A photoactivated fuel cell used as an apparatus that consumes organic wastes to produce electricity

Abstract

A two-compartment photoelectrochemical cell has been constructed and employed as a photoactivated fuel cell that can consume organic material to produce electricity. The cell comprises of a fluorine-doped tin oxide transparent anode electrode supporting a nanocrystalline titania photocatalyst, a Pt/carbon-black electrocatalyst deposited on a carbon cloth as the cathode and a porous membrane (glass frit) separating the two compartments. Both the anode and cathode compartments contain 1.0 M NaOH, but the anode compartment also contains the photodegradable organic substance. The cell runs without any external bias, only by UVA (black light) irradiation or by natural solar light. Glycerol and two higher polyols, xylitol and sorbitol, were tested as fuels. Both the open-circuit voltage and the short-circuit current depended on the polyol concentration up to a saturation value. The maximum current density was around 0.8 mA cm⁻², calculated over the anode active geometrical area, and maximum open-circuit voltage was around 1.3 V. For quasi-monochromatic incident radiation (363 nm wavelength), the above maximum current density corresponded to an external quantum efficiency (IPCE%) of 77%. The fill factor of the cell was relatively small but improved when a thin cell design was applied. All three studied polyols gave similar data for the same molar concentration, suggesting that photodegradation possibly proceeds by steps affecting a single hydroxyl group at a time.