Electron
Microscopy image depicting the Palladium- Magnesium Oxide core-shell
combination.
The white dots are Palladium nanoparticles. The slight haze around
each nanoparticle is
the porous magnesium oxide shell. The Palladium
nanoparticles are not sintered together
and maintain spaces between each
another because of these shells. This maximizes
their ability to react with
chemicals.
(August 7, 2015)
There are no magic bullets for global energy needs. But fuel cells in
which electrical energy is harnessed directly from live, self-sustaining
chemical reactions promise cheaper alternatives to fossil fuels.
To facilitate faster energy conversion in these cells,
scientists disperse nanoparticles made from special metals called ‘noble’
metals, for example gold, silver and platinum along the surface of an
electrode. These metals are not as chemically responsive as other metals at the
macroscale but their atoms become more responsive at the nanoscale.
Nanoparticles made from these metals act as a catalyst, enhancing the rate of
the necessary chemical reaction that liberates electrons from the fuel. While the nanoparticles are being sputtered
onto the electrode they squash together like putty, forming larger clusters. This compacting tendency, called sintering,
reduces the overall surface area available to molecules of the fuel to interact
with the catalytic nanoparticles, thus preventing them from realizing their
full potential in these fuel cells.
Vidyadhar Singh is
standing next to the advanced nanoparticle deposition system at OIST.
Research by the Nanoparticles by Design Unit at the Okinawa
Institute of Science and Technology Graduate University (OIST), in
collaboration with the SLAC National Laboratory in the USA and the Austrian
Centre for Electron Microscopy and Nanoanalysis, has developed a way to prevent
noble metal nanoparticles from compacting, by encapsulating them individually
inside a porous shell made of a metal oxide. The OIST researchers published
their findings in Nanoscale. Their work has immediate applications in the field
of nano-catalysis for the manufacturing of more efficient fuel cells.
The OIST researchers designed a novel system. They
encapsulated Palladium nanoparticles in a shell of Magnesium oxide. Then they
dispersed this core-shell combination on an electrode and measured the immersed
electrode’s abilities in improving the rate of the electrochemical reaction
that occurs in methanol fuel cells. They demonstrated that encapsulated
Palladium nanoparticles give a significantly superior performance than bare
Palladium nanoparticles.