Polymer Supported Metal Colloids as Catalyst

As described in Section 3 of Chapter 2, multi-electron processes are important for designing conversion systems. Noble metals are most potent catalysts to realize a multi-electron catalytic reaction. It is well known that the activity of a metal catalyst increases remarkably in a colloidal dispersion. Synthetic polymers have often been used to stabilize the colloids. Colloidal platinum supported on synthetic polymers is attracting notice in the field of photochemical solar energy conversion, because it reduces protons by MV to evolve H2 gas.la) 

Immobilization of the colloidal catalyst on resins was studied in order to use them repeatedly as stable solid catalyst. The citric acid reduction of poly(hydroxyethyl-methacrylate) containing H2PtCl4 yielded immobilized Pt colloids which are dispersed in that polymer57. It could be used as H2 generating catalyst repeatedly without activity loss in the system of EDTA-Ru(bpy)3 + -MV2 +.  

These metal and metal oxide catalysts must work as a kind of electron pool which brings about multi-electron process for H2 and 02 generation. Silver colloids were studied as electron pool for H2 formation under y-irradiation in the aqueous system composed of Ag° colloids, acetone, 2-propanol and SDS S9). The colloids (average diameter 140 A) of 2.5 x 10 4 M can store 1 coulomb/1, corresponding to the storage of 450 electrons/particle 60  

A colloidal polynuclear metal complex was proved to be an effective catalyst for water photolysis in combination with Ru(bpy)3 probably because its capability of multi-electron process. The details are described in the next chapter. 

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