Nano catalysts Hydrogen Fuel cells
Neeraj Kumar (B10024)
Vihari Piratla (B10025)
Submitted as a part of assignment for the course of CY241 Autumn semester 2013
Hydrogen fuel cells can be an efficient and alternate source of power, as some of
the variants of hydrogen fuel cells doesn’t produce greenhouse gases. The energy efficiency of
a fuel cell is generally between 40–60%, or up to 85% efficient if waste heat is captured for use.
Hydrogen is a most common fuel for its source is abundant.
Though Hydrogen fuel cells are efficient and lucrative sources of energy, much of
the capability is untapped for cost reasons. 40% of the cost of the Hydrogen fuel cell(HFC) is
because of the Platinum(Pt) cathode catalysts and the other reason stems from the intolerance
of catalyst towards CarbonMonoxide(CO). It is observed that CO concentration so low as few
10’s or 100’s of ppm can poisson the catalyst by reducing the active sites and hence reducing
the catalytic capacity and efficiency. This intolerance of catalyst towards CO renders common
way of hydrogen production through steam reforming of light useless as it contains CO to 13%,
hence forcing one to produce hydrogen by electrolysis of water. Because of the high cost of
HFC’s they are not yet successful in replacing IC engines.
The U.S. Department of Energy estimates that platinumbased catalysts will need
to use roughly four times less platinum than is used in current PEM fuel cell designs in order to
represent a realistic alternative to internal combustion engines. Research is being carried out
with the following goals:
1. To increase the efficacy of the catalyst, the catalysts efficiency should be increased at
least 4 times to be able to replace IC engines.
2. To make it more tolerant to impurities like CO, even CO in ppm amount can poisson the
catalyst and render the catalyst useless. Generally high temperature Fuel cells are used
to avoid the catalyst poisoning(one of the variants of Fuel cells).
3. To design a metal free catalyst model that can be easily synthesised, with alloys or
composites that are copiously available, tolerant to CO poisonous and less degrading
While these are some of the factors that stood as impediments, the research area has seen
some game changers.
Some game changers being nano technology and other nano imaging techniques
these help in better and more control over synthesis of defect less and desired amalgamate of
the various elements.
Also better imaging techniques mean that one can observe the adsorption and surface
absorptions better and this can help in better synthesis of the heterogeneous
Hydrogen has a high energy density and is a great energy carrier, Schaak said, but it requires
energy to produce. To make its production practical, scientists have been searching for a way to
trigger the required chemical reactions with an inexpensive catalyst.
1. Since then there has been a lot of research for a non metallic alternate to Pt and also
ways to 1. increase active sites in the catalyst either by occluding the Pt atoms on a nano
2. Pt occlusions on other metals/elements to make it more CO tolerant.
3. Good amount of research also on testifying structures like Carbon nano tubes, edge
halogenated graphene nano platelets, nickel phosphide nano structures and were also
We shall discuss some very recent research efforts in this direction.
Ru–Pt core–shell nanoparticle:
This section constitutes the summary of .
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 highperforming 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
coreshell structure ruthenium coated with platinum resists damage from carbon monoxide
and also reduces the Pt consumption by 98%. In specific the paper also talks about the
tradeoffs between various amalgamation types of Pt with Ru/Ir/Rh/Pd/Au. Alloy coreshell and
linked monometallic nano particle structures were considered. It was also concluded that
coreshell structures of RuPt has the best efficiency both in terms of cost and active sites. The
paper attributes that recent advances in surface science techniques, analytical instrumentation
and firstprinciples calculations provide mechanistic insight into the atomistic surface chemistry
governing the catalytic activity and over the groundwork for true rational design of heterogeneous
catalysts. Throughout this research STEM images enhanced with Density Functional
Theory(DFT) were used to characterise and observe histogram of particle sizes in various
heterogeneous structures.The carbon monoxide impurities in hydrogen formed from natural gas
present another challenge to scientists because they deactivate most platinum catalysts.
Ruthenium less expensive than platinum promotes carbon monoxide tolerance, but is more
prone to dissolution during fuel cells' startup/shutdowns, causing gradual performance decay.
