Nanoparticles are increasingly finding applications in high-tech products, but remain difficult to produce reliably. Researchers at Edinburgh University, working with the Californian Institute of Technology, have now devised a method to make nanofibres “decorated” with mineral nanoparticles, and have incorporated this material into working fuel cells.
Electrospinning is most familiar as the technique which produces fine threads of sugar from a syrup in fairground candyfloss machines. It uses electric fields to draw charged threads from a solution or a molten polymer, with electrostatic repulsion overcoming the surface tension of liquid droplets to elongate them into nanofibres with diameters typically around a couple of hundred nanometres.
The Edinburgh team, led by Norbert Radacsi, used a solution of polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA), and a small amount of polyaniline (PANI), into which was mixed caesium dihydrogen phosphate (CDP), an electrolyte used in solid oxide fuel cells. They turned this into fibres using a nozzle-free electrospinning technique which, they explain in a paper in Nature Communications, enhances the yield of nanofibres. The technique applies a high-voltage to a rotating drum in a bath of liquid at high temperature; the fibres are produced from the liquid on the surface of the drum and are spun onto an adjacent hot surface. As the fibres cool, nanocrystals of CDP emerged spontaneously on their surface. The fibres were around 120nm in diameter, and the particles around 105nm. The particles appeared both on the surface and in the interior of the fibre.
Radacsi and colleagues incorporated these fibres into an experimental fuel cell, which they claim performed better than a CDP-containing fuel cell produced by conventional means. "Our approach of electrospinning offers a quick and inexpensive way to form nanomaterials with high surface area. This could lead to products with improved performance, such as fuel cells, on an industrial scale," Radacsi said.
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