A practical Photoelectrochemical Cell Using Nonprecious Metal Electrodes

Abstract: Photoelectrochemical cells (PECs) can be used to harvest light from the oxidation of dissolved organic matter. Similar to fuel cells but requiring light to operate, PECs contain a light assisted electrode that oxidises electron rich materials (anode); these electrons then flow to a typically Pt cathode where O2 is normally the electron acceptor. In this work a PEC cell containing inexpensive materials was shown to (a) mineralise typical organic compounds present in waste water and (b) produce electricity from their decomposition. The PEC cell consisted of a TiO2 coated conducting ink anode exposed to a light source, and an air electrode as cathode. Isopropyl alcohol (IPA) and formic acid were degraded using the PEC cell. It operates most efficiently with a 150 W Xe source but also degrades ascorbic acid using a tungsten light source and catechol using daylight. All compounds were shown to degrade by zero order kinetics, and the PEC cell was shown not to work appreciably in dark conditions. IPA photoelectrodegraded at a rate of 706 mol L-1 s-1, almost 200 times faster than ascorbic acid. Unconnected (photochemical) and blank cells where shown to degrade organic compounds to a much lesser extent than connected ones, showing that photoelectrodegradation was a more thorough mechanism for organic mineralisation than simple photodegradation or photochemical degradation. Using a standard household bulb as light source, a formic acid PEC cell produced 19.1 ± 2 mW m-2 , and when the same cell was placed on a laboratory window sill a power of 31.5 ± 2 mW m-2 was recorded. As the PEC cell prototype presented here utilises inexpensive materials, there is a possibility of scale up for outdoor and commercial use.