Gives an idea about Nanoparticle's background and introduction to Nanoworld. Engineering the shape and thus surface structure of Pt nanocrystals is an effective strategy for optimizing their catalytic activities toward various reactions. However, different protocols are typically used to produce Pt nanocrystals with distinctive shapes, making it difficult to directly compare their catalytic activities owing to the complication of surface contamination. Here we demonstrate that Pt nanocrystals with a variety of shapes, including those enclosed with low- or high-index facets, can be synthesized using the same protocol by simply adjusting the concentration of reducing agent and/or the reaction time.

1. Synthesis of Pt nanocrystals with
different shapes using the same
protocol to optimize their catalytic
activity
Amol Nanduji Jaybhaye

2. Overview
• Background on nanoparticles
• Synthesis and experimentation
• Characterization
• Conclusion and future prospective
2

3. Background on Nanoparticle
• “Nanotechnology is the science of manipulating matter at nanoscale.”
• ‘Nano’ is a Greek word, means Dwarf
• 1nm = 10-9 m i.e. One billionth of a meter
• Every substance regardless of composition exhibits new properties
when the size is reduced to nanoscale.
3N.K. Tolochko NANOSCIENCE AND NANOTECHNOLOGIES - History Of Nanotechnology Encyclopedia of Life Support Systems (EOLSS), 2009, page no 50-60.

4. Things behave differently in Nano-World
• Carbon
Graphite (pencil lead) can be stronger than steel
and six time lighter
• Copper
Highly elastic metal at room temperature
Stretch 50 times its original length without breaking
• Gold
Shiny orange yellow Gold changes its color to
red, brownish black on reducing the size.
Benelmekki, M. Designing Hybrid Nanoparticles; Morgan & Claypool Publishers, 2015.
4

5. Top-down Approach
M. Designing Hybrid Nanoparticles; Morgan & Claypool Publishers, 2015, Chapter 2.Benelmekki, M. Designing Hybrid Nanoparticles; Morgan & Claypool Publishers, 2015, Chapter 2.
Chan,H.-K.;Kwok,P.C.L.ProductionMethodsforNanodrugParticlesUsingtheBottom-up
Bottom-up Approach
5

6. History of Nanotechnology
N.K. Tolochko NANOSCIENCE AND NANOTECHNOLOGIES - History Of Nanotechnology Encyclopedia of Life Support Systems (EOLSS), 2009, page no 50-60. 6

7. Proton Exchange Membrane (PEM) fuel cells
Very attractive for
transportation and
related fields
Clean energy source
in high power density
at low emission
Direct methanol fuel
cells (DMFCs)
Oxygen reduction
reaction (ORR)
Borup, R.; Meyers, J.; Pivovar, B.; Kim, Y. S.; Mukundan, R.; Garland, N.; Myers, D.; Wilson, M.; Garzon, F.; Wood, D.; et al. Scientific Aspects of Polymer Electrolyte Fuel Cell
Durability and Degradation. Chem. Rev. 2007, 107 (10), 3904–3951. 7

8. Oxygen Reduction Reaction (ORR)
• Important reaction in biological respiration, and in energy converting
systems such as fuel cells
• Pt is the most efficient electro-catalyst can accelerate sluggish kinetics that
occur at Cathode of PEM fuel cells
• Platinum (Pt)-
- High cost
- Low reserves in earth’s crust
8Borup, R.; Meyers, J.; Pivovar, B.; Kim, Y. S.; Mukundan, R.; Garland, N.; Myers, D.; Wilson, M.; Garzon, F.; Wood, D.; et al. Scientific Aspects of Polymer Electrolyte Fuel Cell
Durability and Degradation. Chem. Rev. 2007, 107 (10), 3904–3951.

9. Platinum (Pt) Nanoparticles
• Can mitigate Platinum issue in ORR
• Pt nanoparticles have enhanced catalytic activity compare to bulk
form Pt
• Catalytic activities depend on the type of facets exposed on
nanocrystal surface
Mazumder, V.; Lee, Y.; Sun, S. Recent Development of Active Nanoparticle Catalysts for Fuel Cell Reactions. Adv. Funct. Mater. 2010, 20 (8), 1224–1231. 9

10. Platinum (Pt) Nanoparticles (cont.)
• Low index facets :
have low specific surface energy
ex: {100} and {111}
• High index facets : enhanced catalytic activity
high densities of atomic steps, kinks, edges, and can thus
provide more active sites to break chemical bonds
Quan, Z.; Wang, Y.; Fang, J. High-Index Faceted Noble Metal Nanocrystals. Acc. Chem. Res. 2013, 46 (2), 191–202. 10
Hard to compare different facets / nanoparticles as surfaces covered
by different species due to use of different chemicals / protocols

11. What is the Author’s Purpose?
• Facile method for synthesis of Pt nanocrystals with diversified shapes
exposing Low- or High-index facets
• High index facets have more oxygen reduction reaction than low
index facets
Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.
11

