Abstract: The product is in the form of discrete particles or in the form of a layer comprising an electrode. It consists of a semi-conductor material subject to photo-corrosion, for example, cadmium sulphide. In order to prevent such photo-corrosion, the surface of the semi-conductor material, which is intended to be illuminated, is covered with a transparent layer of RuO.sub.2, IrO.sub.2 or a mixture of RuO.sub.2 and IrO.sub.2.The product may be used for the conversion of solar energy into electric energy or into a fuel such as hydrogen.

Abstract: A photolytic system comprised of a darkened halfcell and an illuminated halfcell in which oxidation and reduction reactions are made to occur. These halfcells are joined by an electrically conductive element and an ion conducting junction for electron transfer and ion transport. The illuminated halfcell is equipped with a cathode and the darkened halfcell contains an improved anode which exhibits a desirably low overvoltage with respect to the substrate which is sought to be oxidized. Oxidation products are formed at the anode and reduction products are formed at the cathode.