The conversion of solar energy into electrical current by photosynthetic organisms has the potential to produce clean energy. Bio-photoelectrochemical cells (BPECs) utilizing unicellular photosynthetic microorganisms have been studied, however similar harvesting of electrons from more evolved intact photosynthetic organisms has not been previously reported. In this study, we describe for the first time BPECs containing intact live marine macroalgae (seaweeds) in natural seawater or saline buffer. The BPECs produce electrical currents of >50 mA/cm2, from both light-dependent (photosynthesis) and light-independent processes. These values are significantly greater than the current densities that have been reported for single-cell microorganisms. The photocurrent is inhibited by the Photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, indicating that the source of light-driven electrons is from photosynthetic water oxidation. The current is mediated to the external anode via NADPH and possibly other reduced molecules. We show that intact macroalgae cultures can be used in large-scale BPECs containing seawater, to produce bias-free photocurrents, paving the way for the future development of low-cost energy solar energy conversion technologies using BPECs.
Keywords: Electrochemistry; Fluorescence; Hydrogen evolution; Photosynthesis; Seaweeds; Solar energy conversion.
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