WASHINGTON - University of Wisconsin-Madison researchers are working towards developing better catalyst for fuel cells in a bid to make clean cars a reality.
If successful, the researchers could make a car that runs on hydrogen from solar power, and produces water instead of carbon emissions.
Materials science and engineering assistant professor Dane Morgan and Ph.D. student Edward (Ted) Holby have developed a computational model that could optimise an important component of fuel cells, making it possible for the technology to have a more widespread use.
The researchers investigated how particle size is related to the overall stability of a material, and showed with their model that increasing the particle size of a fuel cell catalyst decreases degradation and therefore increases the useful lifetime of a fuel cell.
Fuel cells are electrochemical devices that facilitate a reaction between hydrogen and oxygen, producing electrical power and forming water.
In the type of fuel cells Morgan is researching, called proton exchange membrane fuel cells (PEMFCs), hydrogen is split into a proton and electron at one side of the fuel cell (the anode).
The proton moves through the device while the electron is forced to travel in an external circuit, where it can perform useful work, while at the other side of the fuel cell (the cathode), the protons, electrons and oxygen combine to form water, which is the only waste product.
One of the many hurdles to producing efficient fuel cells for widespread use is the catalyst added to aid the reaction between protons, electrons and oxygen at the cathode.
Current fuel cells use platinum and platinum alloys as a catalyst. While platinum can withstand the corrosive fuel cell environment, it is expensive and not very abundant.
Thus, to maximize platinum use, researchers use catalysts made with platinum particles as small as two nanometers, which are approximately 10 atoms across.
These tiny structures have a large surface area on which the fuel cell reaction occurs.
However, platinum catalysts this small degrade very quickly, which means that the fuel cell doesn’t last long.
The researchers have found a possible solution to the rapid degradation problem-when it comes to catalyst particle size, sometimes smaller isn’t better.
In their modelling work, they showed that if the particle size of a platinum catalyst is increased to four or five nanometers, which is approximately 20 atoms across, the level of degradation significantly decreases.
This means the catalyst and the fuel cell as a whole can continue to function for much longer than if the particle size was only two or three nanometers.
“Fuel cells are just one of many energy technologies - solar, battery, etc. - with enormous potential to reduce our dependence on oil and our carbon emissions. Computer simulation offers a powerful tool to understand and develop new materials at the heart of these energy technologies,” said Morgan. (ANI)
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