12. Experimental Procedure
• Sodium hexachloroplatinate(IV) hexahydrate (Na2PtCl6)
as a precursor
• Glucose as a reductant
• Hexadecyltrimethylammonium bromide (CTAB) as a surfactant
• Oleylamine (OAm) as a solvent, a surfactant, and
a co-reductant
12Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

13. Experimental Procedure (cont.)
Schematic illustration of two different growing pathways that lead to the generation of Pt nanocrystals with
distinctive shapes as a function of reaction time.
13Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

14. So We’ve Synthesized the
Nanoparticles.
Now What?
14

15. So We’ve Synthesized the
Nanoparticles.
Now What?
Characterization
15

16. TEM (Transmission Electron Microscopy)
a) Initial burst of Nucleation for
the formation of Pt
seeds with sizes range 1-4nm
0.25 h
b) Seeds evolved into
Truncated cubes
opposite faces - 6.5 nm
1 h
16Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.
c) Formation of Cuboctahedrons
opposite faces – 8.6 nm
2h
d)Truncated octahedrons
opposite faces – 12.9 nm
3h

17. TEM (Transmission Electron Microscopy)
(cont.)
e) Pt octahedrons with {111}
facets only
average edge length- 18.5 nm
4h
f) Larger Pt octahedrons
average edge length- 21.4 nm
5h
17Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

18. What we get from TEM (Transmission
Electron Microscopy) images?
Shape of Pt nanocrystals is highly depending on the reaction time.
Obtained 4 distinctive shapes or type of facets on the surface by
simply varying reaction time at a fixed glucose concentration.
18Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

19. TEM (Transmission Electron Microscopy)
a) Pt hollow crystals
Absence of glucose
Avg. size- 24.1 nm
b) Mixture of Pt octahedrons(21%)
truncated octahedrons(79%)
Concentration increased to 50mM
19Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.
c) Different morphologies like
truncated cubes, cuboctahedrons,
rods, and tripods
Concentration increased to 133 mM
d) Pt concave cubes
apex to apex – 12.2 nm
High concentration- 167mM

20. TEM (Transmission Electron Microscopy)
(cont.)
e) Smaller concave cubes –
Broaden size distribution and other shapes
200 mM
f) Smaller concave cubes –
Broaden size distribution and other shapes
300 mM
20Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

21. What we get from TEM (Transmission
Electron Microscopy) images?
Shape of Pt nanocrystals is also depending on the
concentration of reductant i.e. Glucose
Obtained different shapes or type of facets on the surface
by simply varying glucose concentration.
21

22. TEM Images of Intermediate products at
different synthesis stages
a) Pt cubes- early stage
5.2 nm avg. edge length
1h
b) Pt cubes- edge length enclosed by {100} facets
increased to 8.1 nm, narrow size distribution
2h
22Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

23. TEM Images of Intermediate products at
different stages (cont.)
c) Cubes to Concave Cubes
Avg. apex to apex 10.1 nm
3h
d) Concave cubes-
Concavity increased- 12.2 nm
4h
23Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

24. HRTEM Images of Pt concave cube (t= 4h)
with FFT pattern
e) Average angle measured - 15.8o
f) Fast Fourier transform (FFT) pattern
24Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.

25. HRTEM of edge region of Concave cube
g) edge region recorded from a concave cube
h) atomic model of the Pt{7 2 0} plane
-contains Multiple steps and
Subsets{410} and {310}
Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt
Nanocrystals with Different Shapes Using the Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction.
Materials Today 2018, 21 (8), 834–844.
25
Average angle measured - 15.8o
Theoretical value - 15.9o

26. cube octahedron concave cubecube octahedron concave cube
Surface effect of different shaped Pt
nanoparticles
26
Histogram of the comparative mass and specific activities at 0.90 V for the as-tested
catalysts.
Qian, J.; Shen, M.; Zhou, S.; Lee, C.-T.; Zhao, M.; Lyu, Z.; Hood, Z. D.; Vara, M.; Gilroy, K. D.; Wang, K.; et al. Synthesis of Pt Nanocrystals with Different Shapes Using the
Same Protocol to Optimize Their Catalytic Activity toward Oxygen Reduction. Materials Today 2018, 21 (8), 834–844.
The specific and mass activity depend strongly on the shape/facet, which
showed a trend in the order sequence of Pt{7 2 0} > Pt{1 1 1} > Pt{1 0 0}.

27. Conclusion
• Simple approach for shape/facet-controlled synthesis of Pt
nanocrystals by manipulating the reduction kinetics.
• Direct comparison of diverse nanoparticles activities towards ORR.
• High-index facets on Pt concave cubes gave more specific activity
compared to low-index facets, octahedrons and cubes.
27

28. Future Prospective
Good example of shape or facets-controlled
synthesis of Pt nanocrystals.
Shed light for development of future
nanocatalysts with optimal specific activities
toward different type of chemical reactions.
Significance of reduction kinetics in controlling
the structure evolution of other metal
nanocrystals.
28
Future Prospective
Good example of shape or facets-controlled
synthesis of Pt nanocrystals.
Shed light for development of future
nanocatalysts with optimal specific activities
toward different type of chemical reactions.
Significance of reduction kinetics in controlling
the structure evolution of other metal
nanocrystals.

29. Thank you all.
29