Thursday, March 20, 2008

CO/Hydrogen Separation

New research out of the University of Wisconsin (Madison) has shown a significant step forward in fuel cell design. A fuel cell is envisioned to be used in a car either to use stored energy in a hydrogen bond to power a battery to run the car as the hydrogen reacts with oxygen to form water, or a fuel cell can be run on a hydrocarbon such as diesel along to create the hydrogen and power the battery with water and carbon dioxide emitted in that case. What these researchers found was that when hydrocarbons are used, the catalysts used to drive the reaction in the batteries would be "poisoned" because of the carbon monoxide binding to the platinum catalyst. Once these expensive catalysts are poisoned, they no longer efficiently react with hydrogen and oxygen to form water and produce electricity.
In an effort to curb this problem, Bryan Eichhorn and Manos Mavrikakis designed a special nanoparticle that wants to oxidize CO to CO2 in the presence of hydrogen. First of all, a nanoparticle is simply a small molecule or compound that is very small -- nanometers in length. And the term oxidize refers to the addition of an oxygen atom to the molecule or the removal of a hydrogen atom from a molecule. In this case, the nanoparticle catalyst wants to add an oxygen atom to CO to produce CO2. The researchers did this by using a particle of ruthenium surrounded by one or two layers of platinum. The researchers discovered the nanoparticle uses a novel chemical reaction mechanism that actually makes hydrogen react with oxygen at the start of the reaction. This intermediate then more easily adds an oxygen atom to CO and leaves the hydrogen unreacted to be used in the fuel cell reactions. Also, the addition of the ruthenium particle necessitates reaction temperatures only as high as 30C, which is much less than the 85C that past catalysts have required in order to oxidize CO in the presence of hydrogen.
Although this process is very interesting for fuel cell design, I think the study is a much more important showcase for biochemical ingenuity. By uncovering this new reaction mechanism, new enzymes/nanoparticle catalysts could be developed to further this process. Also, many lab and companies deal with gas stream separation on a daily basis; having the right kinds of tools to deal with the problem is essential and could allow for much more efficient reactions to take place.

For original paper, follow this link:;jsessionid=3FF0F02A8B76048826E3326602E98BCD