As the global community seeks to develop alternative energy sources to supplement, extend, and replace traditional fossil-based energy resources, fuel cells have drawn much attention due to their large inherent efficiency for energy conversion. PEM (polymer electrolyte membrane) fuel cells have existed for a long time, and while there has been significant development, there are still major drawbacks that limit further development and applications of fuel cells on a large scale. First, fuel cells are expensive partly due to the use of costly Pt and Pt-based catalysts, and the natural abundance of Pt is too low to support large scale use of fuel cells with Pt as an electrocatalyst Second, Pt-based catalysts are poisoned by impurities such as CO, H2S, and NH3, in fuels, and these impurities seriously reduce the activity of catalysts, thus shortening their lifespan. Third, the sluggish oxygen reduction reaction (ORR) kinetics at the cathode (due to the large overpotential) causes relatively low current density and thus limits the power of fuel cells. Fourth, while direct ethanol fuel cells would benefit from the advantages in fuel production, transportation, storage, and volumetric energy density of ethanol over hydrogen, no catalyst can completely Oxidize ethanol in high efficiency. Solutions to these problems relies on the discovery and tailoring of an optimal catalyst with attributes of high activity, durability, low cost, and resistance to negative effects of impurities in the fuel.
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