PHOTOELECTROCHEMICAL DECOMPOSITION OF WATER UTILIZING MONOLITHIC TANDEM CELLS

Photovoltaic tandem cells consisting of a gallium indium phosphide (Ga InP2) homojunction grown epitaxially upon a gallium arsenide (GaAs) ho mojunction, with a GaAs tunnel-diode interconnection were utilized to photoelectrochemically decompose water in a 1 M sulfuric acid electrol yte solution. Using a sol-gel process, a platinum colloid in water was used to modify the illuminated front surface of the device to catalyz e the water decomposition process. A unique feature of this device is that the hydrogen and oxygen are co-evolved from the illuminated surfa ce. The exact mechanism of the water decomposition process is not full y understood at this time. (C) 1998 Published by Elsevier Science B.V. All rights reserved.