Polymer-protected Pt/Ru bimetallic cluster catalysts for visible-light-induced hydrogen generation from water and electron transfer dynamics

Colloidal dispersions of platinum/ruthenium bimetallic clusters, as well as those of platinum and ruthenium monometallic clusters, were prepared by alcohol reduction and applied to visible-light-induced hydrogen generation in the electron transfer system of tris(bipyridine)ruthenium(II) dichloride/methyl viologen dichloride/metal cluster/ethylenediamine-tetraacetic acid disodium salt. Hydrogen generation rates are in proportion to the concentration of cluster metal to low concentration (about 10(-6) to 10(-5) mol dm(-3)), where the platinum/ruthenium bimetallic cluster is more active as a catalyst than platinum and ruthenium monometallic clusters, In addition, even the physical mixture of platinum and ruthenium monometallic clusters is more active than platinum and ruthenium monometallic clusters, Electron transfer rates from the methyl viologen radical cation to metal clusters were measured as well and compared with the hydrogen generation rates. Thus, both rates are in proportion to each other, suggesting that the hydrogen generation rate can be controlled by the electron transfer rate. (C) 1997 Elsevier Science B.V.