Artificial photosynthesis: Combining technology with biology for efficient solar energy conversion

Provided significant challenges can be met, solar powered, bio-inspired constructs can contribute to renewable energy resources to meet human energy needs. The central challenge is reversing the combustion process by efficient water oxidation and reductive synthesis of CO2 to fuels. Nature's catalysts direct these oxidation/reduction reactions along coordinates that have low activation barriers and almost no side reactions. In principle, these reactions can be driven by electricity provided by sustainable sources. In order to accomplish this, it will be necessary to switch nature's catalysts from their usual source of redox potential - electron/proton carrying redox species - to emf at appropriate electrical potentials. Taking a step in this direction, we have assembled a hybrid system in which a porphyrin-sensitized Grätzel-type nanoparticulate wide band gap semiconductor photoanode is used as an interface between emf and redox potential for the photochemical reformation of biomass to hydrogen.