Photoreduction of water by visible light in the presence of montmorillonite

Abstract

A pH 7.0 solution of methyl viologen, tris(2,2′-bipyridyl)ruthenium(II) chloride and triethanolamine acting as a sacrificial donor, produces hydrogen when irradiated by visible light ( > 395 nm) in the presence of a montmorillonite. We have observed a maximum production of hydrogen corresponding to an optimum ratio methyl viologen/clay. Preferential adsorption studies have allowed us to relate this optimum ratio to a particular distribution of the dicationic organic species on the clay surface: methyl viologen is intercalated into the layers and shares the occupancy of the external surface area in a ratio three-to-one with tris(2,2′-bipyridyl)ruthenium(II). Nine different homoionic clays were prepared and, compared to the natural one, showed no drastic difference in the hydrogen production.