Self-organized photosynthetic nanoparticle for cell-free hydrogen production

There is considerable interest in making use of solar energy through photosynthesis to create alternative forms of fuel. Here, we show that photosystem I from a thermophilic bacterium and cytochrome-c ₆ can, in combination with a platinum catalyst, generate a stable supply of hydrogen in vitro upon illumination. The self-organized platinization of the photosystem I nanoparticles allows electron transport from sodium ascorbate to photosystem I via cytochrome-c ₆ and finally to the platinum catalyst, where hydrogen gas is formed. Our system produces hydrogen at temperatures up to 55°C and is temporally stable for >85 days with no decrease in hydrogen yield when tested intermittently. The maximum yield is ∼5.5μmol H ₂ h_-1 mg_-1 chlorophyll and is estimated to be ∼25-fold greater than current biomass-to-fuel strategies. Future work will further improve this yield by increasing the kinetics of electron transfer, extending the spectral response and replacing the platinum catalyst with a renewable hydrogenase.