Polymer-protected bimetallic nanocluster catalysts having core/shell structure for accelerated electron transfer in visible-light-induced hydrogen generation

A visible-light-induced electron transfer system was constructed by using tris(bipyridine)ruthenium(III), methyl viologen, EDTA and colloidal metal nanocluster as photosensitizer, electron relay, sacrificial electron donor and reductive catalyst, respectively. Polymer-protected Au, Pt, Pd, Rh and Ru monometallic, and Au/Pt, Au/Pd, Au/Rh and Pt/Ru bimetallic nanocluster catalysts were prepared as colloidal dispersions by alcohol-reduction, and applied to the catalysts for the above reaction. The rate of electron transfer from methyl viologen cation radical to the metal nanocluster catalyst is proportional to the hydrogen generation rate at a steady state. All the electrons accepted by metal nanocluster catalysts are used for the hydrogen generation. Both electron transfer and hydrogen generation rates increase when the colloidal dispersions of bimetallic nanoclusters are used in place of the corresponding monometallic nanoclusters. An Au-core/Rh-shell structure has been suggested by UV-Vis spectrum measurement for Au/Rh bimetallic nanoclusters.