Studies of a photosynthetic photoelectrochemical cell using various electrodes

We have developed a photochemical cell using a combination of photosynthetic electron transport (photosystem I particles) and the photoreduction of a dye such as flavin mononucleotide (FMN) (6). The overall power conversion efficiency depends on the rate of charge transfer across the electrode surfaces in addition to the efficiency of the photosynthetic and photochemical reactions. For this reason, we studied the effect of varying the nature of the electrodes on the power developed. We found that reticulated vitreous carbon electrodes showed higher power conversion efficiencies than did nickel mesh, platinum, or SnO₂ glass. There are two reasons for this. First, the ratio of actual to apparent surface area is greater for RVC electrodes than for the others. Second, FMN and its photoproducts react better with carbon than platinum electrodes. Substituting RVC electrodes for platinum increased the power conversion efficiency from 1.0 to 3.9%. Platinizing platinum, nickel mesh, or brass electrodes also increased the power developed. However, the photopotential remained stable for several hours only for the platinized platinum electrodes.