Photoelectrocatalytic production of hydrogen from natural seawater under sunlight

It is shown, for the first time, that hydrogen can be produced photoelectrocatalytically from natural seawater under sunlight at ambient temperature without the assistance of externally applied bias potential by the use of a materially optimized thin film transparent titania photocatalyst. A SUPEC (single unit photoelectrocatalysis) cell, combining the thin film photocatalyst and an electrocatalyst into one sheet, is constructed to produce hydrogen at a rate of 0.4 liter h(-1) given a 1 m(2) cross-sectional area of sunlight irradiation on the photocatalyst. The photocatalyst remains stable and active in natural seawater. Also, quantum efficiency for photon-to-current conversion, measured in natural seawater under a constant photon irradiation and without bias potential, reached 54% as the wavelength was varied systematically. Both the hydrogen production rate and the quantum efficiency are at the same level as in the case with a typical electrolyte such as potassium bicarbonate solution. Seawater is a natural electrolyte solution which can be used without modification for photocatalytic water decomposition. (C) 1997 International Association for Hydrogen Energy.