Enzyme-based photoelectrochemical biofuel cell

Both dye-sensitized photoelectrochemical solar cells and biofuel cells are promising candidates for production of renewable energy. We have combined these two approaches into a single hybrid cell. The photoanode consists of a nanoparticulate SnO₂ electrode coated with a porphyrin sensitizer (S). Key to the operation of the cell is the coupling of the anode photoreactions to the oxidation of biological fuels such as glucose or alcohols by an NAD(P)H/NAD(P)⁺ redox carrier. Electron donation to the oxidized sensitizer S^·+ by NAD(P)H is facile, generating NAD(P)⁺, which is not reduced by charge recombination reactions at the photoanode. Enzymes oxidize the biological fuel and, in the process, reduce the NAD(P)⁺ coenzyme back to NAD(P)H. These reactions are coupled to cathodic redox reactions through an ion-permeable membrane in a two-compartment electrochemical cell. Hybrid cells of this general type have several potential advantages over either the photoelectrochemical cell or the biofuel cell operating individually.