The Effects of Platinum-Nickel Nanoparticle
Electrocatalyst Morphology on ORR Efficiency
Michael Moon, Enbo Zhu, Professor Yu Huang
UCLA Department of Materials Science and Engineering
Fuel Cells for the Future
The limitations of the fuel cells stand at the cathode catalyst which uses
platinum as its material. The expense and the fuel cell’s lack of efficiency
inhibit the fuel cell from reaching commercialization. By creating a costefficient catalyst that speeds up the oxygen reduction reaction (ORR), we
can improve the fuel cells overall efficiency and commercial viability. To do
this, we will observe the effects of alloying nickel to platinum and
manipulating the morphology of the nanoparticles.
The PEM (Proton Exchange Membrane) Fuel Cell is on a fast track as a new
reliable source of energy to replace traditional sources of energy like the
internal combustion engine. It has a bright future for providing environmentally
friendly energy using renewable fuels. The fuel cell can be used for a variety of
practical applications with a very flexible scalability from cars to powering
industrial facilities.
Pt-Ni Nanoparticle Synthesis
Materials
Tools
1. Prepare a vial for each sample and add the
PVP (polyvinylpyrrolidone) 55000- Capping Agent
for nanoparticle
Citric Acid- Reducing agent
DMF (Dimethylformamide)- Used as a solvent
NaBr (Sodium Bromide)- Influence the formation
of nanoparticle seeds (affects final morphology)
Pt(AcAc)2- Metal precursor to form nanoparticles
Ni(AcAc)2- Metal precursor to form nanoparticles
Sonicator-Used to
homogenize solutions
Centrifuge- Filter and isolate
the nanoparticles for imaging
Transmission Electron
Microscope (TEM)- Imaging
of nanoparticles
necessary substances designated. Prepare
Pt(AcAc)2 and Ni(AcAc)2 solutions and add
specified amount to each well. Sonicate to
homogenize the solution.
Pt(AcAc)2 (left)
Ni(AcAc)2 (right)
Concave Octahedron Morphology
Increases ORR Performance
The amount of NaBr or other substances is observed in a number of
tests on how it affects the morphology and ultimately affecting the
nanoparticle’s catalytic properties. One of the hypotheses for why NaBr
produces these specific morphology is NaBr’s influence on the formation
of seeds in the synthesis process in the oil bath. The introduction of
NaBr eliminate twin defects and produce uniform single crystals.
2. Place each vial in the oil bath for a set time and
3. To clean the sample in order to remove the
temperature. After the allotted time, remove the
vials from the oil bath and proceed to take 1 mL of
each sample and deposit it into
a tube.
PVP and other excess material, add acetone to each
tube and place into the centrifuge for 5-7 minutes.
The acetone is used to precipitate the
nanoparticles, leaving all other excess materials
within the solution
0.188 nm
(200)
0.217 nm
(111)
Oil Bath
4. After centrifugation, use a pipet to drain the
5. On the last cycle once the solution is drained,
excess liquid, leaving only the nanoparticles.
Proceed to add ethanol (to disperse the
nanoparticles) and acetone and place the tube back
in the centrifuge
add ethanol to each tube and sonicate until the
solution is well dispersed. Then proceed to drop the
solution on to a TEM grid and leave it to dry.
High resolution TEM image and a
simulated model
Electrochemical Testing
2
Specific activity (mA/cm )
2.0
2
200
Concave
Commercial Pt/C
100
-2
Current ()
Current density (mA/cm )
0
-4
-100
Concave
Commercial Pt/C
-200
-6
0.2
0
0.4
0.6
0.8
1.0
Potential vs. RHE (V)
1.2
0.0
0.5
1.0
Potential vs. RHE (V)
To test the nanoparticles, we placed them on a three electrode
system containing a counter electrode, reference electrode, and the
working electrode with our Pt-Ni concave octahedron catalyst atop
it. The reference electrode is Ag/AgCl in 3M NaCl. We were able
to receive data on both the electrochemical surface area (cm2) of the
catalyst as well as the kinetic current (mA) to give us the specific
activity of the catalyst. The electrochemical surface area of the
concave octahedron catalyst was lower, but it provided a higher
kinetic current and thus it has a higher specific activity
(left) Calculating and
comparing the kinetic
current (mA) between
the two catalysts
(right) The
electrochemical surface
area is determined by
integrating the hydrogen
adsorption area of the
curve.
1.5
1.0
12.68
0.5
0.0
Commercial Pt/C
Concave
XRD analysis of the surface index shows
the lattice structure of morphology
 Concave octahedron morphology
performed 12 times greater than the
current commercialized Pt catalyst.
 A great amount of corners and edges in
the morphology was produced while
reducing the exposed flat surface area.
 Surface energy is increased at the edges
and corners of structures because they
have extra open bonds that the flat
surface would have bonded to each other.
 The more edges and corners produced,
the more surface energy, resulting in a
higher ORR activity.
Conclusion
A three electrode system used to test the Pt-Ni
nanoparticle electrocatalysts
Our concave octahedron Pt-Ni alloy catalysts performs ORRs at a
significantly higher efficiency compared to commercial PEM fuel
cell cathode catalysts. Further investigations of new morphologies
and other bimetal alloys may progress this efficiency to greater
levels, propelling commercial viability of fuel cells as competitors
and replacements to traditional sources of energy.
Acknowledgements
I would like to thank UCLA and the HSSEAS for their support for the HSSRP as well as Dean Dhir for allowing the program to include housing. A special thanks goes out to my daily lab supervisor
Enbo Zhu for all of his patience in helping me with my project. I would like to thank Professor Yu Huang for allowing me to use her lab. I would like to thank James Che, Harsha Kittur, and William
Herrera for all their hard work they have poured into the program. I would like to thank my RA’s Kington Tse, Lowell Mansilla, and Zoe Xi for all their help and guidance.