PARENT SESSION
Posters P8D Artificial photosynthesis and biological hydrogen production. Abstracts (759-769)

Artificial photosynthesis and hydrogen production: Strategies for sustainable energy production. Thomas Moore^*,1, Ana Moore¹, Devens Gust¹, Michael Hambourger¹, Alicia Brune¹, ¹ Center for the Study of Early Events in Photosynthesis, Tempe, Arizona, USA

ABSTRACT- Energy security is an issue facing humanity that is no less significant than war, famine, disease, the plight of refugees and the guarantee of human rights across the lands. Nature's photosynthetic process provides inspiration for artificial photosynthetic constructs for sustainable global energy production and efficient energy transformations which can ensure energy security for all people. We have designed several artificial photosynthetic elements and assembled them into energy converting systems. For example, carotenoid pigments and polymer polyenes can be incorporated into tetrapyrrole-based artificial reaction centers. In certain of these systems coverage of the solar spectrum is large and in some cases antenna function of the polyene pigment is near 100% efficient. In more complex systems, liposome-based artificial ion pumps have been assembled that are based on Mitchellian redox loops and vectorial redox potential developed by artificial reaction centers; these constructs demonstrate net solar to chemical potential energy conservation. In an attempt to functionally mimic aspects of photofermentation, we have constructed a photoelectrochemical cell that oxidizes carbohydrates or alcohols, uses light to boost the reduction potential of the resulting electrons, and reduces protons to H₂ at neutral pH. The photoanode consists of a nanoparticulate TiO₂ electrode coated with a porphyrin sensitizer (P) which upon excitation injects an electron into the TiO₂ conduction band. This anodic photoreaction is coupled to the oxidation of biological fuels by electron donation from NADH to the oxidized sensitizer P^.+ ultimately generating NAD+. Dehydrogenase enzymes oxidize the biological fuel and reduce the NAD+ to NADH. The cathode comprises a composite of nanoparticulate platinum on carbon immersed in a buffer solution. In preliminary experiments, it was found that excitation of the photoanode with light absorbed only by the porphyrin results in evolution of gaseous hydrogen from the cathode with a quantum yield of ca 5%.

KEY WORDS: Energy Transfer, Artificial Photosynthesis, Biomimicry, Solar Hydrogen Production