MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY OF
SCIENCE AND TECNOLOGY
DO CHI LINH
Major:
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Proton exchange membrane fuel cell (PEMFC), a potential
renewable energy source in the near future, has been considerablely
studied in the world. The advantages of the PEMFCs are low
temperature operation, high conversion efficiency, fast startup, low
temperature operation (<100°C), flexible power scalee and
particularly friendly environment. The application of PEMFC
focuses on three main areas: transportation, power supply for
residential areas and power for portable electronic devices.
Platinum is the ideal catalyst material for PEMFC due to its
high catalytic activity for hydrogen oxidation (HOR) and oxygen
reduction (ORR) reactions as well as high stability in low pH
environments at cathode. However, Pt is precious and expensive, so
the use of this material will greatly increase the cost of PEMFC. This
is one of the major challenges that limit the commercialization of
PEMFCs in the world.
To reduce the Pt metallic catalyst content, development of
nanotechnology has played an important role with research of
dispersing Pt metallic particles on carbon supports. To disperse
catalyst nano6particles means that the catalyst surface area is
increased. In some reports, this area may reach to approcimately 120
m
2
/g. As a result, the activity of the catalyst material has been
significantly improved and Pt metallic loading might dropped to 0.4
mg/cm
2
while PEMFC properties change insignificantly.
Using Pt alloy catalysts with cheaper metals as electrode
material is another effective approche for reducing PEMFC costs.
For anodic catalysts, many Pt alloys with alloying metals such as Ru,
W, Sn, Pd… have been studied. These studies have shown that using
catalyst alloys may improve catalytic activity for hydrogen oxidation
reaction (HOR) and CO poisoning in PEMFC. For cathode ctalysts,
Pt6M catalyst alloys (with M transition metals such as Mn, Cr, Fe,
Co and Ni) are the most widely studied due to activity for oxygen
reduction reaction (ORR) higher than pure Pt. Alloying catalysts
improve ORR activity towards reducing oxygen by direct 46electron
reaction withou H
2
O
2
intermediate stage therefore catalytic activity
of these alloys may be higher 365 times compared to pure Pt / C
catalysts.
In Vietnam, research on PEMFC fuel cells has not
intensively been considered and there are few research groups being
studying on direct methanol fuel cell. With desire to develop PEMFC
area using direct hydrogen fuel, research on catalytic materials is
essential. Therefore, the topic of the thesis was chosen as: “Synthesis
and characterization of carbon supported Pt and Pt alloy
nanoparticles as electrocatalysts material for proton exchange
membrane fuel cell”
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6 Research and development of Pt/C and Pt6M/C alloys high
performence catalysts to apply in proton exchange membrane fuel
cells using direct hydrogen fuel.
6 Research and development of single PEM fuel cell having high
power density with active area of 5cm
2
.
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6 Introdution of fuel cell and studies on Pt catalysts and Pt alloy
catalysts in PEMFC.
6 Research on synthesis of catalytic materials Pt/C 20% wt. by
electroless deposition method and evaluating to influence of
experimental parameters such as pH, temperature... in the synthesis
process on the properties of catalyst Pt / C 20%wt.
6 To optimum process for synthesis of Pt/C highly active catalysts as
electrode materials in PEMFC.
6 Research on synthesis of Pt6M/C alloy catalyst 20%wt. (M = Ni,
Co and Fe) by electroless deposition method and characterization of
alloy catalysts to select a suitable alloy catalyst for ORR at cathode
in PEMFC.
6 Researching, designing, and fabricating components of a single
PEM fuel cell with active area of 5cm
2
and study on operating
conditions for single fuel cell.
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6 Brief introduction on history, configuration, operation principle and
application of PEMFC.
6 Describe the mechanisms and kinetics of hydrogen oxidation
reaction and oxygen reduction reaction taking place on Pt / C
catalysts in PEMFC
6 Introduction of history, research and development of catalytic
materials serving as anode and cathode in PEMFC.
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Pt/C catalyst with metallic content of 20%wt. is synthesized
by electroless deposition using ethylene glycol and NaBH
4
assisted
ethylene glycol. In ethylene glycol preparation, Pt/C catalysts were
synthesized at temperatures of 80°C and 140°C. In addition, the
catalysts were synthesized in a mixture of ethylene glycol: water by
ratios (EG: W) of 9:1, 7:1, 5:1, and 3:1 (in unit volume). In NaBH
4
assisted ethylene glycol method, catalytic samples are synthesized in
mixture solvents with varying pH values of 10; 7; 4 and 2
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In characterization of catalytic materials and MEA
electrodes, catalytic particles were prepared into catalytic inks
including Pt/C and Pt
3
M/C catalyst particles with metallic content of
20%wt into a mixture solvent. Catalyst composition includes
metallic catalyst of 5mg, absolute ethanol of 4 ml, and Nafion
solution 10% of 25 Gl.
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The MEA electrodes with a nafion membrane sandwiched
between two symmetry diffusion layers coated with catalyst ink were
prepared hot6pressing method. Catalysts were prepared by brushing
catalyst ink onto a gas diffusion carbon paper with active area of 5
cm
2
.
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Transmission Electron Microscopy TEM is used to evaluate
the size and distribution of metallic catalyst particles while X6ray
diffraction is used to evaluate the structure and alloying degree of
Pt6M/C catalysts. Energy6Dispersive X6Ray Spectroscopy (EDX)
were used to determine the purity of the synthesized Pt/C catalysts.
2.4.2.1. Cyclic Voltammetry (CV)
The electrochemical sample is holded into a Teflon mold
with a working area of 1 cm
2
. The measurements were conducted in
a three electrode cell with counter electrode as platinum and the
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