Changing catalytic activity during colloidal platinum nanocatalysis due to shape changes: electron-transfer reaction.

The shape distribution of the catalytic nanoparticles and the activation energy of the electron-transfer reaction between hexacyanoferrate (III) and thiosulfate ions were determined at different times during the course of the reaction. The activation energy is found to increase during the reaction when dominantly tetrahedral nanoparticles are used, decreases slightly when dominantly cubic nanoparticles are used, and remains almost unchanged when spherical nanoparticles are used. Corresponding changes in the shape of the tetrahedral and cubic, but not spherical, shape is observed. This is consistent with the changes in the activation energy that are observed. The shape distribution and activation energy of dominantly spherical nanoparticles is found to remain stable during the course of the reaction.