Connected nanoparticle catalysts possessing a porous, hollow capsule structure as carbon-free electrocatalysts for oxygen reduction in polymer electrolyte fuel cells

We employ connected nanoparticle catalysts with a porous, hollow capsule structure as carbon-free electrocatalysts for the cathode in polymer electrolyte fuel cells (PEFCs) or proton exchange membrane fuel cells (PEMFCs). The catalysts consist of fused ordered alloy platinum–iron (Pt–Fe) nanoparticles. This unique beaded network structure enables surprisingly high activity for the oxygen reduction reaction, 9 times that of the state-of-the-art commercial catalyst. Because the connected nanoparticle catalysts are formed without sacrificing the high surface area of the nanoparticles and can conduct electrons, the catalysts show good performance in an actual PEMFC without a carbon support. Moreover, the elimination of carbon intrinsically solves the problem of carbon corrosion. Thus, the connected nanoparticle catalysts with a unique structure are a significant advancement over conventional electrode catalysts and will lead to an ultimate solution for PEMFC cathodes.