research poster hu, davis suli summer 2014
TRANSCRIPT
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