August 7, 2015

Pouring Fire on Fuels at the Nanoscale

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.