Cy 241-assignment-3

Recent Research
Vihari Piratla(B10025)

Ru–Pt core–shell nano-particle
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This section constitutes the summary of [1].
Scientists at the U.S. Department of Energy's (DOE) Brookhaven National
Laboratory -- in research published online September 18, 2013 in the
journal Nature Communications -have created a high -performing
nanocatalyst that solves to a good extent the problems of high cost/rarity of
Pt and poisoning of Pt catalyst upon exposure to CO.
The novel core--shell structure -- ruthenium coated with platinum -- resists
damage from carbon monoxide and also reduces the Pt consumption by
98%.
It was observed that loss of ruthenium on start/shutdown is because of
defect mediated interlayer diffusion and can be avoided by eliminating
lattice defects from ruthenium particles before adding Pt.

Figure 1 shows the effectiveness of various bimetallic structure with respect to
temperature and also observe the comparison with Pt, which does not trigger
into action until 170 degrees. In conclusion this method claims a new nanoperfect Ru@Pt structure that is CO poisoning tolerant and uses 98% less
platinum, they also claim that the manufacturing process is effortless and
scalable and function just as well as platinum at room temperature.

Facile, scalable synthesis of edge halogenated graphene
nanoplatelets as efficient metal-free nanocatalyst.
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This section summarises [2].
This paper published in June 2013, proposes edge halogenated graphene
nano-platelets as a replacement for Pt crystals and also claims that this
replacement has good tolerance towards methanol crossover/CO
poisoning effects and long term cycle stability.
It is also implied that the catalyst in itself is much cheaper because of easy
synthesis and also pervasive nature of primary elements.
In conclusion, a metal--free, easy to synthesise and easily available
catalyst was developed and tested to be better than Pt/C and more robust
than Pt/C. Though the authors state that they have to further optimise the
nano-catalyst, the scope of commercialisation is very high.

continued (Manufacturing difficulties)
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Quantum mechanics calculations revealed that the electron
accepting/donating ability of the heteroatom dopants created net
positive/negative charges on adjacent carbon atoms in graphitic lattice to
facilitate the oxygen reduction process.
Thus, both the vertically- aligned nitrogen- doped carbon nanotubes (VANCNTs) and nitrogen- doped graphene (N-graphene) catalyzed an efficient
four- electron ORR process with a higher electrocatalytic activity and better
operation stability than the commercially available Pt/C-based
electrocatalyst (Pt: 20 wt%, Vulcan XC-72R).
But the manufacturing process stood as an impediment, classical CVD
methods are not scalable.
Proposed a catalyst which can be easily synthesised and scalable.

continued(details of manufacturing)
Ball milling of graphite with halogen produces edge halogenated nanoplatelets
of Graphene(XGnPs).

continued (Durability tests and efficacy tests)
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In a test of durability, electrodes coated with XGnP's maintained 85.6 to
87.4 percent of their initial current after 10,000 cycles while platinum
electrodes maintained only 62.5 percent.
The performance of graphene based catalysts was unaffected with
induction of CO impurity with Hydrogen fuel.
Also in comparison with the Pt/C commercially available catalyst: a
cathode coated with iodine -edged nanoplatelets performed best. A
cathode coated with bromin e-edged nanoparticles generated 7 percent
less current than the commercial cathode coated with platinum, the chlorin
e-edged nanoplatelets 40 percent less.

Nano-catalyst based on carbon-nanotubes
graphene complexes
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This section summarises [3].
For the study, the Stanford team used multi-walled carbon nanotubes
consisting of two or three concentric tubes nested together.
The group showed that shredding the outer wall, while leaving the inner
walls intact, enhances catalytic activity in nanotubes, yet does not interfere
with their ability to conduct electricity.
A typical carbon nanotube has few defects, but defects are actually
important to promote the formation of catalytic sites and to render the
nanotube very active for catalytic reactions.
This paper also obviates some of the misconceptions and states that metal
defects in the catalyst increases catalytic capabilities and hence should not
be ignored.

continued(depiction)
Authors claim that though the outer wall is
unzipped the conductivity remains intact
because of the inner wall and hence can
help in charge mobility.
This nano catalyst has performance
commensurate with Pt/C.
This figure also depicts iron and nitrogen
impurities which contribute in allaying the
capability.

Summary
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We are evidencing a revolution in the research of nano catalysts with the
advent of Nano-science and nano imaging techniques like STEM.
Nanocatalysts have a larger scope in catalysis because of
○ increased surface area,
○ possibility of producing defect free and hence very conductive.
Also because of the enhanced imaging techniques, the pioneers are able
to observe the factors that influence the active sites and catalytic abilities
and thus leading to better catalysts like NickelPhosphide.

Summary(continued)
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We have seen metal--free catalysts that can function better or just as well
as Pt/C and also have seen modification to Pt catalysts to nano-catalysts
to improve the robustness and alleviate cost.
These fuel cells can be much cheaper because of the reduced catalyst
cost which constitutes 40% and also reduced cost of hydrogen fuel
because of the relaxed constraint of CO poisoning.
The day when HFC's replace IC engines is near and can be one stop
solution for depriving sources of oils and green-house gases.
Seems like, only possible piece of puzzle that needs to be solved is
efficient(Volume/weight ratio) and safe storage of Hydrogen.

References
1.

Yu-Chi Hsieh, Yu Zhang, Dong Su, Vyacheslav Volkov, Rui Si, Lijun Wu, Yimei Zhu, Wei An, Ping Liu, Ping He, Siyu Ye,
Radoslav R. Adzic & Jia X Wang (2013) Ordered bilayer ruthenium–platinum core-shell nanoparticles as carbon monoxidetolerant fuel cell catalysts. Nature Communications 4, Article number: 2466 doi: 10.1038/ncomms3466

2.

Jeon, I., Choi, H., Choi, M., Seo, J., Jung, S., Kim, M., Zhang, S., Zhang, L., Xia, Z., Dai, L. and Others. 2013. Facile,
scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal- free eletrocatalysts for oxygen reduction
reaction.
Li, Y., Zhou, W., Wang, H., Xie, L., Liang, Y., Wei, F., Idrobo, J., Pennycook, S. and Dai, H. 2012. An oxygen reduction
electrocatalyst based on carbon nanotube-graphene complexes. Nature nanotechnology, 7 (6), pp. 394--400.

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