ELECTROCHEMISTRY AND PHOTOELECTROCHEMISTRY OF CHLOROPHYLL ON A METALLIC ELECTRODE .2. PHOTOREACTION OF ADSORBED CHLOROPHYLL

The insertion of a dielectric interlayer between a metal and a pigment was used to slow down electron exchange between the excited pigment and the metal. This increased the lifetime of the excited state and other non-equilibrium states and permitted primary charge separation and the involvement in the process of some component of the solution. In the system metal/monolayer of cetyl alcohol/ chlorophyll, appreciable photocurrents (up to 300 mu A cm** minus **2) were realized. Depending on the potential and on the presence of electron donors or acceptors in the solution, both anodic and cathodic photocurrents were obtained at the same electrode. Under different conditions, chlorophyll or some product of its transformation can play the role of a photoactive component. Different reaction pathways are possible, each of them including some step with an electron tunnelling through the dielectric film.