Reduction of Graphene Oxide for Application in Thin-Film

Supercapacitors

Davis Hu1, Ilia Ivanov2*, Mussie Alemseghed2, Michael Hu2

1Maryville College, Maryville, TN 37804 · 2Oak Ridge National Laboratory · *Mentor

ABSTRACT

ACKNOWLEDGMENTSThis work was supported by the Department of Energy Oak

Ridge National Laboratory and Oak Ridge Institute for

Science and Education under the Summer Undergraduate

Laboratory Internship program. I would like to thank my

mentor Ilia Ivanov for his mentorship. I would also like to

thank Mussie Alemseghed for providing GO synthesis.

Lastly, I would like to thank Michael Hu for his eye directing vision for making this project possible.

BACKGROUND

RESEARCH QUESTION EXPERIMENTAL RESULTS AND DATA

MATERIALS/METHODS

• The goal of this project is to develop laser-based

reduction of GO for the design of advanced solid

state capacitors and flexible electronic circuits.

The reduction of GO was done using three lasers

(532, 633 and 785 nm) focused confocally

through a 20x, 50x and 100 x objectives on the

sample of GO deposited on the surface of a

glass slide.

EXPERIMENTAL RESULTS AND DATA

• Graphene Oxide (GO), an oxidized form of

graphene, is a single or multi-layered molecular

sheet synthesized from graphite crystals, have

recently been used in conductive transparent films

and other energy-related applications.

• The production of reduced rGO can be

accomplished by microwave, photo and laser

heating methods.

What is the optimized

conditions for the reduction of

Graphene Oxide using laser?

WHAT IS GO?

Figure 1. Molecular structure of graphene.

Reference: Openstax CNX www.cnx.org

Figure 2. Reduction process of graphite to GO to rGO.

Reference: The University of Turku www.utu.fi

MANAGING SUPPORT

Figure 3. Dispersed GO in alcohol can be printed on

flexible substrates and reduced to generate conductive

and dielectric circuits of the next generation.

• Glass slides were cleaned with alcohol prior to GO

deposition.

• X-Y-Z computer controlled sono-spray deposition

(SonoTek Exactacoat Ultrasonic Coating System) was

used to create 1, 2, 5, 10, 15, and 20 GO layers on the

glass slides

• Raman spectrum of GO is measured as a function of

irradiation time.

• A writable LightScribe supported Verbatim CD-R 52x

was obtained from mentor.

• GO was deposited using sono-spray increasing

number of layers from left to right. Square electrodes

were burned five times to achieve rGO.

• Conductivity is measured using four-point probe.

• Gold/Chrome electrodes were deposited onto quartz

slides containing GO.

• Wires were attached to the gold/chrome electrodes

using silver paste.

• GO is reduced to rGO using laser focused between

electrodes.

• The impedance of GO were measured as a function of

irradiation time.

UV-Visible Spectroscopy•Technique to measure absorption or reflectance in the visible

range.

•Molecules undergo electronic transitions in the regions.

•π or non-bonding electrons absorb energy in the form of UV or

visible light to excite the electrons to higher anti-bonding

molecular orbitals.

Figure 4. A series of glass slides with 1, 2, 5,10,15 and 20

GO layers

Figure 5. Square rGO electrodes on CD

Raman Spectroscopy•Raman spectroscopy is the common method to characterize

rate of reduction of graphene by determining information such

as disorder, edge and grain boundaries, thickness, doping,

strain and thermal conductivity under varying physical

conditions.

•The various conditions are: exposure time (1, 2, 3, 5, 10, 15,

20, 30, 60 min), laser wavelength (532, 633, 785 nm), objective

lens (20x, 50x, 100x), and power (1%, 10%, 100%)

•In graphene, the Stokes phonon energy shift caused by laser

excitation creates two main peaks in Raman spectrum: G (1580

cm-1), a primary in-plane vibrational mode, and 2D (2690 cm-1),

a second-order overtone of a different in-plane vibration, D

(1350 cm-1)

•The reduction of GO can be determined by plotting the ID/IG

Intensity Ratio vs. Time signifying an initial high peak of ratio

intensity followed by decrease in reduction.

Capacitance Using Cyclic Voltammetry•Used a three electrode setup consisting of working, reference and

counter which are glassy carbon, Ag/AgCl, and Platinum

respectively.

Electrochemical Impedance Spectroscopy•Dielectric properties of materials can be measured using

EIS. The measured frequency dependent impedance

response can be modeled using equivalent circuit model and

the capacitance element can be obtained.

CONCLUSIONS

Figure 6. Test structure for measuring kinetics of

GOrGO using impedance and Raman spectroscopy

• GO can be reduced to produce rGO with 532,

633, 785 nm lasers. The best laser for reduction

is at 633 nm.

• Raman D and G peaks are prominent at 532

(green) and 633 nm (red) but not for 785 nm

(purple) which explains that the Raman intensity

depends on the laser wavelength color.

• The maximum capacitance of GO was found to

be 2.70x10-3 F/g at 0.4 volts and 1.74 F/g at 0.7

volts in acetonitrile and NaOH respectively. The

value of the capacitance was calculated at a

range from 0.2 to 0.5 volts/sec and 0.25 to 1.00

volts/sec for acetonitrile and NaOH respectively.

• EIS and equivalent circuit modeling gave the

capacitance value of 7.88240-11 F.

GO in Alcohol Solution Flexible Electronics

GO

rGO

Reference: ScienceRay www.scienceray.com