Oxygenic photosynthetic biological material, such as purified photosystems or whole algal or cyanobacterial cells, are employed in the anodic half-cell. These organisms are able to use light energy to drive the oxidation of water, and a fraction of the electrons produced by this reaction are transferred to the extracellular environment, where they can be used to reduce an anode. No heterotrophic organisms are included in the anodic chamber - electrode reduction is performed directly by the photosynthetic material.