Kinetics of electron-transfer catalysis

The catalytic role of metal clusters such as Tl, Ag , Au , and in electron 

Pulse radiolysis also enables the observation of some catalytic electron-transfer reactions other than the autocatalytic growth (Eqs. 42-44). Electron transfer from MV to protons in water requires the presence of a catalyst, for example platinum clusters. The initial electron transfer step (Eq. 42) from MV+ to the cluster was found to be diffusion-controlled  

For a given amount of metal the transfer rate increases linearly with particle concentration. The rate-determining step is clearly the desorption of molecular hydrogen.  

The catalysis of the disproportionation of the superoxide anion 02 by Pt clusters in subcolloidal solutions or supported on colloidal Ti02 particles has also been studied by time-resolved techniques.The decay of 02 follows first-order kinetics in respect of both 02 and the Pt clusters because the catalysis is governed by the proton concentration adsorbed at the cluster surface. 

The specific approach of the studies described in this review has been to investigate the elementary mechanisms and the thermodynamics of the atom formation, of cluster nucleation and growth, and of their reactions. 

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