Fuel cells have become a favorable future power source because they can convert chemical energy directly into electricity in a highly efficient, environmentally friendly manner. Although fuel cells were invented one and a half centuries ago, only recently has it become feasible for them to compete with existing energy production systems. Among the various types of fuel cells, proton exchange membrane (PEM) fuel cells promise to become a viable power source for transportation as well as a distributed power source for residential uses because of their low operating temperatures and high power density. PEM fuel cells also promise to become an alternative to batteries in portable electronics, such as laptop computers, cellular phones, and other hand-held devices. The catalysts currently used in PEM fuel cells are Pt nanoparticles supported on carbon black. Pt as a precious metal is expensive, and there have been tremendous efforts made to reduce its usage. One way is to make Pt nanoparticles as small as possible to maximize the catalyst dispersion and thus its utilization. Smaller nano particles provide larger specific surface areas for electro catalytic reactions that only occur on the surface of the catalysts PEM fuel cell catalysts are generally produced by precursor impregnation methods in which a Pt salt precursor is impregnated into carbon black, followed by high-temperature oxidation and reduction. Impregnation methods are simple and suitable for large scale productions; however, it is difficult to achieve both high Pt dispersion (small particles) and high metal loadings at the same time. High metal loading generally comes with larger particles. Here, we report a technique using a polymer, poly-(vinylpyrrolidone) (PVP), in a polyol (ethylene glycol) solution to mediate the size of Pt nanoparticles and control their size distribution.
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