A self-assembling self-repairing microbial photoelectrochemical solar cell

Biologically-based approaches to large-scale solar power generation promise low cost durable technologies that will exhibit the self-repairing capabilities of photosynthetic organisms^1–3 (Basic Research Needs for Solar Energy Utilization, U.S. Department of Energy, Washington DC, 2005; J. Barber and B. Andersson, Trends Biochem. Sci., 1992, 17, 61; A. Huijser et al., J. Phys. Chem. C, 2007, 111, 11726). Most proposed approaches however utilize photosynthetic proteins extracted from organisms^4–6 (S. A. Trammell et al., J. Phys. Chem. C, 2007, 111, 17122; R. Das et al., Nano Lett., 2004, 4, 1079; E. Greenbaum, Science, 1985, 230, 1375) and forgo the self-repair capabilities of organisms resulting in short-lived power generation. Beginning with two non-descript graphite electrodes and marine sediment and seawater, we report here a proof-of-concept demonstration of a self-assembling and self-repairing microbial photoelectrochemical solar cell that generates electricity from sunlight⁷ (S. A. Licht, Nature, 1987, 330, 148). Time records of voltage and current generated by this solar cell reveal a circadian rhythm consistent with a photosynthetic nature. This result supports the interpretation that the electrode reactions are catalyzed by self-maintaining biofilms spontaneously formed on each electrode surface, and that the electrode reactants are photosynthetically regenerated from the electrode products by a self-maintaining spontaneously formed photosynthetic consortium. Our finding suggests a strait-forward approach toward durable biologically-based solar power generation.