Operating at ~ 150 TW of net primary production, photosynthesis powers the biosphere and supports most of life on Earth. Today, estimates of the human appropriation of biomaterials range from 20 to 35% of terrestrial photosynthetic net primary production. This impacts the biosphere because, on the geological time scale, ecosystems evolved to make use of essentially all of the solar energy input; it raises the issue of competition between the human species and the rest of the biosphere. In other words, it can be argued that there are no significant reserves of photosynthetic capacity or solar energy to meet the needs of the expanding human population. Indeed, when additional demands on photosynthesis are made, the capacity to meet them comes at the peril of biosphere service and support, pushing Earth's ecosystems further from a sustainable trajectory. Photosynthesis, optimized by Darwinian selection to move genes forward, does not produce biomass efficiently. Fortunately, photosynthetic efficiency can be dramatically improved. Photovoltaic technology uses thermodynamic principles that apply to the conversion of light into chemical and/or electrical potential combined with advances in materials and strategies to achieve record efficiencies. In selected photosynthetic systems, rational design based on the principles developed in artificial systems can be used to optimize conversion efficiencies to meet particular needs. This presentation will cover examples using design principles derived from biological systems to engineer redox relays that improve the efficiency of hole transfer from oxidized dyes to water oxidizing catalysts in photoelectrochemical cells. As in photosynthesis, the redox relay serves to couple the fast kinetics associated with primary photochemistry to the relatively slow kinetics of hole transfer to the catalyst. Additionally, progress will be reported on a tandem cell that uses junctions and antennas optimized for water redox to oxygen and hydrogen or reduced carbon production.

Artificial photosynthesis and bio-inspired solar-to-fuel strategies

246th National Meeting (2013)

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