A photoelectrochemical cell with oriented pigment-polymer complexes

Photoelectric properties of chlorophyll and carotene solutions in nematic liquid crystal located between semiconducting electrodes

The photopotential and photocurrent generation for chlorophyll a, beta-carotene and a mixture of these pigments dissolved in nematic liquid crystal and located between transparent semiconducting electrodes were measured. Both pigments exhibit photopotential and photocurrent generation. From the photocurrent amplitudes it follows that the efficiency of electron transfer to a semiconducting electrode from beta-carotene is higher than from chlorophyll alpha. The photocurrent amplitude of the pigment mixture is slightly lower than that calculated as a sum of amplitudes of pigments located in separated cells. This difference can be explained by secondary effects, such as competition between carotene and chlorophyll molecules in a process of adsorption on a semiconducting electrode. Therefore it seems that no charge transfer complexes of chlorophyll and carotene are formed in the investigated model system.

Hydrogen generation from artificial sea water in a semiconductor septum electrochemical photovoltaic cell

Visible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n-CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short-circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy.