Spinach Provides Gasoline Cells a Energy Up – Slashdot


Researchers at the Department of Chemistry, American University, used spinach to make a carbon-rich catalyst that can be used to improve the performance of fuel cells and metal-air batteries. IEEE Spectrum reports: The spinach was a used a precursor for high-performance catalysts required for the oxygen reduction reactions (ORRs) in fuel cells. Traditionally, fuel cells have used platinum-based catalysts, but not only is platinum very expensive and difficult to obtain, it can be vulnerable to chemical poisoning in certain conditions. Consequently, researcher have looked into biomass-derived, carbon-based, catalysts to replace platinum, but there have been bottlenecks in preparing the materials in a cost-effective and non-toxic way. “We were a little bit lucky to pick up spinach,” says [Shouzhong Zou], because of its high iron and nitrogen content. “At this point [our method] does require us to add a little bit more nitrogen into the starting material, because even though [spinach] has a lot of nitrogen to begin with, during the preparation process, some of this nitrogen gets lost.”

The preparation of the spinach-based catalyst sounds as first suspiciously like a smoothie recipe at first — wash fresh leaves, pulverize into a juice, and freeze-dry. This freeze-dried juice is then ground into a powder, to which melamine is added as a nitrogen promoter. Salts like sodium chloride and potassium chloride — “pretty much like the table salt that we use in our kitchen,” says Zou — are also added, necessary for creating pores that increase the surface area available for reactions. Nanosheets are produced from the spinach — melamine — salt composites by pyrolyzing them at 900 C a couple of times. “Obviously… we can optimize how we prepare this material [to make it more efficient].”

An efficient catalyst means a faster, more efficient reaction. In the case of fuel cells, this can increase the energy output of batteries. This is where the porosity of the nanosheets helps. “Even though we call them nanosheets,” Zou says, “when they are stacked together, it’s not like a stack of paper that is very solid.” The addition of salts to create tiny holes that allows oxygen to penetrate the material rather than access only the outer surfaces. “We need to make it porous enough that… all the active sites can be used.” The other factor that favorably disposed the American University team towards spinach was that it is a renewable source of biomass. “Sustainability is a very important factor in our consideration,” says Zou. The big question to explore, he adds, is how can we avoid competition “with the dinner table.” (Biofuel production has already raised concerns about food crops being diverted away from hungry mouths.) “And the second is, how do we keep the carbon footprint down in terms of his catalyst preparation… because currently we do use high temperatures in our preparation procedure?” If we can find different ways to do these to achieve the same type of material, that will cut back the energy consumption and reduce significantly the carbon footprint.”

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