Abstract
Oxygenic photosynthetic organisms perform solar energy conversion of water and CO2 to O2 and sugar at a broad range of wavelengths and light intensities. These cells also metabolize sugars using a respiratory system that functionally overlaps the photosynthetic apparatus. In this study, we describe the harvesting of photocurrent used for hydrogen production from live cyanobacteria. A non-harmful gentle physical treatment of the cyanobacterial cells enables light-driven electron transfer by an endogenous mediator to a graphite electrode in a bio-photoelectrochemical cell, without the addition of sacrificial electron donors or acceptors. We show that the photocurrent is derived from photosystem I and that the electrons originate from carbohydrates digested by the respiratory system. Finally, the current is utilized for hydrogen evolution on the cathode at a bias of 0.65 V. Taken together, we present a bio-photoelectrochemical system where live cyanobacteria produce stable photocurrent that can generate hydrogen.
Highlights
Oxygenic photosynthetic organisms perform solar energy conversion of water and CO2 to O2 and sugar at a broad range of wavelengths and light intensities
Cyanobacteria are a wide class of photosynthetic organisms that have been recently proposed as potential sources of materials from which photoexcited electrons can be extracted to produce electrical current and renewable fuels[1,2,3]
A proton-motive gradient is created between the thylakoid membrane lumen and the cytoplasm, resulting in proton-coupled electron transfer, which serves as the driving force for ATP production
Summary
Oxygenic photosynthetic organisms perform solar energy conversion of water and CO2 to O2 and sugar at a broad range of wavelengths and light intensities. Since no external mediating electron transfer molecules were added to the BPEC, we conclude that the source of the redox species identified in Fig. 2c is from within the Syn cells. These results demonstrated that PSI and not PSII is the photosystem that drives the photocurrent when iSyn cells are illuminated in the BPEC.
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