Solar-driven microbial photoelectrochemical cells with a nanowire photocathode.

We report a self-biased, solar-driven microbial photoelectrochemical cell (solar MPC) that can produce sustainable energy through coupling the microbial catalysis of biodegradable organic matter with solar energy conversion. The solar MPC consists of a p-type cuprous oxide nanowire-arrayed photocathode and an electricigen (Shewanella oneidensis MR-1)-colonizing anode, which can harvest solar energy and bioenergy, respectively. The photocathode and bioanode are interfaced by matching the redox potentials of bacterial cells and the electronic bands of semiconductor nanowires. We successfully demonstrated substantial current generation of 200 μA from the MPC device based on the synergistic effect of the bioanode (projected area of 20 cm2) and photocathode (projected area of 4 cm2) at zero bias under white light illumination of 20 mW/cm2. We identified the transition of rate-limiting step from the photocathode to the bioanode with increasing light intensities. The solar MPC showed self-sustained operation for more than 50 h in batch-fed mode under continuous light illumination. The ability to tune the synergistic effect between microbial cells and semiconductor nanowire systems could open up new opportunities for microbial/nanoelectronic hybrid devices with unique applications in energy conversion, environmental protection, and biomedical research.