OXIDATION OF WATER WITH PHOTOCATALYST—I. REDUCTION OF ELECTRON ACCEPTORS IN WATER SOLUTION WITHOUT ADDITIONAL ELECTRON DONORS

Photoreduction of electron acceptors—myoglobin, hemin and methyl viologen—sensitized by eosin or methylene blue in water solution was studied. The rate of photoreduction of acceptors grows with increasing pH. At pH 9.0 quantum yield of myoglobin reduction reached 1.5%, whereas the efficiency of the low molecular weight acceptors—hemin and methyl viologen—was much lower. Control experiments demonstrated that buffer molecules and the protein moiety were not the source of electrons for the reduction. All the data support the conclusion that in the process under the study hydroxide ions of water appear to be the linal electron donors.