1 Jello-making protein could help make cheap fuel cells on Fri Nov 29, 2013 10:04 pm
New research shows that a catalyst made using gelatin, the same protein used to make jiggly desserts, helps fuel cells be more efficient. This may offer a cheap alternative to fuel cells that require precious metal catalysts.
In a fuel cell, energy released from a chemical reaction (most commonly hydrogen and oxygen combining to form water) is diverted and used to generate electricity. Many carmakers are looking to test a commercially viable fuel cell. If their tests are successful, cars of the future will spit out only water, without the carbon dioxide and other pollutants that today’s fossil fuel powered cars emit.
Researchers from the UK, Japan, and China, led by Zoe Schnepp at the University of Birmingham, reported their new catalyst in the Journal of Materials Chemistry A. To make the catalyst, they mixed salts of magnesium and iron with gelatin to create a foam. Heating this foam to 800°C triggers a process called calcination, which degrades the gelatin and oxidizes the metals. This results in a sponge that contains metal nanoparticles (which are a million times smaller than a human hair) embedded in a porous structure made of carbon. Any remaining metal is washed off with acid.
This porous structure is an advantage for the catalyst. The network of pores and bubbles inside it provides a very large surface area for chemical reactions to occur. The choice of metal salts proved to be important, too, since the metals determined the size of the pores and thus affected the reactions. The two metals used react differently during calcination: the magnesium is converted to nanoparticles of magnesium oxide, while the iron bunches together into much larger particles of iron carbide. This means that the ratio of magnesium to iron can be used to tune the pore size.
During heating, iron carbide converts the carbon around it to a thin sheet, which happens to be good for a fuel cell reaction. Nitrogen atoms from the gelatin become embedded in this thin sheet of carbon, and previous results have shown this makes the catalyst even more effective.
When Schnepp compared commercial platinum catalysts with hers, she found the new material did just as well. Crucially, the new catalyst is also as durable as the platinum ones. Platinum is extremely expensive, and, in recent years, there have been many efforts to find a cheaper and better alternative. Schnepp’s catalyst needs cheap gelatin and plentiful metal nitrate salts, making it one of the more compelling alternatives yet.
By exploiting the properties of biological polymers, Schnepp and colleagues have found a simple route to a structurally complex and useful material. Simplicity, as Steve Jobs would say, is often the first step to a great product.[You must be registered and logged in to see this image.]
Journal of Materials Chemistry A, 2013. DOI: 10.1039/C3TA12996A (About DOIs).]