Oct
29
A New Type of Catalyst For Fuel Cells
October 29, 2014 | Leave a Comment
The new type of catalyst is highly efficient at oxygen reduction, the most important reaction in hydrogen fuel cells. The team’s paper has been published in the scientific journal Nature Communications.
Fuel cell systems represent a promising alternative for low carbon emission energy production. But traditional fuel cells are limited by the need of efficient catalysts to drive the chemical reactions involved in the fuel cell. Historically, the rare mineral platinum and its alloys have frequently been used as anodic and cathodic catalysts in fuel cells, but the high cost of platinum due to its rarity, motivates researchers to find efficient catalysts based on more earth-abundant elements.
Thomas Wågberg, senior lecturer at Department of Physics, Umeå University said, “In our study we report a unique novel alloy with a palladium (Pd) and tungsten (W) ratio of only one to eight, which still has similar efficiency as a pure platinum catalyst. Considering the cost, it would be 40 times lower.”
A graphical schematic model of the unique structure of the palladium tungsten alloy. The Pd-islands (light-brown spheres) are embedded in an environment of tungsten (blue spheres). Oxygen are represented by red spheres, and hydrogen by white spheres.
Image Credit: Courtesy of Umeå Universitet. Click image for the largest view.
The reason for the very high efficiency is the unique molecular structure and features of the alloy. It is neither a fully mixed together homogeneous alloy, nor a fully segregated two-phase system, but rather its something in between.
Using advanced experimental and theoretical investigations, the researchers show that the alloy is composed of metallic Pd-islands embedded in the Pd-W alloy. The size of the islands are about one nanometer in diameter and are composed of 10-20 atoms that are segregated to the surface. The unique environment around the Pd-islands gives rise to special effects that all together turn the islands into highly efficient catalytic hot-spots for oxygen reduction.
To stabilize the nanoparticles in practical applications, they are anchored on ordered mesoporous carbon. The anchoring keep the nanoparticles stable over a long time by hindering them from fusing together in the fuel cell tests.
Now the concept gets very interesting:
Wågberg explains, “The unique formation of the material is based on a synthesis method, which can be performed in an ordinary kitchen micro-wave oven purchased at the local supermarket. If we were not using argon as protective inert gas, it would be fully possible to synthesize this advanced catalyst in my own kitchen!”
Looking good. Much lower cost palladium vs. platinum and a manufacturing process on the very low end of the potential.
Wågberg and his fellow researchers have recently received funding from the Kempe Foundation to buy a more advanced micro-wave oven so they will be able to run more advanced experiments to fine tune some of the catalyst properties.
The oxygen reduction reaction at the cathode side of proton exchange membrane inside of fuel cells is one of the major technical challenges to building mass market fuel cells. Today fuel cells are very expensive and admittedly, slow producers of energy output in electric current. For the transportation market the fuel cell just isn’t ready for prime time consumer demands.
Finding efficient yet cheap electrocatalysts to speed up this reaction is driving researchers the world over.
Maybe the Swedish and Chinese team have found the next solution to the fuel cell development track.
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