Light-induced charge separation and water cleavage in microheterogeneous aqueous systems

Abstract

This paper is concerned with reaction systems in which fuel production is achieved by illumination of aqueous solutions. Research interest in this field focuses on the photoredox reaction A + D [graphic omitted] A^–+ D⁺ in which A and D are solutes of which one is excited by light. Major problems to overcome for practical use of these systems are the retardation of the back reaction and the production of fuel from the intermediates A^– and D^+. Micellar aggregates may be employed for the kinetic control of forward and backward reaction. Here, through judicious choice of the molecular system, in particular the use of functional electron relays, charge separation can be achieved. This concept has been coupled with the use of colloidal redox catalysts to bring about hydrogen and oxygen formation from water, A^–+ H₂O [graphic omitted] ½H₂+ OH^–+ A, 2D⁺+ H₂O [graphic omitted] 2H⁺+½O₂+ 2D., Systems which produce hydrogen and/or oxygen from water through illumination with visible light will be reviewed and most recent experimental results from our and other laboratories discussed.