850 °C.
• Devices exhibited ultrafast frequency response (>20 kHz at -45° phase angle).
• Higher growth temperatures (≥800 °C) led to increased surface area and defect density, boosting capacitance but slightly reducing frequency response.
• Low equivalent series resistance (0.07–0.08 Ω) was attributed to carbon incorporation into the Ni substrate.

Conclusions:

• Optimizing growth temperature is crucial for balancing capacitance and frequency response in graphene-based EDLCs.
• Vertically oriented graphene nanosheets grown from C2H2 offer a viable pathway for high-performance energy storage.
• Carbon incorporation into nickel substrates contributes to low equivalent series resistance in the fabricated devices.