The new type photoelectrochemical (PEC) cell for hydrogen production under sunlight in which polysulphide solution was oxidized at the photoanode and water was reduced at the cathode was proposed by us. This construction permits to use small bandgap semiconductors sensitive for visible solar light as photoanodes. Indium monoselenide, n-InSe with bandgap 1.2 eV was investigated for this purpose. It was established that hydrogen potential was not reached by electrode photopotential and photocurrent was associated with the photocorrosion of electrode. The influence of lithium ions intercalation into InSe volume and zinc atoms deposition on its surface on the photopotential was also investigated. The shift of dark- and light potentials to cathode direction under both these treatments was observed. But the photosensitivity of electrode decreased drastically under potentials closed to water reduction potential. From these data it was concluded that InSe had low promise as the photoanode material for PEC cell for hydrogen production.
The second photoanode investigated in the frame of the Project was hybrid photoanode based on TiO2 film and Si solar cell. TiO2 films were produced by the chemical vapor deposition (CVD) method. The new technique of production of continuous CVD TiO2 films on semiconductor surface was proposed. The peculiarity of this technique is deposition of a thin (30-40 nm) Ti layer on the substrate prior to TiO2 deposition. This metal layer serves as the catalyst of following TiO2 film growth and then it is oxidized itself to TiO2. Continuous TiO2 films obtained by such a way protect the solar cell surface from oxidation in the electrolyte. The optimal TiO2 film thickness and structure for highest photocurrent were determined. It has been shown that the use of a metal-hydride cathode based on LaNi5 alloy instead of a Pt cathode increases significantly (up to 50%) the solar cell efficiency. The efficiency of solar-to-hydrogen conversion has attained 2% with the Pt cathode and 3% with the metal-hydride cathode that is the promising result.