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. 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. 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
TPRresultsforthedifferentPt–RucatalystsshowingH2OformationversustemperatureforH2 feeds contaminated by
0.1% CO by volume. The H2 O yields are plotted as % maximum formation based on the limiting reactant O2 . With
complete CO conversion in the 0.1% CO feed, the maximum formation of water is 90%. The monometallic Pt
remains in the baseline in this temperature range and does not light off until 170 C.
Figure2: A schematic
synthesis of XGnP’s.
Facile, scalable synthesis of
nanoplatelets as efficient
metalfree eletrocatalysts for
oxygen reduction reaction:
This section summarises .
This paper published in June
2013, proposes edge
nanoplatelets 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
Hetro atom or covalently bonded atoms can better function in Oxygen Reduction
reaction(ORR). The difference in electronegativity (x) between the heteroatom dopants (B =
2.04, I = 2.66, N = 3.04, P = 2.19 and S = 2.58) and carbon atom (2.55) in covalently doped
graphitic carbon frameworks can polarize adjacent carbon atoms. Indeed, 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 verticallyaligned nitrogendoped carbon
nanotubes (VANCNTs) and nitrogendoped graphene (Ngraphene) catalyzed an efficient
fourelectron ORR process with a higher electrocatalytic activity and better operation stability
than the commercially available Pt/Cbased electrocatalyst (Pt: 20 wt%, Vulcan XC72R). Many
of these were untapped because of their intricate synthesis processes and here in this paper
authors propose a very simple and scalable synthesis that is ball milling of graphite with halogen.
Figure 2 shows and summarises the synthesis step. The order of Electrocatalysis observed
was IGnP>BrIGnP>ClGnP, where XGnP is X halogenated grapheme nano platelets.
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. When methanol was added to replicate methanol crossover from the anode to
cathode in direct methanol fuel cells, the current density of the platinum catalyst dropped
sharply. Again, the graphenebased catalysts were unaffected. Also in comparison with the Pt/C
commercially available catalyst: a cathode coated with iodineedged nanoplatelets performed
best. A cathode coated with bromineedged nanoparticles generated 7 percent less current than
the commercial cathode coated with platinum, the chlorineedged nanoplatelets 40 percent less.
In conclusion, a metalfree 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 nanocatalyst, the scope of commercialisation is very
Electrocatalyst based on carbon nanotubesgraphene complexes
This section summarises .
Although this paper doesn't aim at commercially replacing Pt/C, it obviates some
misconceptions and also proposes a new nano catalyst based on carbon nanotubes whose
catalytic activity is close to platinum and thus considered relevant.
For the study, the Stanford team used multiwalled carbon nanotubes consisting of two
or three concentric tubes nested together. The scientists 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.
The multiwalled carbon nanotube is treated to unzip outer wall and is as depicted in
figure3. 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. The research also concluded
that metal impurities play a major role in the catalysis and can't be ignored.
NanoPhosphide based nano catalysts
This section constitutes information from .
According to a team lead by Chemistry professor in Penn state University and patent
filed, NickelPhosphide nano particles in solution has produced current at a greater efficacy than
Pt/C counterpart. This was possible because of very high surface area in nanoparticles and
increased number of active sites.
Though it is implied that it will be lot cheaper than Pt/C, it is unknown the effect of
impurities in Hydrogen source on the catalyst. It is also unknown the durability of the catalyst.
The research group states their future goal as to further improve the performance of these
nanoparticles and to understand what makes them function the way they do.
We are evidencing a revolution in the research of nano catalysts with the advent of
Nanoscience 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.
We have seen metalfree catalysts that can function just as well as Pt/C and also have
seen modification to Pt catalysts to nanocatalysts to improve the robustness and alleviate cost.
We feel that the results that were presented here suffices for large scale
commercialisation of Hydrogen Fuel cells. 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 greenhouse gases. We feel the only
possible piece of puzzle that needs to be solved is efficient(Volume/weight ratio) and safe
storage of Hydrogen.
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