PHOTOSYNTHETIC MEMBRANES .22. ENERGY-CONVERSION EFFICIENCY OF PHOTOELECTROCHEMICAL CELLS EMPLOYING A TITANIUM-DIOXIDE FILM ANODIC MEMBRANE AND A HYDROGEN OR OXYGEN CATHODE

Energy conversion efficiencies at various wavelengths in the range 315-420 nm were evaluated at 25 +/- 2 degrees-C in two types of photoelectrochemical cell, both involving a titanium dioxide film anodic membrane and 1 N NaOH as anolyte. In the first type, platinum black in 1 N H2SO4 was the counterelectrode (photoassisted energy conversion), whereas in the second type a platinum black cathode in 1 N NaOH worked self-regeneratively. The short-circuit current densities and open-circuit voltages were measured. Quantum efficiencies were also obtained. A comparison of the experimental values obtained in this study with those of conventional cells (titanium dioxide electrode not immobilized in a composite membrane structure) shows that no substantial difference is observed (outside experimental uncertainty) in the quantum and energy conversion efficiencies and open-circuit voltages. However, short-circuit current densities are systematically 13%-26% lower. This small effect can be attributed to a moderate increase in resistance brought about by the polymeric membrane. The performance and feasibility of photoelectrochemical membrane cells are discussed.