This investigation is trying to
replace platinum based catalytic systems with a nitrogen doped graphene. So far it appears that they are having some
real success and here report that they matching the platinum protocol. This is possibly huge for the fuel cell
business.
Platinum consumption has been the
one cost factor that has kept the fuel cell out of the market and why it is not
today powering your cell phone. Eliminate
that and the rest is mechanics and convenience.
Replacing platinum as a catalyst
has been on chemistry’s to do list for over a century. This may just do the trick or be so close
that it barely matters.
This will also kick the cost out
of a lot of process chemistry.
Let us be serious – there has
never been a next generation catalyst to compete with platinum.
N-graphene: a next-generation catalyst
16 May 2011
Nitrogen doped graphene has the potential to become a cheap and durable
electrocatalyst
Energy shortages and environmental pollution are serious challenges
that humanity is now starting to face. Proton exchange membrane fuel cells
(PEMFCs) are non-polluting and efficient energy conversion devices that are
expected to play a dominant role in future energy solutions. However, current
PEMFC systems still face significant technological roadblocks which must be
overcome before the system can become economically viable. A major impediment
to the commercialization of PEMFCs is the high cost and stability of Pt-based
electrocatalysts. In collaboration with Ballard Power Systems, researchers from
the Nanomaterials and Energy group at the University
of Western Ontario , Canada , have
discovered a new metal-free catalyst, nitrogen doped graphene (N-graphene), that
could make fuel cells more cost effective and stable. [D. Geng et al.,
Energy Environ Sci (2011) 4, 760].
Recent studies on reducing or replacing Pt-based catalysts in fuel
cells have indicated that nitrogen-doped carbon materials could act as effective
metal-free electrocatalysts, although the real active site remains unclear.
Graphene, a new 2-dimensional carbon material, not only possesses a high
surface area and excellent conductivity, it also has a unique graphitic basal
plane structure. It is well known that the greater the extent of graphitization
of the carbon material, the greater the durability it demonstrates. The unique
properties of nitrogen-doped graphene prompted the researchers to investigate
the electrochemical activities of nitrogen-doped graphene.
N-graphene has been synthesized on a large scale, using ammonia and the
heat treatment of graphene. The method overcomes the shortcomings of chemical
vapor deposition, which is difficult to scale up, and therefore limits the wide
use of N-graphene for electrodes. The new method makes it possible for membrane
electrode assemblies to be easily fabricated, and allows the extent of the
electrocatalytic activity to be accurately identified. The activities of
N-graphene electrodes and commercial Pt/C catalyst electrodes can be directly
compared, as the exact catalyst loading is known.
Importantly, the nitrogen content can be controlled by changing the
ammonia heat-treatment temperature. N-graphene has exhibited comparable, or
better, activity and stability than commercial Pt/C (loading: 4.85 mgPt cm-2) towards
the oxygen reduction reaction (ORR). XPS analysis indicates that quaternary
type nitrogen species seem to play the most important role for ORR activity.
Therefore, N-graphene as next-generation catalysts may have the potential to
replace the costly Pt/C catalyst in fuel cells.
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