Fuel cell technology offers a highly efficient and environmentally safe method of electricity generation. However, many of these cells require expensive Platinum catalysts. Therefore, to reduce the costs of fuel cells, more efficient catalysts must be synthesized. Metal clusters containing small numbers of atoms are an exciting class of material that may offer catalytic performance superior to other coarse and ultrafine particles. Highly stable metal particles with a set number of atoms, known as ‘magic number’ clusters, are relatively easily synthesized. However, it is thought that less stable, ‘non-magic-number’ clusters may exhibit enhanced catalytic activity. We have now succeeded to synthesise the the ‘non-magic-number’ platinum clusters by a dendrimer-templated approach.^{[1, 2]}
The catalytic performance varied considerably with the number of atoms in the clusters, with Pt₁₉ exhibiting the best performance for oxygen reduction reaction (ORR).^[3] The experimental results and theoretical analysis reveal that larger clusters feature Pt₁₃ cores with excess Pt atoms distributed at the edges. While symmetrical, magic-number Pt₁₃ clusters have low catalytic activity, the addition of edge Pt atoms to this stable core produces clusters with unexpectedly high catalytic activity. The changes in activity are related to changes in the shape of the cluster that depend on the number of atoms
[1] K. Yamamoto, T. Imaoka, et al. Nature Chem. 2009, 1, 397-402. [2] T. Imaoka, et al. J. Am. Chem. Soc. 2013, 135, 13089-13095.
[3] T. Imaoka, et al. Angew. Chem. Int. Ed. 2015, 54, 9810-9815.